Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: ErikKaffehr on August 16, 2009, 02:49:33 am
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Hi,
I would mention a couple of things regarding rendering of panoramas:
- Remove lateral chromatic aberration before merging, cannot be done afterwards.
- Perspective gets odd when shooting with camera tilted, take extra pictures beyond the expected panorama. I often find that corners are missing from my tilted panoramas.
- When preparing images for stitching I make them flat, trying to get a long tonal range. After stitching I optimize shadows, highlight, brigtness, clarity, vibrance. This would be done in Lightroom, in my case.
- It's probably best to work in 16 bits.
Best regards
Erik
Ps. I have some write up about pano shooting here: http://83.177.178.241/ekr/index.php/photoa...a-and-stitching (http://83.177.178.241/ekr/index.php/photoarticles/panorama-and-stitching) , it's work in progress.
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Good set of basic points.
-In cases where you lose the corners to rounding in Cylindrical projection, the Vedutismo projection can sometimes be helpful, it spreads the vertical borders up and down in relation to the center. PTGui has it, I think also Panorama Tools.
-Can be useful to correct for vignetting in the raw developer, helps with sky blending.
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I have had best luck by stitching more portrait oriented frames than less landscape orientation frames, less distortion and vignetting in the overlap, smoother sky blending
Marc
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You have a good write-up there. A few more comments:
I, too, find that portrait-oriented frames work best.
One thing that I find is important to do to minimize losing parts of the expected picture because of distortion is to use a tripod, make sure it's level in *both* directions using a bubble level placed on top of it, *then* put the camera on the tripod and use the bubble level again to make sure the camera is level too (at least in the side-to-side direction - the camera can be pointed somewhat up or down as required for the shot).
Rather than a fancy panning clamp, I use a small, simple RRS rail between the tripod head and camera to position the lens's nodal point in the right place to avoid parallax. I calibrated the rail's position on the tripod head for several focal lengths (I use a single zoom lens) at home, and have a paper sticker on the rail with pencil marks to indicate where to position it for those focal lengths. (Interpolate in between as necessary.)
It's probably obvious, but make sure to use manual exposure mode with the same exposure for all the frames (do a couple of test shots first in the brightest direction to get the exposure right), don't use a polarizer, and use identical settings (including the same color temperature!) for all the frames in your raw converter.
Snap all the frames *fast* to minimize cloud movement!
Lisa
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- Learn to visualize a scene without a viewfinder,
- Invest in massive and very fast storage,
- Buy new glasses and get ready to deal with very sharp images like this downsized 60 megapixel sample...
http://www.flickr.com/photos/bernardlanguillier/3833720762/ (http://www.flickr.com/photos/bernardlanguillier/3833720762/)
Cheers,
Bernard
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- Learn to visualize a scene without a viewfinder
That's one of the hardest things! It's so easy to shoot a framing that is totally off the wall.
I have gotten into the habit of holding my arms out at 160 degrees or whatever, then bending them up at the elbows while twisting my body left and right for framing via peripheral vision. More than once somebody has come along and asked me if I was giving adulation to the mountains or trees or the sky.
Another good way is to pan your camera rapidly left and right while looking through the viewfinder. With some cameras you can look at the pictures you have taken ganged up on the screen, nice if you can get them arranged side by side. When in doubt shoot more left and right and up and down even if it means going to a double row rather than a single one. Nothing worse than ALMOST getting a great pano.
I also have an old Leitz 100 degree finder which is helpful for finding the right vertical framing.
Nice pano, Bernard! For those who don't know that's just a little one, a mere 62mp. Just enough to make a decent 30 x 50 inch print. Panographers think of those as wallet-sized.
And massive storage is right! A good panographer will always have his drives nearly full.
-Don't neglect to explore the scene and the points of view carefully before picking your location. Wrangling the tripod + camera + panohead is a little intimidating at first, too often budding panographers just set up in any old spot without exploring the possibilities first.
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Nice pano, Bernard! For those who don't know that's just a little one, a mere 62mp. Just enough to make a decent 30 x 50 inch print. Panographers think of those as wallet-sized.
Indeed, just picked 60MP as it corresponds to the largest resolution currently available with single frame sensors.
