Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: Nick Rains on September 04, 2009, 07:28:54 pm
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A recently closed thread - which degenerated into acrimony - was 'discussing' whether a wide lens has the same perspective as a series of stitched, longer focal length images covering the same FOV from the same postion.
Now, I know the theory from books, and I've been shooting for 26 years so I know the real world too. However, I'm now puzzled and could do with enlightenment without being yelled at.
DoF - this is the same for any lens at a given f stop and depends entirely on the subject distance from the camera. That much I know and I think we all agree on both the theory and the practice.
But the perspective, if that's the right word, is not the same with a single wide lens as it is with a series of stitched narrower FOV shots. I was fiddling around with a zoom lens - 17-40 - and the relationship of objects in corners of the 17mm setting looks totally different compared to the same items from the same position at the 40mm setting. I can only conclude that a single shot with the 17mm will look completely different than that from a stitched series using the 40mm setting taken from the same position.
This is what Guy Mancuso was alluding to, before he was shouted down.
I read the thread and was going with ThierryH's theory at first until I read Guy's post with the 28mm interior shot divided into 6 panels. It's quite clear that the look of each of those panels is not the same as from a lens of longer FL that covers the same region of the subject.
I'm not totally sure why, but it's clearly the case - maybe it's to do with the fact that a wide lens has 'bend' the light a lot to project such a wide FOV onto the sensor as a single image, whereas the longer lens has to bend the light less - less distortion.
In fact the more I think about it, the more sure I am that it's to do with having to move the camera to take the stitched images. Therefore the relationship between the camera and the subject is not the same as with a single capture. The only stitched images that have the same persepective as a single capture with the same FOV are those captured with a shift lens where the camera is not moved, only the lens. I suggest that a (hypothetical) 90mm shift lens which could be shifted to cover the same total FOV as a 28mm lens would look exactly the same as single capture from the 28mm lens. OTOH, a series from a fixed 90mm lens where the camera had to be rotated would not look the same.
I'm no optical expert but I know what I see. The perspective similarity between stitched images and equivalent wide lenses is mostly a myth. It's only true if the camera does not move at all - not just its position but it's orientation to the subject.
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Are you referring to geometric distortion? This distortion may not appear in the individual shots with the longer focal length lens, but when the images are stitched together and the rectilinear geometric transformation applied, the end result will be the same. (This ignores other issues such as the polyhedral focus of stitched images versus the normal focal 'plane').
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I was fiddling around with a zoom lens - 17-40 - and the relationship of objects in corners of the 17mm setting looks totally different compared to the same items from the same position at the 40mm setting. I can only conclude that a single shot with the 17mm will look completely different than that from a stitched series using the 40mm setting taken from the same position.
Nick, what about posting those images for others to chew on, in good resolution and quality if possible, together with the stitched result?
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Are you referring to geometric distortion? This distortion may not appear in the individual shots with the longer focal length lens, but when the images are stitched together and the rectilinear geometric transformation applied, the end result will be the same. (This ignores other issues such as the polyhedral focus of stitched images versus the normal focal 'plane').
Maybe that's the term I was fishing around for. I believe you have it right here.
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Nick, what about posting those images for others to chew on, in good resolution and quality if possible, together with the stitched result?
This was the thread:
http://luminous-landscape.com/forum/index....40&start=40 (http://luminous-landscape.com/forum/index.php?showtopic=37346&st=40&start=40)
The image I'm referring to is towards the end of P3.
I didn't shoot any images with the zoom, just looked through the viewfinder; grab a camera and you'll see what I mean. If I have time I'll shoot the frames but I'm ducking back to the computer between Saturday morning chores around the house!
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First it's probably a good idea to agree on some terminology. What I would call geometric distortion has nothing to do with perspective or even focal length, except to the extent that certain focal lengths tend to have certain types of geometric distortion due to lens design contraints. Namely, telephotos often have pincushion, while wide-angle lenses are more likely to have barrel distortion. These distortions are optical flaws in lenses though, and have nothing to do with perspective. In fact two 20mm lenses can have varying amounts of barrel distortion.
Geometric distortion is not what causes elements at the edge of a wide-angle shot to be stretched out. That's rectilinear distortion, or perspective distortion (I've seen it called both). Rectilinear distortion has everything to do with perspective and field of view. Note I said field of view, not focal length. Whether you get that perspective and field of view from a single wide-angle shot or by shooting several shots with a longer lens and then stitching them using a rectilinear projection, the resulting perspective will be the same.
It's true that if you just take several shots with a longer lens and align them you won't get the same look as a wide-angle shot. But that's not what pano software does; it projects the images, and as part of that process the outer portions of the resulting image will get stretched just like they do in a wide-angle shot. The wider the field of view, the more the edges are stretched; which is why even though you can shoot a much wider FOV with stitching than with the widest of lenses, you probably won't want to use a rectilinear projection for extreme FOV's. Note that other projections such as cylindrical or spherical do not produce the same results as a rectilinear projection.
You don't need panos/stitching to prove that perspective is determined solely by position and not focal length. Take a zoom lens such as the 17-40 and mount it on a tripod. Take a shot at 17mm, and another at 40mm. On the computer, crop the 17mm image so that it covers the same part of the scene as the 40mm image, and you'll find that the perspective of the two resulting images (eg the spatial relationships and relative sizes of objects in the scene) will be exactly the same. I think DPReview even has an article covering this with sample shots if you don't feel like doing the experiment yourself. It's incontrovertible fact, and it really does amaze me how many photographers refuse to grasp this concept. Usually it's 35mm photographers who had never shot any other formats before digital came along, and you'll hear them saying something like "I don't like DX format because I can't use a 60mm lens to get the same pleasing portrait perspective that my 85mm lens gave me on 35mm". Try shooting that 85mm portrait on 4x5" film and then tell me that it's the focal length that determines the perspective....
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I didn't shoot any images with the zoom, just looked through the viewfinder; grab a camera and you'll see what I mean
I thought you actually made the shots. As I understand it now, you found the corner of the 17mm shot visually different from the 40mm shot of that corner. You were right.
1. When you make a shot at 17mm and then at 40mm from the same position, in the same direction, then the respective crop of the 17mm image will be identical (regarding the perspective) to the 40mm shot. Geometric distortion may play some role, but that's not "perspective".
2. When you make a 17mm shot and then you shoot the corner of that frame with 40mm, you have to adjust the camera's direction. The lens is rectilinear, it captures a rectangle perpendicular to the lens' axis. This will look very different from the corner of the 17mm shot.
It is the job of the stitcher to warp the source frames, so that they look like they had been part of a larger frame, presumed you choose rectilinear projection (as its name suggests, the rectilinear projection creates a single rectilinear mosaic/pano). Thus the result of stitching won't look like what you saw in the viewfinder.
Added: there is lots of overlap with Jeff's post above; we must have been typing at the same time.
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the result of stitching won't look like what you saw in the viewfinder.
Thanks for that, great way to putting it! More than once have had this discussion with other photographers. My response is always "well, just try it, you'll be convinced!" Apparently nobody wants to do anything more than just look through the viewfinder.
Should also be noted that most stitchers now offer extremely useful projections and hybrid projections that are simply unavailable with any lens. Some of these easily solve thorny problems with super wide shots.
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Should also be noted that most stitchers now offer extremely useful projections and hybrid projections that are simply unavailable with any lens. Some of these easily solve thorny problems with super wide shots.
Yes, I really like the Vedutismo projection in PTGui for landscapes. I tend to use that for anything too wide to look natural with a rectilinear projection.
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Just to confuse things further, the geometric 'look' of the final stitched image will depend on the kind of projection chosen to render the stitch into a single image.
I have assumed (never tested) that a planar projection of a stitched set of images from a longer lens that covers the same FOV as a wide lens will have the same geometric properties as the single frame from the same wide lens.
The Geometric 'look' (maybe sometimes confused with perspective?) will vary quite a lot if a spherical or cylindrical projection is chosen.
Cheers
Murray
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Nick,
I was sorry to see that thread degenerate to that point as well. I believe the problem some were having with it is confusing distortion and perspective.
I also believe the problem some are having with this concept is related to how we are so entrenched in using focal length to control perspective, but we forget to do so we also have to change positions. If we do not change positions, we actually don't change perspective, we change the field of view. But because we are so entrenched in the idea of using longer lenses to change perspective, we believe using stitching to increase the field of view to match, we will get the benefit if the perspective change from using the longer lens ... it sort of sounds logical. It doesn't work that way ... perspective only changes when the camera position changes, not when the focal length changes.
In effect when using stitching we are increasing the size of the the sensor ... we are creating a "larger format" camera and thus require a longer lens and several stitched images to match the FoV. but to change perspective you still have to change the position of the camera. You cannot use stitching with a longer lens as a method to change perspective. It really is just the basic physics.
The picture you mentioned is a good example. Were that picture taken with a longer lens capturing only 1/6th of the field of view, and then stitched, the perspective would remain the same. What in effect you are doing is using a larger format camera (stitched = greater sensor size), and thus needing a longer lens to narrow the FoV to match.
Distortion can certainly be a problem, but distortion and perspective are not the same thing . This is especially the case with close foreground objects and/or wide angle lenses. But if the lens distorted the perspective, it isn't actually "valid" (if I dare use that term). IF you correct out the distortion, then the images match.
I never thought about this much, but accidently learned this by first hand experience several years ago. I was taking a picture using of a golf green in the foreground and the clubhouse in the background. I wanted to change the perspective to increase the size of the clubhouse in relation to the green but couldn't get further away (without a helicopter). So I decided to use a 200mm lens to stitch an image together, believing it would accomplish the same thing. To my surprise, the final stitched shot was virtually identical to the one I took with my 80mm lens. Because neither focal length was a wide angle there wasn't even any evidence of problems with distortion. So the only way I could change the perspective of the golf hole to the clubhouse would be to use the 200mm lens, and move farther away until the golf hole was the same size. Only then would my clubhouse become larger in perspective. Since I didn't have a helicopter at my disposal I didn't get the shot.
I hope I'm not being over simplistic. It's sure easy to go out and try it for yourself.
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It is the job of the stitcher to warp the source frames, so that they look like they had been part of a larger frame, presumed you choose rectilinear projection (as its name suggests, the rectilinear projection creates a single rectilinear mosaic/pano). Thus the result of stitching won't look like what you saw in the viewfinder.
