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Author Topic: Perspective Revisited  (Read 32387 times)

Fine_Art

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Re: Perspective Revisited
« Reply #40 on: January 30, 2012, 01:34:42 am »

After giving this matter some more thought, I think now see the reason for this difference of opinion about perspective and focal length of lens.

Whenever I compare technical qualities in images, such as resolution, noise or DoF etc, I always compare equal size images or prints, because that's the sensible thing to do.

I've been assuming all along that that's what everyone else does, but it seems this isn't the case.

Guillermo's example of his microwave taken with a 10mm lens, showing the crop lines for 17mm and 22mm can only demonstrate that perspective doesn't change provided the smaller images resulting from the cropping are not enlarged, and providing all the different sized images or prints are viewed from the same distance, which they are in his example.

However, this effect is not what happens when one looks through the camera's viewfinder using different focal lengths of lenses. The viewfinder remains the same size, but the objects viewed become enlarged as a result of any increase in focal length of lens.

Likewise, when making prints to hang on one's wall, or to sell to customers, one would not choose to make the size of the print inversely proportional to focal lengthof lens used, in order to maintain the original perspective, although one could if one so chose.

I think most of us would agree that it would be a very odd thing to do, if a photographer of wildlife were to exhibit his prints at postage-stamp size on the grounds that he wanted to maintain the original perspective before raising camera to eye, with telephoto lens attached,  to take the shot.

Most of us want to exploit that potential of the telephoto lens to change perspective and make things look closer. We revel in the close-up view with its extra detail and hyper-realism.



Magnification, showing more detail is not perspective. Perspective is not angle of view either. Angle of view is related to magnification.

Wherever you are light is entering your eye in a straight line from everything it came from. If you move a few steps away the things that were behind other things may come into view. All the light is still entering the eye in straight lines. You could shine a laser pointer out to them.

With a telephoto lens all you are doing is magnifying the detail in a smaller arc. It does not change perspective. Everything still lines up to the same points when you scan the lens around. I understand what you are saying that the person looking at the shot may assume you were close to the animal based on their memory of how things look when they are there. That is valid, they may well make assumptions. It isnt perspective its angle of view. If they had the ability to notice how flat the image looked they would guess it was from far away. If it was a wide angle shot they could guess from the magnification distortion that it was a wide lens. They would not assume for example that buildings shrank for the photo.

The perspective of a viewpoint is what is in line with the eye. The relative size of those things is not the perspective, it is magnification distortion.
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Ray

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Re: Perspective Revisited
« Reply #41 on: January 30, 2012, 06:21:45 am »

Magnification, showing more detail is not perspective. Perspective is not angle of view either. Angle of view is related to magnification.


Really! This is getting curiouser and curiouser. It seems pretty obvious to me that a change in the position of the viewer, whether the viewer is looking at 3-dimensional objects in a real scene or at a picture of that real scene hanging on the wall, will cause a change in angle between the line of sight from the eye to the proportions of the objects being viewed.

For example, if I view a tall building from such a distance that it looks very small, a mere detail in the landscape, the angle between the rays of light from the top of the building to my eyes, and the rays of light from the bottom of the building to my eyes, will be very narrow indeed. Agreed?

If I move up really close to the building, which will cause a change in perspective (I've never denied that. I'm not silly), then the angle between those rays reflecting from the top and bottom of the building to my eyeballs will be very wide indeed. Agreed!

How can you claim that perspective is not related to angle of view?

Please give an example of a change of perspective which does not involve a change in angle of view.
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Eric Myrvaagnes

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Re: Perspective Revisited
« Reply #42 on: January 30, 2012, 07:43:18 am »

Please give an example of a change of perspective which does not involve a change in angle of view.

Example:

Find two trees or other large objects that are a good 100 feet or more apart. Take a camera with your favorite fixed-focal length lens with you and go to a position where you are at least 500 feet from the nearer tree and where the more distant tree is still visible (that is, you are a little ways off from a straight line joining the trees, so you can see both of them. Take a picture of the two trees with a small lens opening and focused on the nearer tree.

Then, walk toward the nearest tree until you are about 20 feet from it, with the more distant tree still showing behind it. Don't forget to bring your camera and the same lens with you. Without changing the focus or lens opening from the first picture, take another picture of the two trees.

Since you used the same lens on the same camera, the viewing angle is identical in both images. But the perspective (as well as your invention of the "perception of perspective") will have changed.