What I find most remarkable with this image actually is more the DR than the detail. Common sense would dictate that a scene like this one can absolutely not be captured well without relying on HDR techniques, and this image is a clear proof that with the latest DSLRs there are many cases where proper exposure and adequate post-processing is enough.
Of course this is not a totally final version and it can still be improved a little bit.
-Don't neglect to explore the scene and the points of view carefully before picking your location. Wrangling the tripod + camera + panohead is a little intimidating at first, too often budding panographers just set up in any old spot without exploring the possibilities first.
Indeed, but that is also true for traditional single frame captures.
Cheers,
Bernard
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Basic, but take a shot of (e.g) one hand before and after the sequence, which makes it easy to identify the beginning and end of the sequence when it comes to stitching. I guess one could take this further and point the hand appropriately when stitching several rows.
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- if you dont shoot RAW: set everything to manual and make sure to use the same settings for all images that will be sticthed together (Exposure, WB, Autofocus Off)
- if you do shoot RAW: process all images with identical settings!
- if you have moving subjects make sure to capture the subject in one frame, shoot multiple frames to choose from later
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- if you have moving subjects make sure to capture the subject in one frame, shoot multiple frames to choose from later
That's a good one. If you have something moving in the scene like tourists shoot 2 or 3 images at each position, give the moving objects time enough to move a little more than their width between frames. That way you can stack the individual images in PS, and paint out the tourist with an image mask to reveal the section that was behind the tourist from a different "clean plate" where the background is not blocked. A pair of masks completely knocks the annoying tourist out of the scene without creating any stamping distortions.
Rubber stamping works too, but clean-plate technique works best if the behind-the-tourist texture is unique in the scene or complex.
It's even possible to completely remove crowds of people from around a building by shooting enough images and using enough masks, with maybe also a touch of the old rubber stamp here and there.
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- if you dont shoot RAW: set everything to manual and make sure to use the same settings for all images that will be sticthed together (Exposure, WB, Autofocus Off)
- if you do shoot RAW: process all images with identical settings!
1. There is no need to make all shots with the same focusing distance. In fact, one of the greatest advantages of panorama/mosaic shooting is, that the DoF can be greatly enhanced by refocusing between the frames.
2. There is no reason to shoot all frames with the same exposure if recording the raw data. However, if the exposure is not the same for all frames, then it is highly probable, that the frames have to be developed with different parameters.
Update: I just realized the above There is no reason to shoot all frames with the same exposure is very badly worded. There is good reason to keep the exposure constant, namely the easier post processing. What I wanted to express is, that this is not an absolute requirement. There can be several reasons to change the exposure between frames. This makes the raw development and/or the post processing more laborous in most cases, but the advantage (usually the expansion of the dynamic range of the pano) is sometimes crutial.
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- If you're shooting scenes with flags or similar stationary but fluttering objects, shoot them also with a long focal length and high ISO to freeze them to your liking - paste them to the final rendering
- Get a shot or two of the sky with a wide angle lens - resolution doesn't matter as much, and you can use it to patch up any problem areas. Same goes for water.
It's even possible to completely remove crowds of people from around a building by shooting enough images and using enough masks, with maybe also a touch of the old rubber stamp here and there.
There's a utility called Amenebar made by our own Guillermo Luijk which does just that.
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Bernard,
I like both your writings and panoramas but I'd suggest that this image is just to big in this context. This discussion was intended to collect ideas, and having such a big image loading automatically just makes for a less than pleasant experience. The image is great, I'd just would prefer a clickable link.
Thank's a lot for all of your contributions.
Best regards
Erik
- Learn to visualize a scene without a viewfinder,
- Invest in massive and very fast storage,
- Buy new glasses and get ready to deal with very sharp images like this downsized 60 megapixel sample...
<A HREF="http://farm3.static.flickr.com/2622/3833720762_f3d9e1196f_o.jpg">A great image</a>
Cheers,
Bernard
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Use a high res digiback on a view camera and shift-and-stitch rather than pan-and-stitch.
Use the movements to let you use wider apertures and faster shutter speeds e.g. for foreground water, waves, waterfalls etc.
Use a wireframe viewfinder.
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Bernard,
I like both your writings and panoramas but I'd suggest that this image is just to big in this context. This discussion was intended to collect ideas, and having such a big image loading automatically just makes for a less than pleasant experience. The image is great, I'd just would prefer a clickable link.