Thanks, I guess that's the missing point - stitching software will warp images to match the chosen projection and if you want a flat projection taken with multiple shots it will warp the corners to look like that of an equivalent wide angle lens. The w/a is doing the same job, 'warping' the image into a flat projection onto the sensor.
If a cylindrical projection works for you, then you'll get a different look, more like the old Noblex cameras used to get.
This is where the "textbook" theories of perspective, distortion etc get confusing - they have to be tempered with what you are actually doing with the shots in post i.e. how they will be projected onto the flat surface of a screen or print.
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Quick test in a corner of my living room (full size samples).
- Comparison between single frame with 24 mm lens and 3 rows pano with 60 mm lens,
- The camera was in the exact same position, I kept it on the pano head in both samples, just switched the lens and set the pano head to central position for the 24 mm lens,
- distance to the subject is less than 1 meter (about 70 cm),
- Focus was set with live view on the book next to the fan,
- Both images were shot in M mode at f8,
- The pano was computed with PTgui in flat projection mode,
- It took about 40 seconds to shoot the pano without trying to be utterly fast, this is the result of my first and only trial,
- The computation of the pano took less than 10 minutes for this 120 megapixel image.
- single image from a 24 mm lens, slightly cropped to match the stitch result (22 megapixel):
(http://farm3.static.flickr.com/2495/3887923847_bf64623c7b.jpg)
(link to jpg quality 8, 2.5 MB full size image) http://www.flickr.com/photos/bernardlangui...923847/sizes/o/ (http://www.flickr.com/photos/bernardlanguillier/3887923847/sizes/o/)
- pano made with a 60mm lens, 3 rows of 4 images (120 megapixel).
(http://farm3.static.flickr.com/2659/3888724060_42821045e3.jpg)
(link to jpg quality 7, 7.5 MB full size image) http://www.flickr.com/photos/bernardlangui...724060/sizes/o/ (http://www.flickr.com/photos/bernardlanguillier/3888724060/sizes/o/)
What I see:
- the sensor of my d3x needs cleaning,
- the images are very similar,
- the pano image has less DoF since it was shot with a longer lens.
- the 24 mm lens has some geometrical distorsion that is not visible in the pano image. this is not a simple spherical one and results in subtle differences in rendition of some of the objects. Both scenes would probably be assessed by 99% of people to be totally faithful to the original.
- the 24 mm lens has some light fall off event at f8 (see upper left corner),
- the color rendition of the 24mm appears to be a bit more neutral than that of the 60mm, although this difference could also have been introduced by the pano software,
- the sharpness per pixel of the pano is on par with that of the single image and can be considered to be excellent in absolute terms.
My personal conclusion are:
- real world usage matches the theory very well, flat projection panos are difficult to distinguish from single frames shot with a wide lens,
- when high resolutions are needed for an application pano are a handy solution, the impact in shooting time is small (think of all the other things you would have had to do before taking this image) but processing time can be a problem.
Cheers,
Bernard
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Attached the top left and the top right corner shots of a 2x7 shot pano, in rectilinear projection. This is the work of the warping. These show, that the shot of the corners captured a larger area than the wider lens would have captured. This means, that only a part of this frame becomes part of the pano, and that part needs to be stretched in order to achieve the same proportions as a single rectilinear shot would have created.
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The only stitched images that have the same persepective as a single capture with the same FOV are those captured with a shift lens where the camera is not moved, only the lens.
This also applies to images stitched using a sliding back (or rear standard movements) on a view camera, where not the lens, but the sensor is moved. This produces much better results if any part of the subject is near the lens.
...but the theory is that the stitching software e-projects the images to try to correct the perspective.
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This also applies to images stitched using a sliding back (or rear standard movements) on a view camera, where not the lens, but the sensor is moved. This produces much better results if any part of the subject is near the lens.
...but the theory is that the stitching software e-projects the images to try to correct the perspective.
Do you have any concrete comparison showing that the leading softwares are unable to do it? I believe that my post above in this thread clearly shows that there is at least one example where they do an excellent job.
My question is geniune, I have never seen such a case, but it could very well exist.
Cheers,
Bernard
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Hi,
The way I see it if we discuss really wide images rectilinearity is an illusion. It comes from the way the brain interprets images, it knows that structures are rectilinear. Add to this that the non peripheral field of seeing is rather small, what we see sharp is always within a small angle.
To keep parallel lines straight and parallel we need to to distort (stretch out) images which are of axis (that is seen with a large angle of view). So for wide angle panoramas we either have to stretch out the peripheral part, thus distorting surfaces, or accept curved and converging parallels by using cyclindrical or spherical projection.
A rectilinear wide angle does this stretching internally, a panorama camera using a swinging lens gives a cylindrical panorama and a fish eye a spherical one.
When stitching we can choose either mapping, except for very wide angles where rectilinear projection is not possible because it would need infinite stretching.
Best regards
Erik
A recently closed thread - which degenerated into acrimony - was 'discussing' whether a wide lens has the same perspective as a series of stitched, longer focal length images covering the same FOV from the same postion.
Now, I know the theory from books, and I've been shooting for 26 years so I know the real world too. However, I'm now puzzled and could do with enlightenment without being yelled at.
DoF - this is the same for any lens at a given f stop and depends entirely on the subject distance from the camera. That much I know and I think we all agree on both the theory and the practice.
But the perspective, if that's the right word, is not the same with a single wide lens as it is with a series of stitched narrower FOV shots. I was fiddling around with a zoom lens - 17-40 - and the relationship of objects in corners of the 17mm setting looks totally different compared to the same items from the same position at the 40mm setting. I can only conclude that a single shot with the 17mm will look completely different than that from a stitched series using the 40mm setting taken from the same position.
This is what Guy Mancuso was alluding to, before he was shouted down.
I read the thread and was going with ThierryH's theory at first until I read Guy's post with the 28mm interior shot divided into 6 panels. It's quite clear that the look of each of those panels is not the same as from a lens of longer FL that covers the same region of the subject.
I'm not totally sure why, but it's clearly the case - maybe it's to do with the fact that a wide lens has 'bend' the light a lot to project such a wide FOV onto the sensor as a single image, whereas the longer lens has to bend the light less - less distortion.
In fact the more I think about it, the more sure I am that it's to do with having to move the camera to take the stitched images. Therefore the relationship between the camera and the subject is not the same as with a single capture. The only stitched images that have the same persepective as a single capture with the same FOV are those captured with a shift lens where the camera is not moved, only the lens. I suggest that a (hypothetical) 90mm shift lens which could be shifted to cover the same total FOV as a 28mm lens would look exactly the same as single capture from the 28mm lens. OTOH, a series from a fixed 90mm lens where the camera had to be rotated would not look the same.
I'm no optical expert but I know what I see. The perspective similarity between stitched images and equivalent wide lenses is mostly a myth. It's only true if the camera does not move at all - not just its position but it's orientation to the subject.
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It's why there was the argument yesterday -- I think folks are talking apples to oranges to bananas. You have perspective, lens distortions and 3D>2D image projections. They all affect how the image will appear.
Regardless, the fact remains that for visual PERSPECTIVE, the only thing that affects it are the relative positions of the shooter to subject. Lens distortions and/or projection conversion will alter how the image appears but will not alter that relative perspective...
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Regardless, the fact remains that for visual PERSPECTIVE, the only thing that affects it are the relative positions of the shooter to subject. Lens distortions and/or projection conversion will alter how the image appears but will not alter that relative perspective...
(Bolding mine)
Ding Ding Ding...we have a winner....
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To Nick Rains,
I stitch ALL the time. I went through a period where I stitched every frame I shot, even people shots, even handheld people shots. I did it with the Canon 45TS. That's the only lens I have any experience with, stitching. But I love the results. I don't care about any of these fancy terms about distortion -- call it what you want. I could care less. I only care about the photograph and the resulting image. I just know that the 45 stitched produces a much more pleasing image than moving in closer with a wide angle, with its "womp factor". I like to stay back a bit, and leave things flatter optically, and then stitch by shifting the 45. Ideally, you'd Liquid Nails a tripod mount onto the 45 lens, and mount the lens onto the tripod, rather than the body. That way, if on a tripod, it would line up to the pixel, in post. But even with the body mounted, (wrong technique), it's pretty easy to stitch in post if you have large overlap. I simply prefer the flatter look, even when you add in the additional post work.
I stitch with the 80 too, on the H2, but since it's not a shift lens, it's a much bigger task, even with that stupid RRS attachment. Simply put, if you pan the body, you're asking for trouble, in post. No matter what gadget or nodal point you're using. Just one opinion.
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...but the theory is that the stitching software e-projects the images to try to correct the perspective.
Do you have any concrete comparison showing that the leading softwares are unable to do it? I believe that my post above in this thread clearly shows that there is at least one example where they do an excellent job.
My question is geniune, I have never seen such a case, but it could very well exist.
Cheers,
Bernard
Bernard...
I am not trying to pick an argument with you or anyone.
I agree that your post above in this thread clearly shows that stitching programs do an excellent job... and these low-res (versions of your) pictures prove your point about perspective, but they do not prove that a 100 Mpx rectilinear pan-and-stitch (e.g.Nikon) DSLR image is as sharp as a 100 Mpx shift-and-stitch image created with a MFDB like a P65+ or a H3D22-60 with a view camera.
Any process that re-sampls an image, projects it, or passes an image through another piece of glass is bound to decrease resolution... but this effect might be imperceptible.
I appreciate that a cylinder pano pan-and-stitch image often looks better than anything you could achieve with a single shot camera (ignoring the Seitz roundshot), and I expect to use my MFDSLR or view camera for pan-and-stitch where appropriate.
I hope that in a few days I will have live view working on my camera, and I will be able to produce some test images.
One effect of pan-and-stitch or computer perspective (converging verticals) correction e.g. in tall buildings is that the resultant image is truncated in the direction of the converging lines... of course it might be possible for the stitching software to compensate for this, or you could manually stretch (PS distort) the image, but this too would tend to slightly degrade the image.
It you want to think of viewpoint perspective, think of a Kamara Obskura (there is one just up the road at Compton Verney) or a pin hole camera, and eliminate any thoughts about lens distortion.
View-point perspective...
In a (1980) Calendar shot of a tractor mounted mower I wanted the hill in the background to look bigger in relation to the tractor... and I was fortunate that I was able to use the telephoto instead of the standard lens: this evolved having the camera within two feet of the ground to get the hill in the right place relative to the tractor, but it produced the desired result.