Isn't this obvious? Please note that distortion will not have any different effect in the two images, since you used the same camera, lens, focus, and aperture for both pictures. Of course, the sun may have moved a little, or even gone behind a cloud between photos 1 and 2, but I hope even you won't consider exposure to be related to perspective.

Eric
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Ray

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Re: Perspective Revisited
« Reply #43 on: January 30, 2012, 09:53:42 am »

Example:

Find two trees or other large objects that are a good 100 feet or more apart. Take a camera with your favorite fixed-focal length lens with you and go to a position where you are at least 500 feet from the nearer tree and where the more distant tree is still visible (that is, you are a little ways off from a straight line joining the trees, so you can see both of them. Take a picture of the two trees with a small lens opening and focused on the nearer tree.

Then, walk toward the nearest tree until you are about 20 feet from it, with the more distant tree still showing behind it. Don't forget to bring your camera and the same lens with you. Without changing the focus or lens opening from the first picture, take another picture of the two trees.

Since you used the same lens on the same camera, the viewing angle is identical in both images. But the perspective (as well as your invention of the "perception of perspective") will have changed.

Isn't this obvious? Please note that distortion will not have any different effect in the two images, since you used the same camera, lens, focus, and aperture for both pictures. Of course, the sun may have moved a little, or even gone behind a cloud between photos 1 and 2, but I hope even you won't consider exposure to be related to perspective.

Eric

Eric, We both know I can walk anywhere I like, jump up and down, have dinner and change my clothes, but neither the viewing angle of my eyes nor the viewing angle of my lens will change, unless I attach another lens to the camera and /or change the magnification of my spectacles.

The angles that change are the angles that delineate the objects in the scene from the perspective of the eye or the camera lens/sensor. These angles will change if one changes position in relation to any fixed object in the scene.

The point I've been addressing all along, is not a denial that changing position changes perspective, but that there seem to be additional factors such as focal length of lens which contribute to a change of perspective, whether from the same position or a changed position.

As I'm sure you know, in order to demonstrate a point scientifically one should try to eliminate as many variables as possible.

In this digital age we experience image size in relation to pixel count. Irrespective of the size of the sensor, images of the same aspect ratio and pixel count will appear the same size at 100% on screen, or make the same size prints at the same ppi, without downsampling or interpolation.

So, if we're trying to demonstrate, like Guillermo has attempted, that focal length has no bearing on perspective, how about eliminating the variable of pixel count for a start, and use the same camera and same sensor with different focal lengths of lenses resulting in the same size image or print.

We could exagerate a little to get the point across. We could use a 12mm full-frame lens that captured almost the whole of the kitchen with Guillermo's microwave oven looking quite distant. Then we could use, say, a 100mm lens to fill most of the frame with just the microwave oven, both shots taken from the same position.
We could then display both images at the same physical size, say 24"x16" prints next to each other on the same wall, view them from the same distance, and ponder whether or not the perspective in both images is the same.

We know that the photos were taken from the same position. We know that the prints are viewed from the same position. We know that the camera and sensor are the same. The only variable is the focal length of lens.

That's the way to do it.  ;D
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JohnTodd

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Re: Perspective Revisited
« Reply #44 on: January 30, 2012, 01:13:28 pm »

Ray,

Would it be possible for you to upload a couple of pictures which demonstrate the effect you're talking about, so we can understand it by comparison?
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Guillermo Luijk

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Re: Perspective Revisited
« Reply #45 on: January 30, 2012, 02:35:32 pm »

I answer over your text:

So, my question to you, Guillermo, is do you agree with the following statements, and if not why not?

(1) Without the rest of the face visible, the size of the nose in relation to the eyes and ears, cannot be gauged in the telephoto shot. We cannot determine whether or not the nose is unusually large or not.

Correct. Both images would be undistinguishable.

(2) If we crop the wide-angle shot to the same FoV as the telephoto shot, we have effectively changed the focal length of the lens, thus demonstrating the principle that different lenses on different format cameras can have the same effective focal length. I've always argued that it's the effective focal length that counts, not the lens per se.

Incorrect. The focal length of a lens is a physical optical parameter, measured in mm. By cropping you only change the FOV. Different lenses on different formats can have the same FOV, not the same focal length. The term 'effective focal length' is incorrect, there is not such thing. There is just a FOV produced by the combination of a given focal length + sensor format. The term 'equivalent focal length' could be acceptable IMO, even if it doesn't refer to a focal length but to the FOV the lens would produce in a 35mm format.