Thank's a lot for all of your contributions.
Seconded. Non-thumbnailed images should be disabled on the board, but I'm not an admin - a 10,000x6,000 image is overkill especially in this context.
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Use a high res digiback on a view camera and shift-and-stitch rather than pan-and-stitch.
Only if you are happy with medium resolutions for the resulting pano and reasonnably classical aspect ratios.
Cheers,
Bernard
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Use a high res digiback on a view camera and shift-and-stitch rather than pan-and-stitch.
Only if you are happy with medium resolutions for the resulting pano and reasonnably classical aspect ratios.
Cheers,
Bernard
Hi, Bernard, what do you call medium resolutions?
With the 8 cm of shift on a Sinar P2, in conjunction with a multi-row sliding stitching back, you can get any aspect ratio you want, and very high-res files.
I am thinking of getting a Schneider Fine Art Gold 1100 and making a computer controlled multi-row stitching system that could create Giga-pixel pictures.
With a 4:3 ration back you can get 8* 3 and 4* 6 with 2 images (without allowing for overlap).
Using a 6708 * 8956 pixel (60Mpx) back you can print 18" * 24" @ 360 original camera pixels per print inch without scaling, uprezzing, distorting or stitching, but with single row stitching you can get 24 * 32, 48 or whatever, making good use of a 24" printer. I am thinking of getting a 60 inch printer for multi-row stitches.
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A significant characteristic of shifting backs is you are stuck with the classic wide angle perspective. The look is distinctly wide angle, the viewer is necessarily pulled in strongly towards the center of the image.
The basic cylindrical projection in typical panos removes the left right perspective entirely. The look is completely different. Either there is no perspective, or looking at it differently, every part of the cylindrical image is the center of perspective. The sense you get from a cylindrical pano is of being "in the place" rather than of being drawn forward to the center. You can more easily roam your eye around inside a cylindrical pano without sensing the peculiarties of an off-center wide angle perspective. Not to say one is better than the other, but to my eye nothing takes a picture of a PLACE better than a cylindrical pano. A wide angle perspective is more about a single object within the place, near the center.
One significant advantage of stitches over shifting is that in a stitch virtually every part of the image is the optical sweet spot. There are no optical differences or increase in aberrations as you go out from the center, the edges are as crisp as the center. Also, image sensors don't like light coming in at severe angles, beyond the any aberrations of the optics you get additional aberrations from light intercepting the sensor at steep angles. And dirt, wow is dirt ever a problem with a sensor exposed to the inside of a belows!
Sixty inch printers sure are nice. But for 1/3 the price a 43" x 120" pano looks pretty doggone hefty on just about any wall. Any bigger and you would probably want to do diptychs and triptychs anyway for logistical purposes.
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For really wide FOV's I agree with Bill, a rectilnear projection stretches things out too much at the edges of the frame (on the other hand sometimes cylindrical projections compress the horizontal FOV too much).
But stitching isn't always about super-wide FOV's, sometimes it's just to increase reslution and for that I think using flat-stitching with shift often produces more pleasing results.
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Ran into my first parallex error in stitching yesterday! Using a wide lens with rectilinear stitching and shooting a scene through window bars just 1 meter away. Pretty much to be expected actually. Never had parrallex before in my life due to excellent software corrections and I've never used a nodal slide either. Some subjects will defeat even the parallex killing Autopano Pro it seems.
I find it's easy to compose, I compose with the lens whose perspective I require, frame and shoot. I then note where to start and end on each axis, zoom in and start shooting frames making sure I have enough space outside of the area needed to allow vanishing point and distortion corrections. Dead easy. That way I don't have to imagine the final image, I see it through the viewfinder with the final perspective before I even start to shoot the frames needed to make it up.
(http://www.studio-beni.net/Tzfat_Vines.jpg)
Tzfat (Safed) Vines, 37 megapixels, shot yesterday.
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Hi!
I'd say I agree with both of you. One important issue on my mind is that this is not about equipment but about taking pictures. Start shooting panos and start stitching, learn by doing. If you need better stuff you can buy them later, but missed opportunites are, well, missed opportunities.
Shoot, stitch, learn from experience...