Now... if I do not get out and mow the lawn my wife will not be happy.
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This is actually an interesting argument, which reminds me of some basic theories of Optics I learned in high school and undergraduate (BTW, my background is engineering and physics). It's true some great photographers might not be proficient in such theories, and it does not mean photographers with handful theories are excellent either. Most of us learn these stuff from practice. Yes, seeing is believing, right? Happy shooting!
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This is a pretty good write-up (with pictures) on the subject.
http://photography-on-the.net/forum/showth...dof+perspective (http://photography-on-the.net/forum/showthread.php?t=672913&highlight=dof+perspective)
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To me, it's simple. Set the tripod and camera to the position that gives the desired perspective/composition. Choose the lens that will give the desired detail (resolution), which also dictates how many frames will be needed. If you don't have a lens that will cover the FOV in one image you will need to stitch. If more detail is desired than a short focal length lens will produce, use a longer focal length.
For in-camera composition fanatics, set the composition with a wide angle lens, then use a longer focal length lens to gain the detail (resolution).
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they do not prove that a 100 Mpx rectilinear pan-and-stitch (e.g.Nikon) DSLR image is as sharp as a 100 Mpx shift-and-stitch image created with a MFDB like a P65+ or a H3D22-60 with a view camera
The stitched result from DSLR shots can be less or more sharp than the MFDB shots. It depends not only on the DSLR camera (and lens quality), but on the selected focal length. One can choose a lens, which gives a much higher overall resolution than the MFDB shot; the interpolation of the warping process will be better, if shrinking instead of stretching is involved. In other words, a 100 Mpix pano can be created from 200 Mpix sources plus overlaps.
Note, that the source frames of the stitching should never be sharpened, except for scene referred sharpening if starting out with raw images; only the finished pano should be sharpened.
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The stitched result from DSLR shots can be less or more sharp than the MFDB shots. It depends not only on the DSLR camera (and lens quality), but on the selected focal length. One can choose a lens, which gives a much higher overall resolution than the MFDB shot; the interpolation of the warping process will be better, if shrinking instead of stretching is involved. In other words, a 100 Mpix pano can be created from 200 Mpix sources plus overlaps.
Note, that the source frames of the stitching should never be sharpened, except for scene referred sharpening if starting out with raw images; only the finished pano should be sharpened.
If you do a rectilinear shift-and-stitch with a digital back and a good lens, and print direct from the original file at your printer's best dpi there is no scaling, stretching or warping, (both the H3D11-60 and the P65+ will print 24" @ 360 original camera pixels per print inch). You might need to pan-and-stitch 400 Mpx to look as good as a 100 Mpx MF shift-and-stitch.
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You might need to pan-and-stitch 400 Mpx to look as good as a 100 Mpx MF shift-and-stitch.
I'm afraid this is speculation without any factual basis.
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Bernard...
I am not trying to pick an argument with you or anyone.
I agree that your post above in this thread clearly shows that stitching programs do an excellent job... and these low-res (versions of your) pictures prove your point about perspective, but they do not prove that a 100 Mpx rectilinear pan-and-stitch (e.g.Nikon) DSLR image is as sharp as a 100 Mpx shift-and-stitch image created with a MFDB like a P65+ or a H3D22-60 with a view camera.
Hi Dick,
This thread is not about quality, it is about the ability of stitching softwares to deliver results that are geometrically similar to those of a single lens. It is also about confirming with facts that theory that perspetive is only affected by camera/subject and that wide angle lenses do not bring any magic quality to the table.
As far as quality goes, there are links to full size versions of the images in my post as well. I keep thinking that we are very close to backs at pixel level, but we don't need to be. I could have shot this with a 100mm lens, it would have taken 3 times the time and the resolution would have been 3 times higher.
Cheers,
Bernard
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You might need to pan-and-stitch 400 Mpx to look as good as a 100 Mpx MF shift-and-stitch.
I agree that you will indeed need more pixels from a well executed D3x stitch to equal the sharpness of a back, but 4 times more?... I would be interested in hearing where you got this figure from.
Assuming that everything was done perfectly on both sides, my view is that the ratio is probably never higher than 1.5 even when comparing files on screen, and even lower when comparing prints. I was pretty amazed a few months ago to see that a 70cm wide pano printed awesomly well although the individual d2x images making it up had suffered from significant blur because of a tripod mount issue.
Considering that focusing a back very accurately in the field is not an easy task, there are in fact probably many real world cases where the ratio is close to 1 or even smaller than 1.
Anyway, I'll be spending the required 800 US$ in the coming weeks to rent a P65+ with a recent Mamiya lens and do my own comparison. I will be honnest about what I see.
Cheers,
Bernard
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You might need to pan-and-stitch 400 Mpx to look as good as a 100 Mpx MF shift-and-stitch.
I agree that you will indeed need more pixels from a well executed D3x stitch to equal the sharpness of a back, but 4 times more?... I would be interested in hearing where you got this figure from.
This is speculation without any factual basis, and this is why I used the word "might"... but, as always, it depends if you are comparing apples with apples... or comparing a picture produced from several pan-and-stitch stretched images taken with a camera with and anti-aliasing filter with one from two shift-and-stich images taken with an AA free camera. To evaluate the pan-and-stitch process, we would need to use the same quality of camera for both pictures.
I think that 4* might be correct for comparing a MFDB/apo digitar 210mm image with a stitched image from a 480mm large format sheet film lens, even if it was shift-and-stitched. I hope to be acquiring an apo-digitar 210 sometime soon, and I have a 480.
Assuming that everything was done perfectly on both sides, my view is that the ratio is probably never higher than 1.5 even when comparing files on screen, and even lower when comparing prints.
Considering that focusing a back very accurately in the field is not an easy task, there are in fact probably many real world cases where the ratio is close to 1 or even smaller than 1.
The focusing on the H3D is OK, and I do not expect to do much view camera work without live view.
Anyway, I'll be spending the required 800 US$ in the coming weeks to rent a P65+ with a recent Mamiya lens and do my own comparison. I will be honnest about what I see.
Cheers,
Bernard
We look forward to
I have started a thread to compare the P65+ to the H3D11-60.
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I dont know why you guys act so complicated because this side-issue is trivial. Bernard is of course right. Oversampling (downrezzing) solves everything. It's obvious that you can get every quality from it, even exceeding MFDB, no doubt.
From my experience with pixels I can tell I need maybe a 50-75% downres along with some sharpening gets me really high qualtity samples. If I want to achieve the ultimate pixel quality I ofc want to downsample as much as possible, through there is a point where you dont get much benefit beyond. That depends on the source image, but generally I'd say, 65% gets you pretty close to perfect. I dont own a MFDB, but this is common knowledge if you push your pixels and are used to look at the pixel level.
I mean thats exactly one advantage of stitching, you just massively oversample at shooting time. So you can get from a much much lower camera exactly the same or much better resolution than from a much more expensive cam. Trivial. Oversampling solves everything, so its just the question how much data you want/can/afford to practically capture regarding processing and storage. And for inferior source pixel sharpness of smaller cams, from a certain downscale factor on you just cant tell.
The disadvantage of achieving such high quality from smaller sensors is of course that you have to shoot very big and to downsample quite a bit. Depends on circumstances and camera.) But if you do this, you indeed end up with very very high quality files equal to or exceeding mfdb. I can say this without owning a mfdb because the quality I get when I downsample image data gets equal to my renderings. And rendered files, this is the cleanest quality you will **ever** get.
Christian
//Edit: And I could even understand if someone where a bit frustrated about it. If I own an expensive system and then realize I could pretty much workaround with lower tech stuff to get the same q results in some/many instances (or maybe in nearly all instances given my work)... And if I (maybe) only need the big MFDB file seldom... And if I had to struggle to get my high end system... then the issue could indeed be frustrating for me!
And I dont argue against mfdb - that would be CHILDISH. Its just and only about the quality issue in this particular regard in this particular discussion.
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I think to understand the question under discussion, it's is mandatory and sufficient to understand about image projections in pano stitching software. A great place to learn about these topics: PT Assembler projections (http://www.tawbaware.com/projections.htm).
With PT Assembler one can even transform one single image from its rectilinear original state (straight from the camera+rectilinear lens), into any other kind of projection. This is sometimes very interesting for example in strongly distorted WA shots to make them more pleasant to the eye. Moreover you learn a lot in the process.
Regards.
PS: I agree Bernard's sensor has some dust in it.
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PS: I agree Bernard's sensor has some dust in it.
At least one person is following!
Cheers,
Bernard
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Jeff,
Thank you for the comprehensive reply. I think you have summed up the answer to Nick's question very nicely.
-Brad
First it's probably a good idea to agree on some terminology. What I would call geometric distortion has nothing to do with perspective or even focal length, except to the extent that certain focal lengths tend to have certain types of geometric distortion due to lens design contraints. Namely, telephotos often have pincushion, while wide-angle lenses are more likely to have barrel distortion. These distortions are optical flaws in lenses though, and have nothing to do with perspective. In fact two 20mm lenses can have varying amounts of barrel distortion.
Geometric distortion is not what causes elements at the edge of a wide-angle shot to be stretched out. That's rectilinear distortion, or perspective distortion (I've seen it called both). Rectilinear distortion has everything to do with perspective and field of view. Note I said field of view, not focal length. Whether you get that perspective and field of view from a single wide-angle shot or by shooting several shots with a longer lens and then stitching them using a rectilinear projection, the resulting perspective will be the same.
It's true that if you just take several shots with a longer lens and align them you won't get the same look as a wide-angle shot. But that's not what pano software does; it projects the images, and as part of that process the outer portions of the resulting image will get stretched just like they do in a wide-angle shot. The wider the field of view, the more the edges are stretched; which is why even though you can shoot a much wider FOV with stitching than with the widest of lenses, you probably won't want to use a rectilinear projection for extreme FOV's. Note that other projections such as cylindrical or spherical do not produce the same results as a rectilinear projection.
You don't need panos/stitching to prove that perspective is determined solely by position and not focal length. Take a zoom lens such as the 17-40 and mount it on a tripod. Take a shot at 17mm, and another at 40mm. On the computer, crop the 17mm image so that it covers the same part of the scene as the 40mm image, and you'll find that the perspective of the two resulting images (eg the spatial relationships and relative sizes of objects in the scene) will be exactly the same. I think DPReview even has an article covering this with sample shots if you don't feel like doing the experiment yourself. It's incontrovertible fact, and it really does amaze me how many photographers refuse to grasp this concept. Usually it's 35mm photographers who had never shot any other formats before digital came along, and you'll hear them saying something like "I don't like DX format because I can't use a 60mm lens to get the same pleasing portrait perspective that my 85mm lens gave me on 35mm". Try shooting that 85mm portrait on 4x5" film and then tell me that it's the focal length that determines the perspective....
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You don't need panos/stitching to prove that perspective is determined solely by position and not focal length. Take a zoom lens such as the 17-40 and mount it on a tripod. Take a shot at 17mm, and another at 40mm. On the computer, crop the 17mm image so that it covers the same part of the scene as the 40mm image, and you'll find that the perspective of the two resulting images (eg the spatial relationships and relative sizes of objects in the scene) will be exactly the same. I think DPReview even has an article covering this with sample shots if you don't feel like doing the experiment yourself. It's incontrovertible fact, and it really does amaze me how many photographers refuse to grasp this concept. Usually it's 35mm photographers who had never shot any other formats before digital came along, and you'll hear them saying something like "I don't like DX format because I can't use a 60mm lens to get the same pleasing portrait perspective that my 85mm lens gave me on 35mm". Try shooting that 85mm portrait on 4x5" film and then tell me that it's the focal length that determines the perspective....
All this is true only if one ignores the definition of a wide-angle lens. In your example above where you write "crop the 17mm image so that it covers the same part of the scene as the 40mm image" you are in effect saying, 'turn the 17mm lens into an equivalent 40mm lens and it will behave like a 40mm lens'. This line of reasoning could be considered a tautology. The fact is a 40mm lens is not a wide angle lens on the 35mm format, neither on full frame nor on APS-C format. Any 17mm shot on a 35mm camera, of a scene at a specified distance will give one a different perspective of the scene than a 40mm shot of the same scene from the same distance, simply by virtue of the fact it is a different image with a wider field of view.
For example, in the 40mm shot there might be no visible background, no clues as to the closeness or relative size of the subject because all distant objects in the scene were not captured. I might be photographing, for example, a bas-relief on a small section of wall in a ruined temple. Using a 40mm lens, I might capture only the bas-relief and a bit of surrounding stone-work. In the 17mm shot, with lens pointing in the same direction, there will be vastly more 'picture information' surrounding the subject on all sides. There might be open fields in the background with small figures wandering around which will produce the effect that the bas-relief is huge and/or that one is very close to it. In this sense, the perspective of a 17mm shot is not the same as that of a 40mm lens at the same distance, on the same format of camera, as the eye sees it.
Whilst a 40mm lens is not a wide angle lens on the 35mm format, it is on full frame Medium Format. When we stitch images, we are in effect, increasing the format size of our camera, just as when we crop an image we are in effect increasing the focal length of our lens.
In my view, perspective is determined by both position and the focal length of the lens in relation to the camera format size.
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Any 17mm shot on a 35mm camera, of a scene at a specified distance will give one a different perspective of the scene than a 40mm shot of the same scene from the same distance, simply by virtue of the fact it is a different image with a wider field of view.
It must be a great fun to join to a discussion with a different understanding of the basic terminology than most others have.
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Excuse me, can anybody of you explain in simple words, possibly in one sentence, what the discussion is about? I see only random facts. The goal of the discussion is unclear to me. Sure its somehow about dof perspective and stitching, but the point of all of this got somehow out of sight.
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Excuse me, can anybody of you explain in simple words, possibly in one sentence, what the discussion is about? I see only random facts. The goal of the discussion is unclear to me. Sure its somehow about dof perspective and stitching, but the point of all of this got somehow out of sight.
I believe that the true underlying topic of this thread is the relationship between pink shrimps penis lenght and climate change in sub-tropical Russia. But I have been wrong before.
Cheers,
Bernard
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It must be a great fun to join to a discussion with a different understanding of the basic terminology than most others have.
My first digital camera was the cropped format D60 and I learned very quickly that a 50mm lens on that camera would produce not only the same perspective as an 80mm lens on full frame 35mm, from the same distance, but also the same FoV.
But I'm a bit uncomfortable with the notion that any lens from the same position, from 12mm to 600mm (if one were within the minimum focussing distance of the 600mm lens) would produce an image with the same perspective. They would be different images. If the 600mm shot included only a left nostril, then the 12mm shot might include the whole person in a large room.
If one were to compare A3 size prints of both images, it would seem a bit odd to me declare that the perspective of both images is the same, although I understand if the 12mm shot were sufficiently high resolution, and the 600mm shot were very low resolution, I could crop the 12mm shot and get a left nostril which looked very similar to the 600mm shot.
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But I'm a bit uncomfortable with the notion that any lens from the same position, from 12mm to 600mm (if one were within the minimum focussing distance of the 600mm lens) would produce an image with the same perspective. They would be different images.
They would be different crops but feature the same perspective, unless we all agree that the definition of the word perspective needs to be changed it might be wise to stick to its currently accepted definition.
Think of a world where some people use the word "pink shrimp" as meaning "great white shark" while others would use "great white shark" when they mean "corruption in sub-tropical Russia". Wouldn't that be confusing?
Cheers,
Bernard
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I believe that the true underlying topic of this thread is the relationship between pink shrimps penis lenght and climate change in sub-tropical Russia. But I have been wrong before.
Cheers,
Bernard
I meant it serious...
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They would be different crops but feature the same perspective, unless we all agree that the definition of the word perspective needs to be changed it might be wise to stick to its currently accepted definition.
Think of a world where some people use the word "pink shrimp" as meaning "great white shark" while others would use "great white shark" when they mean "corruption in sub-tropical Russia". Wouldn't that be confusing?
Cheers,
Bernard
Here's the Wikipedia definition of perspective.
"The two most characteristic features of perspective are that objects are drawn:
Smaller as their distance from the observer increases
Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight."
How can you compare the distance and size of objects in one image, taken with a wide-angle lens, with the distance and size of the same objects that don't exist in another image taken with a telephoto lens from the same position?
Size and distance are relative terms. 2mm is meaningful because it is twice the lenth of 1 mm and 1mm is a defined distance. An object is large in relation to another object that is smaller, but not large in relation to another object which is larger. If the smaller object doesn't exist in the image, because the image was taken with a long lens, then we have no sense of the size and distance of the larger object. The perspective in the two different images cannot therfore be the same.
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I meant it serious...
Well, the OP mentions two distinct subjects: DoF and perspective. DoF was not contested, but mixing perspective with FoV or framing is pretty regular.
I have not participated in the predecessor of this thread, but I think the underlying issue is, that some MFDB owners feel (IMO unnecessarily) to have to justify their decisions and spendings by a mystic quality of MFDB shots, namely the "3-D look". This quality is often mentioned but it has never been explained yet. I guess the "differerent perspective" of the very wide angle of view with large formats is supposed to substantiate the "3-D look".
In fact, the look of an image with wide ange is very different from others due to the different perspective, but the perspective difference is not caused by the lens itself but by the different position of the camera.
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Ray,
sometimes I have the feeling that you are being obtuse for the sake of obtuseness.
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In fact, the look of an image with wide ange is very different from others due to the different perspective, but the perspective difference is not caused by the lens itself but by the different position of the camera.
Can't you see a contradiction is that statement, Gabor? Are you saying that the look of an image with wide angle is only very different from others if the distance to subject is different?
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Ray,
sometimes I have the feeling that you are being obtuse for the sake of obtuseness.
Can't help that. I'm actually trying to reconcile two concepts here; the objective performance of the lens and the subjective impression of the viewer.
I would prefer a definition along the lines, 'Any lens used with any camera, from a given position, whatever the focal length and camera format, is potentially capable of delivering the same perspective in the image with either an appropriate amount of cropping, or an appropriate amount of stitching.'
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Can't you see a contradiction is that statement, Gabor? Are you saying that the look of an image with wide angle is only very different from others if the distance to subject is different?
There is no contradiction there. Like framing with different focal lengths can be achieved only from different positions, thus the second quoted sentence is meaningless regarding a single shot.
However, if stitching is acceptable, then one can create a compound image with the identical framing and identical perspective as the single, WA shot shows.
I would prefer a definition along the lines, 'Any lens used with any camera, from a given position, whatever the focal length and camera format, is potentially capable of delivering the same perspective in the image with either an appropriate amount of cropping, or an appropriate amount of stitching.'
This "definition" is a consequence of the actual definition of "perspective", thus there is no reason to include it in the definition.
Btw, watch out with "any lens"; this is true only re rectilinear lenses (although the warping by a stitcher can make a fisheye image rectilinear, but let's not go so far).
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This "definition" is a consequence of the actual definition of "perspective", thus there is no reason to include it in the definition.
Indeed it is, but I think the definition is necessary to exclude absurd situations. A definition that perspective has nothing to do with focal length, only distance to the subject, can lead one to either absurdities or situations that just appear incorrect to the viewer.
All definitions of 'perspective' that I've seen, refer to the relative sizes of objects in the scene according to distance. Here's one such definition, "the faculty of seeing all the relevant data in a meaningful relationship: Your data is admirably detailed but it lacks perspective."
I would maintain that a single shot with a 100mm lens may be admirably detailed, but could be perceived as lacking the perspective of a single shot from the same distance using a 24mm lens on the same camera. This is because the wider-angle shot includes more detail. That additional detail of recognisable and smaller objects in the background, and larger objects in the foreground, provides the visual clues as to perspective within the image.
Definitions should be able to stand on their own as being correct.
Btw, watch out with "any lens"; this is true only re rectilinear lenses (although the warping by a stitcher can make a fisheye image rectilinear, but let's not go so far).
Good point!
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Any 17mm shot on a 35mm camera, of a scene at a specified distance will give one a different perspective of the scene than a 40mm shot of the same scene from the same distance, simply by virtue of the fact it is a different image with a wider field of view.
You are intermingling the concepts of FOV and perspective. Nobody is disputing that a 17mm shot gives you a wider field of view. I'm not disputing the 17mm and 40mm images will be different, simply because the 40mm shot is a fairly small crop of the 17mm shot. In fact if you read my original post, I specifically said that the "wide angle effect" was a matter of perspective (camera location) and field of view:
Rectilinear distortion has everything to do with perspective and field of view. Note I said field of view, not focal length. Whether you get that perspective and field of view from a single wide-angle shot or by shooting several shots with a longer lens and then stitching them using a rectilinear projection, the resulting perspective will be the same.