Best regards
Erik
For really wide FOV's I agree with Bill, a rectilnear projection stretches things out too much at the edges of the frame (on the other hand sometimes cylindrical projections compress the horizontal FOV too much).
But stitching isn't always about super-wide FOV's, sometimes it's just to increase reslution and for that I think using flat-stitching with shift often produces more pleasing results.
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With due respect...
I got plenty of good suggestions and even a big nice image on this posting. I would like to add most of the suggestions to my page, with due credits to all who have posted. I hope it's OK?
It will take some time as I leave for vacation tomorrow.
Thanks for input. I hope it will be helpful for the community.
Best regards
Erik
Hi,
I would mention a couple of things regarding rendering of panoramas:
- Remove lateral chromatic aberration before merging, cannot be done afterwards.
- Perspective gets odd when shooting with camera tilted, take extra pictures beyond the expected panorama. I often find that corners are missing from my tilted panoramas.
- When preparing images for stitching I make them flat, trying to get a long tonal range. After stitching I optimize shadows, highlight, brigtness, clarity, vibrance. This would be done in Lightroom, in my case.
- It's probably best to work in 16 bits.
Best regards
Erik
Ps. I have some write up about pano shooting here: http://83.177.178.241/ekr/index.php/photoa...a-and-stitching (http://83.177.178.241/ekr/index.php/photoarticles/panorama-and-stitching) , it's work in progress.
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I got plenty of good suggestions and even a big nice image on this posting. I would like to add most of the suggestions to my page, with due credits to all who have posted. I hope it's OK?
It will take some time as I leave for vacation tomorrow.
I'm fine with that. Have a great vacation!
Lisa
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A significant characteristic of shifting backs is you are stuck with the classic wide angle perspective. The look is distinctly wide angle, the viewer is necessarily pulled in strongly towards the center of the image.
Wide angle, and their over-use for landscapes are my pet hates - I am thinking that the 100 degree fov of the Schneider apo-digitar 47XL, with shift and stitch will save me having to buy an ultra-wide-angle.
I expect to use cylinder panos for cylindrical subjects, but for a high def pic of a building or two I would use a long focus lens (e.g. 210 mm on mf) and shift and stitch.
I am thinking about doing some long panos of harbours and bays, with some sections cylindrical and some shifted!
One obvious tip is:
To shoot panoramic pictures, use a panoramic camera
See
www.roundshot.ch
The Seitz/roundshot D3 digital pano camera is not cheap, but you can use the digital capture unit on their other cameras, so you do not have to do panos all the time to justify the cost.
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Bernard,
I like both your writings and panoramas but I'd suggest that this image is just to big in this context. This discussion was intended to collect ideas, and having such a big image loading automatically just makes for a less than pleasant experience. The image is great, I'd just would prefer a clickable link.
Thank's a lot for all of your contributions.
Best regards
Erik
Sorry Erik, just back from a 4 days trek and read your comment. Totally agree, I didn't intend to paste the image directly... pasted the wrong link. Just corrected that.
Cheers,
Bernard
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if you've got a building or other object with straight lines, make sure you capture the whole thing in one frame. If you are going more than one frame with a straight-lined object, you will need to either shift stitch, accept the bowing line, or plan for extra post-prod time.
If you're going for a panoramic, have a reason to go wide. Don't get caught up in technical things and forget that the composition needs to work for that kind of framing. Think about ways that moves the interest through that kind of framing.
And while we're at it, one of mine from a trip through the Canadian Rockies. 6 frame pan.
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if you've got a building or other object with straight lines, make sure you capture the whole thing in one frame. If you are going more than one frame with a straight-lined object, you will need to either shift stitch, accept the bowing line, or plan for extra post-prod time
If a line in the pano will be bowing or not has nothing to do with the number of frames but with the field of view of the line (not of the individual frames) and with the chosen projection.
The real issue with clear lines is the parallax problem; this has nothing to do with straight or not. For example electric lines in adjacent frames are not easy to join seemlessly if the camera's adjustment was not accurately around the entrance pupil.
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If a line in the pano will be bowing or not has nothing to do with the number of frames but with the field of view of the line (not of the individual frames) and with the chosen projection.
The real issue with clear lines is the parallax problem; this has nothing to do with straight or not.