And in fact, the whole point of the original question that started this thread, was whether you would get the same "wide-angle" effect of a single shot with a wide lens, by shooting the same scene with multiple shots from a longer lens and then stitchign them with pano software. My point was yes it's possible, because it's the camera position and field of view that matter, not the focal lenght. I stand by that statement, and Bernard even showed a real-world example that corroborates this.
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I meant it serious...
Sorry Christian, couldn't resist. Being serious is something I am simply not capable of in the world we live in... or is it solemn that I cannot be? http://www.ted.com/index.php/talks/paula_s...ts_serious.html (http://www.ted.com/index.php/talks/paula_scher_gets_serious.html)
Cheers,
Bernard
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I would maintain that a single shot with a 100mm lens may be admirably detailed, but could be perceived as lacking the perspective of a single shot from the same distance using a 24mm lens on the same camera. This is because the wider-angle shot includes more detail. That additional detail of recognisable and smaller objects in the background, and larger objects in the foreground, provides the visual clues as to perspective within the image.
Now, you're saying the exact opposite of what reality is. A 100mm lens will resolve more and therefore have more detail than a 24mm lens (assuming the quality of the lens are comparable). The 24mm lens will have a larger FOV than the 100mm, but equal sized FOV crops from either lens will have the same perspective and will only differ in the amount of detail and DOF. It doesn't matter if you're comparing single frames or stitched frames. The images posted earlier in this thread demonstrate this principal quite well.
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Now, you're saying the exact opposite of what reality is. A 100mm lens will resolve more and therefore have more detail than a 24mm lens ...
But that's more or less exactly what I said. This is what I wrote: "I would maintain that a single shot with a 100mm lens may be admirably detailed".
...equal sized FOV crops from either lens will have the same perspective and will only differ in the amount of detail and DOF.
Of course! That's a tautology. The same focal length of lens on the same format of camera will will produce an image of the same FoV (from the same distance) which will therefore have the same perspective. Detail will depend on sensor pixel density, and DoF will depend on F stop.
What I'm arguing against is the simplistic notion that perspective has nothing to do with focal length, period. Such a statement has to be qualified along the lines, 'provided the FoV of the resulting image is the same'. You can get that result by either cropping or stitching, depending on camera format. If you don't crop or stitch, then perspective is not just dependent upon distance to subject, but also on the focal length of lens used.
It needs to be mentioned.
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You are intermingling the concepts of FOV and perspective.
Yes I am, because I see them in all my images as being intermingled. Images with extensive FoV will tends to have greater, more obvious, more clearly defined perspective.
Lenses with a short focal length tend to have a wide FoV, and used from the same distance as a longer focal length, will tend to produce a greater perspective than the longer lens, as a result of their wider FoV.
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Yes I am, because I see them in all my images as being intermingled. Images with extensive FoV will tends to have greater, more obvious, more clearly defined perspective.
Lenses with a short focal length tend to have a wide FoV, and used from the same distance as a longer focal length, will tend to produce a greater perspective than the longer lens, as a result of their wider FoV.
This is just silly, how do you explain the images in post #23 of this thread. When stitching is involved there is no defined FOV for a particular focal length. The FOV will be whatever you want it to be. Your definition of perspective is not the commonly accepted definition.
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What I'm arguing against is the simplistic notion that perspective has nothing to do with focal length, period. Such a statement has to be qualified along the lines, 'provided the FoV of the resulting image is the same'.
Ray,
I again (still?) have the feeling that you are being obtuse for the sake of obtuseness. You must be bored.
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Members who only wish to read constructive comments...
...you can set your profile to ignore named users, so that their posts do not appear on your computer... you just get a message asking you if you want to "Un-ignore" them.
I suggest the the word "perspective" should not be used without qualification. e.g. "view point perspective".
The phrase "focal length " should only be used in relation to a specific format, and if you are writing about Field Of View (angle) then use the term FOV, (with a specified angle if required).
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Lenses with a short focal length tend to have a wide FoV, and used from the same distance as a longer focal length, will tend to produce a greater perspective than the longer lens, as a result of their wider FoV.
This is incorrect. From the same distance/position a wider lens will have a wider FoV but will have the same perspective as a longer lens.
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This is incorrect. From the same distance/position a wider lens will have a wider FoV but will have the same perspective as a longer lens.
That is my understanding too. Perspective is a function of distance only. A wide lens allows you to get closer for a given subject framing and hence increase perspective.
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From the same distance/position a wider lens will have a wider FoV but will have the same perspective as a longer lens.
Perspective = viewpoint... same viewpoint, same (viewpoint) perspective.
Zero = infinity!
You can achieve zero perspective by shooting from infinity...
You can achieve near-zero perspective by shooting from a viewpoint where the subject distance is very great compared to the format size... i.e. by using a small Field Of View. (The moon seems to have little perspective, viewed from the UK.)
...or you can create a virtual view point at infinity by changing your actual viewpoint for every column of pixels (or pan-and-stitch shot). Mount a Seitz scan back sensor on a rail or lazar beam so that, for every row of pixels, the light reaching the sensor travels perpendicularly to the (near co-planar) subject surface (and the sensor), and you can achieve zero perspective. (I do not think they have invented the kit for this yet, but they have invented a lazar-guided system for painting white lines on football fields, and this system could be adapted)
Co-planar (flat) subjects (like a painting) are perspective-free, anyway, if your sensor is parallel to the subject... but, with a view camera you can achieve this with the camera offset, e.g. to avoid obstacles or to avoid seeing the reflection of the camera in glass.
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Well, the OP mentions two distinct subjects: DoF and perspective. DoF was not contested, but mixing perspective with FoV or framing is pretty regular.
I have not participated in the predecessor of this thread, but I think the underlying issue is, that some MFDB owners feel (IMO unnecessarily) to have to justify their decisions and spendings by a mystic quality of MFDB shots, namely the "3-D look". This quality is often mentioned but it has never been explained yet. I guess the "differerent perspective" of the very wide angle of view with large formats is supposed to substantiate the "3-D look".
In fact, the look of an image with wide ange is very different from others due to the different perspective, but the perspective difference is not caused by the lens itself but by the different position of the camera.
Sorry Christian, couldn't resist. Being serious is something I am simply not capable of in the world we live in... or is it solemn that I cannot be? http://www.ted.com/index.php/talks/paula_s...ts_serious.html (http://www.ted.com/index.php/talks/paula_scher_gets_serious.html)
Cheers,
Bernard
Gabor, Bernard,
(Bernarnd the video is actually a very brilliant one and yes I understand you I too cannot be completely serious in this world, far from it, and your remark gave me a good chuckle However in such heated (??) discussions I almost never joke just to prevent misunderstandings.)
(Gabor the 3D look is for me how defined pixels are. Of course that cannot be real 3d but I think one can be just more inspired by looking at sharper samples out of cam and call this 3d look instead of the a bit more mushy stuff out of 35mm. 3d look is in my eyes a way of putting: mfdb source images are just sharper. It also mirrors the joy and fascination of owning such a high-end device. Not wanting to start THIS discussion, just mentioning my way to understand the term because I think the term is absolutely valid in this regard in my eyes. I also personally would 3d look being a misconception not rub under the nose of people it gives only heat.)
I now feel my question what this thread is about wich was intended to somehow "sort" the discussion isnt worth the hassle. I re-read portions of this and the last closed thread. My observation: All questions have been answered, there is a lot of knowledge but unfortunately also a lot of misunderstandings.
My conclusion is, it is perfectly possible to achieve with a lower camera through stitching exactly the same results as a higher quality system regarding
a: pixel sharness: Because oversampling through stitching and downrezzing compensates lower quality look of 35mm
b: perspective: Because perspective has to do only with my own position in space.
There are of course up- and downsides to mfdb and 35mm. At the end it all depends on what one wants to do and there is no single ideal way. This is boringly common, but in my eyes very important. These discussions degenerate because we fail to see the different perspective of others and that indeed also someone can be happy with a solution wich would not be mine at all. And sometimes if I see I cannot convice the other of my view I just leave him alone. Saves my nerves.
Cheers,
Christian
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it seems from here in Switzerland too, I have been having this feeling yesterday night.
Thierry
... (The moon seems to have little perspective, viewed from the UK.) ...
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Seen from the Netherlands, the moon has even less perspective than from Switzerland, which is a few feet nearer to the moon
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This is just silly, how do you explain the images in post #23 of this thread. When stitching is involved there is no defined FOV for a particular focal length. The FOV will be whatever you want it to be. Your definition of perspective is not the commonly accepted definition.
How do I explain the images in post #23? They were all taken with the same effective focal length of lens. The images taken with the shorter focal lengths were cropped to the same FoV as the longest focal length. I accept that cropping an image from any lens effectively increases the focal length of the lens.
What happens if you don't crop the image taken with the shorter focal length? Here are two pairs of images below. Each pair of images was taken with the same physical lens, same camera, same position, same time. You could consider the cropped image as the first of a series of shots taken with an effectively longer focal length lens for stitching purposes.
If you consider that FoV has no bearing on perspective, then you would presumably consider that both images in each pair below have the same perspective. Is this correct?
[attachment=16433:Angkor_c...rop_7526.jpg] [attachment=16434:Angkor_c...dor_7526.jpg]
[attachment=16435:4463_crop.jpg] [attachment=16436:4463.jpg]
Your definition of perspective is not the commonly accepted definition.
I'm using the Wikipedia definition as follows:
The two most characteristic features of perspective are that objects appear, (1)Smaller as their distance from the observer increases. (2)Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight.
What definition are you using?
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How do I explain the images in post #23? They were all taken with the same effective focal length of lens. The images taken with the shorter focal lengths were cropped to the same FoV as the longest focal length. I accept that cropping an image from any lens effectively increases the focal length of the lens.
What happens if you don't crop the image taken with the shorter focal length? Here are two pairs of images below. Each pair of images was taken with the same physical lens, same camera, same position, same time. You could consider the cropped image as the first of a series of shots taken with an effectively longer focal length lens for stitching purposes.
You can't compare if you don't crop, as simple as that, but the perspective of all images taken with different focal length lenses and from the same distance/angle IS the very SAME: again, perspective is about converging or diverging lines, not size or reproduction scale.
Now I do accept that such images produce a different visual effect, impression or feeling.
If you consider that FoV has no bearing on perspective, then you would presumably consider that both images in each pair below have the same perspective. Is this correct?
"Strangely" they do! And without any doubt.
I'm using the Wikipedia definition as follows:
The two most characteristic features of perspective are that objects appear, (1)Smaller as their distance from the observer increases. (2)Foreshortened: the size of an object's dimensions along the line of sight are relatively shorter than dimensions across the line of sight.
The definition of perspective is NOT the size/reproduction ratio of the subject or object photographed, but solely the converging and diverging lines/forms in this reproduction. I am sorry to say that Wikipedia or not, that is a wrong definition.
Ray, I think we all understand your point, but as said by someone else, the perspective has been explained, understood and defined as such and cannot be changed: it is SOLELY the distance/angle of shooting having an influence, nothing else
Best regards,
Thierry
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Here is a guy who posted some pretty good examples using the same lenses at differing distances and different lenses at the same distance with comparative crops:
http://jamesmskipper.tripod.com/jamesmskip...erspective.html (http://jamesmskipper.tripod.com/jamesmskipper/photo_perspective.html)
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You can't compare if you don't crop, as simple as that, but the perspective of all images taken with different focal length lenses and from the same distance/angle IS the very SAME: again, perspective is about converging or diverging lines, not size or reproduction scale.
Now I do accept that such images produce a different visual effect, impression or feeling.
"Strangely" they do! And without any doubt.
The definition of perspective is NOT the size/reproduction ratio of the subject or object photographed, but solely the converging and diverging lines/forms in this reproduction. I am sorry to say that Wikipedia or not, that is a wrong definition.
Ray, I think we all understand your point, but as said by someone else, the perspective has been explained, understood and defined as such and cannot be changed: it is SOLELY the distance/angle of shooting having an influence, nothing else
Best regards,
Thierry
Excellent description. I can only add that FOV is not really relevant when stitching. The photographer chooses the FOV of the image by the number of images he or she takes and it isn't constrained by the focal length of the lens. A wide angle lens and a telephoto lens can have the same FOV in a stitched image, but one will have a higher resolution.
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I suggest a new term of photography, rayspective, the combination of FoV and perspective. Two rectilinear images are rayspectively identical, if they have the same FoV, the same perspective and are viewed in the same size (on paper or monitor), and, of course, if they depict the same scenery.
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I suggest a new term of photography, rayspective, the combination of FoV and perspective. Two rectilinear images are rayspectively identical, if they have the same FoV, the same perspective and are viewed in the same size (on paper or monitor), and, of course, if they depict the same scenery.
Now that was funny!
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You can't compare if you don't crop, as simple as that....
Precisely! This is one of the problems I have with the proof that all lenses produce the same perspective from the same distance to subject. When you crop a scene taken with a shorter lens in order to demonstrate that it has the same perspective as the image taken with the longer lens, you are effectively comparing images taken with the same focal length of lens.
It's like saying, "All lenses whatever their focal length produce the same perspective. I will now proceed to prove this point by comparing two images taken with effectively the same focal length of lens." What sort of proof is that? As I mentioned before, this is a mere tautology.
If you consider that FoV has no bearing on perspective, then you would presumably consider that both images in each pair below have the same perspective. Is this correct?
[attachment=16435:4463_crop.jpg] [attachment=16436:4463.jpg]
"Strangely" they do! And without any doubt.
How did you work that out? You didn't by any chance enlarge/crop on the monitor the small figure in the full scene till it was the same size as my crop in the first image above, did you; thus effectively equalising the focal length of the lenses for comparison purposes?
Supposing I were to make large, equal-size prints of the two images above. Would it be immediately apparent that the small figure in the lower part of the full scene (taken with a 24mm lens) had the same perspective as the blown-up crop next to it, effectively taken with a 150mm lens? Or would you have to change your perspective when viewing both prints in order to determine that the perspective is the same? That is, would you have to view the print of the full scene from a distance of say 10", examine the background and the relative size of the foliage in the background, fix that impression in your mind, then walk back a few steps?
I think that might be more difficult than effectively equalising the focal length of the lenses by cropping the full image on the monitor to the same FoV and size as my enlargement of the crop above, thus proving that, when two images are made equal, then it logically follows that they are equal.
The definition of perspective is NOT the size/reproduction ratio of the subject or object photographed, but solely the converging and diverging lines/forms in this reproduction. I am sorry to say that Wikipedia or not, that is a wrong definition.
What! You mean it is not true that a chief characteristic of perspective is that objects appear smaller the greater their distance from the viewer? I never realised that! Jeez! I really must have a distorted sense of perspective.
perspective ......... is SOLELY the distance/angle of shooting having an influence, nothing else
Distance/angle? Isn't angle related to FoV and focal length?
Now I do accept that such images produce a different visual effect, impression or feeling.
But you are quite sure that the different visual effect, impression or feeling produced by the wide-angle lens has nothing to do with perspective.
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Precisely! This is one of the problems I have with the proof that all lenses produce the same perspective from the same distance to subject. When you crop a scene taken with a shorter lens in order to demonstrate that it has the same perspective as the image taken with the longer lens, you are effectively comparing images taken with the same focal length of lens.
It's like saying, "All lenses whatever their focal length produce the same perspective. I will now proceed to prove this point by comparing two images taken with effectively the same focal length of lens." What sort of proof is that? As I mentioned before, this is a mere tautology.
How did you work that out? You didn't by any chance enlarge/crop on the monitor the small figure in the full scene till it was the same size as my crop in the first image above, did you; thus effectively equalising the focal length of the lenses for comparison purposes?
Supposing I were to make large, equal-size prints of the two images above. Would it be immediately apparent that the small figure in the lower part of the full scene (taken with a 24mm lens) had the same perspective as the blown-up crop next to it, effectively taken with a 150mm lens? Or would you have to change your perspective when viewing both prints in order to determine that the perspective is the same? That is, would you have to view the print of the full scene from a distance of say 10", examine the background and the relative size of the foliage in the background, fix that impression in your mind, then walk back a few steps?
I think that might be more difficult than effectively equalising the focal length of the lenses by cropping the full image on the monitor to the same FoV and size as my enlargement of the crop above, thus proving that, when two images are made equal, then it logically follows that they are equal.
What! You mean it is not true that a chief characteristic of perspective is that objects appear smaller the greater their distance from the viewer? I never realised that! Jeez! I really must have a distorted sense of perspective.
Distance/angle? Isn't angle related to FoV and focal length?
But you are quite sure that the different visual effect, impression or feeling produced by the wide-angle lens has nothing to do with perspective.
Which of these statements are true?
1. If any portion of two images are identical, then all portions of both images will be identical when those portions are included in the field of view.
2. Focal length of a lens is unrelated to the perspective of an image.
3. Format size of the camera (film or sensor) has no effect on the perspective.
4. Stitched images can have any FOV, including greater than 360 degrees.
5. Perspective is only determined by camera position relative to the subject.
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Which of these statements are true?
1. If any portion of two images are identical, then all portions of both images will be identical when those portions are included in the field of view.
2. Focal length of a lens is unrelated to the perspective of an image.
3. Format size of the camera (film or sensor) has no effect on the perspective.
4. Stitched images can have any FOV, including greater than 360 degrees.
5. Perspective is only determined by camera position relative to the subject.
1, 2, 3, 5
(but something tells me that this is trick question and 4 is somehow true??)
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Which of these statements are true?
1. If any portion of two images are identical, then all portions of both images will be identical when those portions are included in the field of view.
Only true when both images are taken with the same focal length of lens. If one of the two images is taken with a wider-angle lens it will include portions which cannot be included in the other image. If you arrange things so that both images contain the same portions, they are essentially the same images taken with effectively the same FL of lens. Then, of course perspective will be the same.
2. Focal length of a lens is unrelated to the perspective of an image
.
Only true if one excludes the perspective of the person viewing the image.
3. Format size of the camera (film or sensor) has no effect on the perspective.
Depends on the lens used. It may or may not. The sensor without lens makes some very strange images.
4. Stitched images can have any FOV, including greater than 360 degrees.
I would say this is not true.
5. Perspective is only determined by camera position relative to the subject.
Which subject? For the statement to be meaningful you have to specify the subject, so I'll rephrase this statement for you. 5. Perspective is only determined by camera position in relation to a specified subject.
The focal length of the lens, and direction pointed, specifies the subject. Change the focal length of the lens, without changing your position, then you change the nature of the subject. You've shifted the goal posts and all bets are off
In conclusion, none of your statements are completely true.
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(but something tells me that this is trick question and 4 is somehow true??)
Not the question, but the pano is a trick. I have seen such; someone shot the frames with enough delay, that when the camera reached the starting position, the daylight scenery become late evening and then night; thus the shots covered more than 360° and the changing illumination made the impression of different scenery.
This is the only kind of pano over 360° I know of. Of course, the scenery can change on different ways, not only through time delay.
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1. If any portion of two images are identical, then all portions of both images will be identical when those portions are included in the field of view.
Only true when both images are taken with the same focal length of lens. If one of the two images is taken with a wider-angle lens it will include portions which cannot be included in the other image. If you arrange things so that both images contain the same portions, they are essentially the same images taken with effectively the same FL of lens. Then, of course perspective will be the same.
A single frame of the stitched image will have different FOV when different focal length lens are used. The FOV of a stitched image can be the same for any focal length and (here's the part you don't seem to believe) the perspective will be the same.
.
2. Focal length of a lens is unrelated to the perspective of an image
.
Only true if one excludes the perspective of the person viewing the image.
How does a person have perspective?
3. Format size of the camera (film or sensor) has no effect on the perspective.
Depends on the lens used. It may or may not. The sensor without lens makes some very strange images.
The lens has no knowlege of the sensor, it cannot change the light passing through it based on a sensor located behind it. The only thing that changes is the FOV. Some sensors will be able to resolve more, but they can't change the perspective.
4. Stitched images can have any FOV, including greater than 360 degrees.
I would say this is not true.
Actually it is. When stitching images you can continue around and around. Pano heads don't have stops at 360 degrees.
5. Perspective is only determined by camera position relative to the subject.
Which subject? For the statement to be meaningful you have to specify the subject, so I'll rephrase this statement for you. 5. Perspective is only determined by camera position in relation to a specified subject.