The problem of straight lines across multiple panned frames is related to how the sensor's orientation to that line changes when you pan. Even after zeroing out the parallax change, you still have the fundamental problem of mapping a spherical world onto a flat sensor plane. If you pan, you change that relationship. It is not as noticeable with rounded natural features found in nature, but if you try to do it with a pan stitch with several parts of, say a building, those lines will not come together without a bent angle in between. No matter how accurate your entrance pupil is aligned, the sensor has moved and that has affected how a straight line will map out across it.
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The problem of straight lines across multiple panned frames is related to how the sensor's orientation to that line changes when you pan. Even after zeroing out the parallax change, you still have the fundamental problem of mapping a spherical world onto a flat sensor plane
Tyler, I'm afraid you are using a stitcher, which is not up to the job. *If* there is no parallax error, then the stitcher must not have any problem with transforming the images such way, that they perfectly join. Straight lines may have to be bent, depending on their orientation and on the projection, but if so, then that has to occur even if that line is within a single frame.
Do you happen to have a sample pano illustrating the problem? (But a somewhat larger one than the thumbnail you posted above, pls.)
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If a line in the pano will be bowing or not has nothing to do with the number of frames but with the field of view of the line (not of the individual frames) and with the chosen projection.
You're right to a certain extent, but once you get into multi-row panos with fairly large fields of view, it gets much more complicated. I've found that for instance if shooting buildings you're better off sticking to single-row cylindrical panos, unless you have a lens that allows vertical shift. Because as soon as you tilt the camera up/down between rows you have a perspective problem and the edges of the buildings will no longer be straight.
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as soon as you tilt the camera up/down between rows you have a perspective problem and the edges of the buildings will no longer be straight
You don't have a perspective problem but a parallax problem. This is typical with a simple rail setup, which allows for rotation around the entrance pupil but not for tilting.
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The problem of straight lines across multiple panned frames is related to how the sensor's orientation to that line changes when you pan. Even after zeroing out the parallax change, you still have the fundamental problem of mapping a spherical world onto a flat sensor plane. If you pan, you change that relationship. It is not as noticeable with rounded natural features found in nature, but if you try to do it with a pan stitch with several parts of, say a building, those lines will not come together without a bent angle in between. No matter how accurate your entrance pupil is aligned, the sensor has moved and that has affected how a straight line will map out across it.
You've got to wonder how these lines got straight...
http://www.flickr.com/photos/bernardlanguillier/3833720762/ (http://www.flickr.com/photos/bernardlanguillier/3833720762/)
Most efficient panorama softwares (PTgui and autopano Pro) are pefectly able to map a faceted cylinder on a plane in such a way that straight lines remain perfectly straight and that has been the case for many years.
Cheers,
Bernard
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Lots of good advice on this thread. Here is a short blog entry about panoramic projections: http://www.trailpixie.net/photography/comparing_focal.htm (http://www.trailpixie.net/photography/comparing_focal.htm)
Some general comments:
1) Several folks have said that you need to shoot in manual mode and lock the focus. This is good advice for many circumstances, but you can stitch images at different exposures....and you may even want to do that if there is lots of dynamic range. When you use this technique, make sure to increase overlap.
2) Two techniques to help you take rapid fire panos:
[blockquote]A. Shoot raw (always a given for me) and then use the exposure lock button to rapidly make a pano without the effort of changing modes. The exposure lock button allows you to set the exposure to one setting across multiple exposures.
B. I also have mapped the focus function to the AF button on the back of my canon. This allows me to focus on a single focal point of the pano, then recompose and set exposure (see above). By keeping my finger off the button for the duration of the multiple frames, I don't have the camera refocus. [/blockquote]
3) I frequently process my raw files differently to provide the illusion that the light level is remaining somewhat constant. I set the white balance and exposure for all the images, then work back across those that are either too dark or too light to shift them subtly towards the exposure I wanted from my key image.
4) When you shoot panos, remember to note the starting angle on your panning clamp. I can't count the number of times I have failed to do enough exposures on the second row. http://www.trailpixie.net/panoramics_go_b.htm (http://www.trailpixie.net/panoramics_go_b.htm)
5) When shooting water scenes, try to get stationary objects that can be used as control points into every frame. If this is impossible, manually create the control points and guess about their location. You may need to do some manual blending later.
6) Partly cloudy, breezy days are the bane of the panoramic photographer's existence.