The subject can be everything in the image. It is correct as originally stated. (Actually, your rephrasing didn't change anything)
The focal length of the lens, and direction pointed, specifies the subject. Change the focal length of the lens, without changing your position, then you change the nature of the subject. You've shifted the goal posts and all bets are off
Sorry, your analysis is just not true. I think the only way you will be able to realize this is to stitch several images together yourself. I'd suggest using a 35mm and 70mm. Make a 2 image wide stitch with the 35mm and a 4x4 stitch with the 70mm (very minor cropping allowed to make each have the same FOV). For bonus points, how will you be able to determine which image was shot with which lens or to put it another way what focal length will you say the stitched image used since the FOV is the same?
In conclusion, none of your statements are completely true.
Actually they're all true
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Now I am shocked that some dear colleagues in this forum could not understand perspective even they could have posted hundreds or thousands times. I recall I learned this basic theory of Optics in middle school, unfortunately, I really did not expect so much effort were needed to explain this term.
[attachment=16464:focus.jpg]
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That's exactly what I have said to another colleague, even with kinder terms and words, and I have been accused of insulting him: be careful!
Thierry
Now I am shocked that some dear colleagues in this forum could not understand perspective even they could have posted hundreds or thousands times. I recall I learned this basic theory of Optics in middle school, unfortunately, I really did not expect so much effort were needed to explain this term.
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Now I am shocked that some dear colleagues in this forum could not understand perspective even they could have posted hundreds or thousands times. I recall I learned this basic theory of Optics in middle school
I am shocked that you are mixing up the projection of a single point (or of a line segment) with perspective. Perspective is the relationship between several projected points of objects (this includes lines, etc.).
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I am shocked that you are mixing up the projection of a single point (or of a line segment) with perspective. Perspective is the relationship between several projected points of objects (this includes lines, etc.).
Yes, go ahead to follow the theory and figure out how "several projected points of objects" are projected, you will find out what "perspective" means.
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More examples: http://www.phototakers.com/forum/ftopic36480.html (http://www.phototakers.com/forum/ftopic36480.html)
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Dear Ray,
I think what you are referring to is the common experience we share when using different focal lenghts. This experience of course stays the same no matter how we explain it in the end. We look at a wideangle image and say: Wow, now thats a nice perspective! And we mean the whole impression, we dont analyze it. In reality this is incorrect formulated, we should say, what a nice perspective and angle of view! Of course nobody does this! What GIVES this view, IS the perspective, is MY perspective, the point I am standing. The other part is my angle of view.
A good way to think about perspective is to think about objects occluding other objects. When you dont move your head, of course everything remains static. If you move your head around, the occlusion of objects, the direction of lines, etc, change. The actual scenery remains as it is, only your position in space changes. Its my perspective, the point where I look from, my standpoint. If I take a steelplate with a square in it and look through it, that doesnt change perspective. Also a lens at different focal lenghts and same position doesnt change anything about the occlusion of objects. Sure, I might see more things around, the same "crop" is smaller or larger, but the only difference is that I see more around. Likewise, If you dont move your head but focus your attention only at a small thing wide away, and then at the whole scene, nothing changes except your conciousness. And so you could view differnet focal lenghts just as optimized projectors for different attention-angles (funny term but only for the sake of the analogy), that is different view angles.
So yes if you are refering to our common sense - we tend to totally neglect our own effect (walking around!) on perspective and only see what different lenses do - then yes, in common sense, a wideangle gives "a nice perspective", but if we take that apart and really try to understand HOW it works, we need to rethink some of our common phrases, and eventually come to realize that it works somehow different then common sense suggests. And yes, if you where saying different lenses give different viewing experiences (after all, we have them for a reason) if you refer to THAT well there is no dispute that this is correct.
To end here, I read your last posts and tried to understand how you where thinking about it, I hope this makes somehow sense to you.
Christian
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A good way to think about perspective is to think about objects occluding other objects. When you dont move your head, of course everything remains static. If you move your head around, the occlusion of objects, the direction of lines, etc, change.
Christian
This is parallax, which may not, technically be "converging lines" perspective!
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A single frame of the stitched image will have different FOV when different focal length lens are used. The FOV of a stitched image can be the same for any focal length and (here's the part you don't seem to believe) the perspective will be the same.
Of course I believe it. Any image of the same FoV taken from the same position, and taken with any lens on any format of camera will have the same perspective.
The only point I am making is that FoV is related to effective focal length. If the FoV of two images is different, despite the fact that both images have been shot from the same position, then the subject matter is different, the focal length of lens used is different and therefore the perspective is different because perspective has to relate to a specific subject. Or perhaps you would like to argue that the perspective of a non-existent subject can be the same as the perspective of an existing subject.
How does a person have perspective?
A person viewing a photographic image must view it from a specific position and that position will influence the sense of perspective in the image, as experienced by the viewer, but will not soley determine perspective. The image itself has its own perspective determined by the relative size of all identifiable objects within the composition.
In my examples above, from Angkor Wat, which show a pair of images of the same size, but the first one a small crop of the other, the size of the images (or prints) affects the experience of perspective in the viewer. Large prints can be appreciated from a greater distance than small prints.
Thierry has claimed that the perspective of my enlarged crop is the same as that portion of the image in the full scene from which the crop was made. Well, of course it is. Two equal images are equal.
The interesting question is, how would anyone who didn't know beforehand that one image was an enlarged crop of the wider FoV image, be able to discern that the cropped image, of equal size to the whole image from which the crop was taken, be able to discern that the perspective was the same?
My assertion is, they wouldn't be able to unless they effectively altered their own subjective perspective of the full scene, by examining it up close, and making the the same visual crop in their mind that I had made in Photoshop, then retreating to compare it with the other image.
Sorry, your analysis is just not true. I think the only way you will be able to realize this is to stitch several images together yourself.
The first image I ever sold was a 13 image stitch from 35mm film about 15 years ago. Sold it to the local City Council. I'm very much in favour of the practice of stitching. I'm pleased that stitching programs continue to improve. I really do understand that you can use any lens for stitching and get the same perspective in the same scene. I'm just uncomfortable with the statement that you can get the same perspective in two different scenes, or whatever the scene.
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We look forward to
I have started a thread to compare the P65+ to the H3D11-60.
In the mean time, one example of a handheld 300mm image.
http://www.flickr.com/photos/bernardlangui...647680/sizes/o/ (http://www.flickr.com/photos/bernardlanguillier/3900647680/sizes/o/)
I find it to be just as sharp as the P65+ 100% crop samples just posted at outbackphoto, but I guess you will tell me than they messed up...
Cheers,
Bernard
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More examples: http://www.phototakers.com/forum/ftopic36480.html (http://www.phototakers.com/forum/ftopic36480.html)
These are not "more examples" but "examples". The drawing of the projection of a single point is neither an example for nor a demonstration of "perspective".
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This is parallax, which may not, technically be "converging lines" perspective!
And parallax is part and parcel to perspective since it dictates how 3D objects will appear relationally when rendered in 2D...
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In the mean time, one example of a handheld 300mm image.
http://www.flickr.com/photos/bernardlangui...647680/sizes/o/ (http://www.flickr.com/photos/bernardlanguillier/3900647680/sizes/o/)
I find it to be just as sharp as the P65+ 100% crop samples just posted at outbackphoto, but I guess you will tell me than they messed up...
Cheers,
Bernard
Resolution maybe, DR no...
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I find it to be just as sharp as the P65+ 100% crop samples just posted at outbackphoto, but I guess you will tell me than they messed up...
yes
f22 and f18 are certainly not the apertures to show the P65+ files at the best
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In my examples above, from Angkor Wat, which show a pair of images of the same size, but the first one a small crop of the other, the size of the images (or prints) affects the experience of perspective in the viewer. Large prints can be appreciated from a greater distance than small prints.
...
The interesting question is, how would anyone who didn't know beforehand that one image was an enlarged crop of the wider FoV image, be able to discern that the cropped image, of equal size to the whole image from which the crop was taken, be able to discern that the perspective was the same?
Ray, honestly, the entertaining value of the faked lack of understanding of the basics is wearing off.
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I find it to be just as sharp as the P65+ 100% crop samples just posted at outbackphoto, but I guess you will tell me than they messed up...
Cheers,
Bernard
Looks OK, Bernard... but pictures look sharp if the kit can resolve the detail in the picture... not all pictures have detail that cannot be seen in a hand-held 300mm shot taken with a Small DSLR with an anti-aliasing filter.
It a good example of a shot for which pan-and-stitch is not suitable!
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This is parallax, which may not, technically be "converging lines" perspective!
Sure. I could have said this for myself. But I think its still clear what I wanted to say
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I find it to be just as sharp as the P65+ 100% crop samples just posted at outbackphoto, but I guess you will tell me than they messed up...
+1 Tho_Mas comment that the P65+ does not sing at f/22 as used in the Outback Photo article. See this test (http://www.captureintegration.com/tests/phase-one/) for an example of 100% pixel sharpness at varying f-stops with a P65+ using Phase One glass. Bare in mind that the f/22 shot will still make an impressive print, but for maximum detail it is not the best f-stop.
+1 the incredible dynamic range / virtually non-present noise of the 65+ are important to bare in mind when you're getting too far into pure-resolution discussions. You'll enjoy these when you rent the 65+ soon.
Doug Peterson ()
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+1 Tho_Mas comment that the P65+ does not sing at f/22 as used in the Outback Photo article. See this test (http://www.captureintegration.com/tests/phase-one/) for an example of 100% pixel sharpness at varying f-stops with a P65+ using Phase One glass. Bare in mind that the f/22 shot will still make an impressive print, but for maximum detail it is not the best f-stop.
+1 the incredible dynamic range / virtually non-present noise of the 65+ are important to bare in mind when you're getting too far into pure-resolution discussions. You'll enjoy these when you rent the 65+ soon.
Looking at DxO Mark comparison of D3x vs P65+ (http://www.dxomark.com/index.php/eng/Image-Quality-Database/Compare-cameras/%28appareil1%29/287|0/%28appareil2%29/318|0/%28onglet%29/0/%28brand%29/Nikon/%28brand2%29/Phase%20One) paints a difference story. Setting aside high-ISO performance and pixel count, these two sensors are actually pretty similar in performance. The P65+ has a slight edge in some categories, but not others (including Dynamic Range - where the D3x comes out on top, probably due to cleaner shadows). DxOMark doesn't measure/score on resolution, and the MFDB will have an advantage there, even at the pixel level due to not having an AA filter. But if you apply the appropriate capture sharpening to the D3x shot and compare at the pixel level, it's not going to be the huge night and day difference that some MF proponents would have us believe.
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It a good example of a shot for which pan-and-stitch is not suitable!
True, but also a good example of a locale/subject where a back is of little use... I don't believe that many humans have the physical ability to climb there with a 500mm Mamiya lens together with a pro level anti-vibration gyro device...
Cheers,
Bernard
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Resolution maybe, DR no...
How can you tell? I have significantly increased the contrast of this image because that is how I think it looks good.
Shadows are totally clean and could be pushed a lot. Of course you'd have to do it before sharpening for best results.
Cheers,
Bernard
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The only point I am making is that FoV is related to effective focal length. If the FoV of two images is different, despite the fact that both images have been shot from the same position, then the subject matter is different, the focal length of lens used is different and therefore the perspective is different.
Sorry Ray, this is quite incorrect.
Focal length, FoV have absolutely nothing to do with perspective or parallax. The relationship between objects in any scene is fixed when viewed from a single point. Change the viewpoint and the perspective, parallax, whatever, changes but only if you move the point.
Remember that focal length and FoV are not the only two variables here, and are only loosely connected. FoV depends on the sensor size and image circle of the lens design. Focal length is, at it's simplest, just a measure of the distance from the lens centre to sensor plane when the lens focuses at infinity. A 100mm lens on a large film/sensor (10x8) is a wide angle. A 100mm lens on a GH1 is a telephoto. How then can changing the sensor (by changing cameras) affect the perspective?
http://jamesmskipper.tripod.com/jamesmskip...erspective.html (http://jamesmskipper.tripod.com/jamesmskipper/photo_perspective.html)
These images make the point clearly.
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How can you tell? I have significantly increased the contrast of this image because that is how I think it looks good.
I know because I've shot both and worked extensively with the files. And anybody else that has worked extensively with both will tell you the same thing...
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I know because I've shot both and worked extensively with the files. And anybody else that has worked extensively with both will tell you the same thing...
OK, fair comment. I assume that you used C1 Pro to convert both these files? Did you do side to side comparisons?
If it is the case, that might save me 800 US$ if these were available.
Thanks.
Cheers,
Bernard
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Ray, honestly, the entertaining value of the faked lack of understanding of the basics is wearing off.
I often find that disputes about issues result from the issues not being clearly defined in the first instance, so people can find themselves actually arguing about different things although they might think they are arguing about the same thing.
How about the following definition.
As a theoretical construct and property of lenses, unrelated to the making of a picture or composition and therfore excluding the perspective of a potential viewer, the theroetical perspective through the lens is independent of its focal length or the format of the camera it is attached to, and is determined only by the distance between the lens and the theoretical subject.
However, when creating a photographic composition, which most photographers try to do now and again, the focal length of the lens and the format size of the camera will both influence the distance to the subject(s), the size of the subject within the composition and the number of individual subjects or objects within the composition at varying distances from the photographer.
How's that as a piece of clarity?
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How about the following definition.
- It is not a definition but an explanation.
- It relies on your incorrect interpretation of perspective (it is circular).
- How about sticking to the existing, working meaning of perspective? You are free to use rayspective to your purposes (or devise another, new term for that), but I don't think that photographers will change their correct interpretation of a customary term for your sake.
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So yes if you are refering to our common sense - we tend to totally neglect our own effect (walking around!) on perspective and only see what different lenses do - then yes, in common sense, a wideangle gives "a nice perspective", but if we take that apart and really try to understand HOW it works, we need to rethink some of our common phrases, and eventually come to realize that it works somehow different then common sense suggests. And yes, if you where saying different lenses give different viewing experiences (after all, we have them for a reason) if you refer to THAT well there is no dispute that this is correct.
To end here, I read your last posts and tried to understand how you where thinking about it, I hope this makes somehow sense to you.
Christian,
Regardless of whether a wide-angle lens produces a nice perspective or a horrible perspective, it produces a different image to that produced by a longer lens (from the same position) and the objects in that different image will relate in a way which produces a changed perspective of the viewer, will they not?
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...
As a theoretical construct and property of lenses, unrelated to the making of a picture or composition and therfore excluding the perspective of a potential viewer, the theroetical perspective through the lens is independent of its focal length or the format of the camera it is attached to, and is determined only by the distance between the lens and the theoretical subject.
However, when creating a photographic composition, which most photographers try to do now and again, the focal length of the lens and the format size of the camera will both influence the distance to the subject(s), the size of the subject within the composition and the number of individual subjects or objects within the composition at varying distances from the photographer.
...
Ok, written a bit complicated, but I translate this basically to:
===
In theory, perspective is independent of focal lenght.
But as soon as someone says "a tele optic compresses and a wide optic exaggerates perspective" wich everybody does, the meaning of perspective becomes different and now involves also the field of view of a lens. (As addition to only the position.)
===
IF we where to insist on using **only** the correct definition of perspective, we could rephrase it as:
To achieve roughly the same framing for a wide and a tele optic, one has to move the tele optic farther away because of its narrower angle of view. As a result the perspective changes. The same view wich occupied a big angle of view from near disctance now occupies a small angle of view and due to this the also perspective differs.
The common speech has shortened this, dont mention the movement because it is implicit (you always have to do it) and instead just takes the focal lenght (wich in play with the sensor size results in a angle of view) as a synonym for the impression that will result, and calls this perspective.
So essentially the abbreviation "a tele optic compresses and a wide optic exaggerates perspective" centers about the practial consequences and dont care about the correct definition. One half is the scientifically correct definition, the other half is the practical consequence. Both can't be neglected. Both are valid in their context, else they wouldnt exist.
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Christian,
Regardless of whether a wide-angle lens produces a nice perspective or a horrible perspective, it produces a different image to that produced by a longer lens (from the same position) and the objects in that different image will relate in a way which produces a changed perspective of the viewer, will they not?
Ray, I now see this answer of yours after I have written my other posting just above this one. I would essentially write a similar explanation here so please take my other (first) answer also as an answer to this. (Basically I would agree partly that for practial purposes the images ARE different, but the perspective... oh well, and there I am at my last post )
Cheers,
Christian
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To achieve roughly the same framing for a wide and a tele optic, one has to move the tele optic farther away because of its narrower angle of view. As a result the perspective changes. The same view wich occupied a big angle of view from near distance now occupies a small angle of view and due to this the also perspective differs.
Agreed! But I get the impression there's something else happening with ultra-wide-angle shots which are wider than the normal FoV of human vision. The wide-angle photographic image allows the eye and brain to capture in one glance, perspective detail which in the real world would be impossible. Whilst the FoV of the human eye is quite wide, if one includes periphery vision which is good for detecting movement but hopleless for discerning detail, the actual FoV of focussed human vision is quite narrow. I never get a sense in the real world, when examining detail from a close distance, of the apparent perspective distortion one finds in a wide-angle photographic image.
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Agreed! But I get the impression there's something else happening with ultra-wide-angle shots which are wider than the normal FoV of human vision. The wide-angle photographic image allows the eye and brain to capture in one glance, perspective detail which in the real world would be impossible. Whilst the FoV of the human eye is quite wide, if one includes periphery vision which is good for detecting movement but hopleless for discerning detail, the actual FoV of focussed human vision is quite narrow. I never get a sense in the real world, when examining detail from a close distance, of the apparent perspective distortion one finds in a wide-angle photographic image.
All this can still be explained by the basic priciples of optics and physics...
your eye is a lens too...
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All this can still be explained by the basic priciples of optics and physics...
your eye is a lens too...
But the brain has to interpret everything that is seen. I don't believe for example, when you stand one foot away from a person, that his/her features appear as distorted as they would in a wide-angle photo taken from the same distance. I mean, if you are standing close to someone in a lift for example, you don't exclaim (or even think), "Oh! You do look funny!" However, if you were to take a photo of that person from the same distance, using say a 14mm lens on a DSLR, the photo could be quite amusing.
Is this effect explained by optics or by the way the brain interprets the unusual perspective in a image provided by the additional objects that only a wide-angle lens can capture?
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OK, fair comment. I assume that you used C1 Pro to convert both these files? Did you do side to side comparisons?
If it is the case, that might save me 800 US$ if these were available.
Thanks.
Cheers,
Bernard
C1 pro yes, as it is my preferred converter. Side-by-sides not exactly. Similar shots in similar conditions, not scientifically controlled but literally thousands of frames -- more than enough that I am certain . I'll share this little verbal example with you though: When we had our workshop in Moab this past winter, myself and two assistants were shooting a late landscape with the sun setting behind us. Here the sky was still light but the foreground was dark in shadow, just the tips of the mittens still lit. One assistant and myself were shooting our MF outfits (P45+) and the other assistant was shooting his 5D2. We -- the P45= shooters -- were shooting single frames as we had all week, easily capturing the entire range of tonality. However, the 5D2 shooter was now shooting doubles so he could HDR blend -- his comment as close as I can remember it was, "I have to shoot two because I can't get the full range from a single out of my Canon."
Best,
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Totally OT PS: I've discovered a problem with the ignore feature -- if somebody you have not put on your ignore list quotes somebody you have, you can see the quoted post. Not horrible, but like watching a train wreck you just cannot help yourself and in this case, I read the totality of nonsense I specifically tried to avoid...
/rant
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Totally OT PS: I've discovered a problem with the ignore feature -- if somebody you have not put on your ignore list quotes somebody you have, you can see the quoted post. Not horrible, but like watching a train wreck you just cannot help yourself and in this case, I read the totality of nonsense I specifically tried to avoid...
/rant
Yes, Jack... I get the same problem, but I ignore any post which quote the member I ignore.
It would be nice if other members (who normally make constructive posts) did not respond to, or quote, the member(s) we ignore!
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...I never get a sense in the real world ... of the apparent perspective distortion one finds in a wide-angle photographic image.
...Is this effect explained by optics or by the way the brain interprets ... ?
Ray,
I wrote an answer but I feel thats a sudden shift (our perception / limits of 2d reproduction). Hopping from topic to topic, not my cup of tea...
Christian
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It would be nice if other members (who normally make constructive posts) did not respond to, or quote, the member(s) we ignore!
For sure it would... But just like watching that train wreck, sometimes those comments are just so far out there and off base that it is difficult to let them go without comment. Problem is, some folks just refuse to accept they're wrong regardless of how absurd their position is