(3) Whether the perspective distortion is caused by a change in focal length or a change in distance, it is a distortion in both cases, or an illusion if you like. Agreed?

The combination of perspective (which solely depends on distance) plus FOV (determined by the combination of focal length + sensor format) can make use perceive distorted subjects. The reason for this is basically because our visual system doesn't project images linearly nor has such a wide FOV as a wide angle lens can produce. This is why wide angle images look weird to us many times, because our eyes never produce them in real life. A wide angle image showing distortion is not incorrect, it's just a mathematical projection our visual system cannot produce by itself. Is this an illusion? I would rather consider it a mismatch between the image produced in the camera vs the images we are used to observe in real life.

(4) When I photograph a bird sitting on the branch of a tree from a distance of say 30 metres, using a telephoto lens, the image, or final print, really does give the impression the shot of the bird was taken from close up. If something in an image appears closer to the viewer than it actually was in reality, is that not perspective distortion? If not, what type of distortion or illusion would you call it?

Incorrect. It is not perspective, it is magnification, and as Fine_Art explained well this is related to FOV.

(5) I'm sure we can both agree that the big nose effect from a wide-angle lens is a distortion or illusion. But what happens when the subject for the portrait really does have a huge nose in reality? Well, we can create the opposite effect by taking the portrait with a 300mm or even 600mm lens (35mm format equivalent) from a great distance. The nose might then appear normal, and that would be an illusion, although  probably a nice illusion.

Correct. Perspective (i.e. subject distance) can be used to fake the perception of nose's size in a portrait. You can take a picture of a big nosed guy from a long distance, and make it look a smaller nose than a wide angle shot taken from a very short distance from a guy with a regular nose.



« Last Edit: January 30, 2012, 06:42:04 pm by Guillermo Luijk »
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Eric Myrvaagnes

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Re: Perspective Revisited
« Reply #46 on: January 30, 2012, 03:08:19 pm »

Ray,

Would it be possible for you to upload a couple of pictures which demonstrate the effect you're talking about, so we can understand it by comparison?
Excellent request. I tried to answer quite explicitly the exact question that Ray asked, namely "Please give an example of a change of perspective which does not involve a change in angle of view."

Photographing any scene with any one camera and the same fixed lens at different distances gives "a change of perspective which does not involve a change in angle of view" because the angle of view of any fixed lens is fixed (i.e, it doesn't change; that's why it's called 'fixed.')

But Ray's answer to me goes into completely unrelated territory so I have no idea what relation, if any, his comments have to "perspective."

Eric

P.S. Guillermo, on the other hand, makes complete sense.
« Last Edit: January 30, 2012, 03:11:09 pm by Eric Myrvaagnes »
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dchew

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Re: Perspective Revisited
« Reply #47 on: January 30, 2012, 04:47:36 pm »

Ray,
I think you have a very interesting point of view on this subject.  However, I keep coming back to what others have stated: this is all about the definition.  I have always thought of perspective as the relative size of things I see (sorry - imprecise layman's terms).  In photography the definition of perspective is "usually" limited to relative size and how it changes as you move closer to or farther away from subjects.  Our vision is of course no different than a camera in this regard.  If I stand 6" from a tree trunk it will encompass almost my entire view, and appear much bigger than another tree trunk 50 feet away.  But If I stand 50 feet away from the first tree trunk, the second one (now 100 feet away) will appear much closer in size to the front trunk.  Our brains know this and adjust for it but the camera doesn't.  This effect is what I call perspective.

You want to include other things in that definition of perspective.  That's fine if you want to do that.  The reason I don't want to do it is because it might confuse the definition of some of those other things.  For example, someone may ask why the bushes at the bottom corner of a wide angle shot are stretched and leaning?  Or why is the building tipping back? Or why is the dog's nose so big relative to his tail? Or why does the telephoto image look sharper vs. the center crop of the wide angle blown up to the same size?

For me it makes sense to relate each one of those questions/answers to a distinct (and different) cause/effect.  I get the sense you want to include some additional cause/effect into "perspective."  Again, fine.  But that's a debate about the definition of perspective.  And if we can't agree on the definition of something, then we obviously can't agree on what that "something" is or does.

Dave
« Last Edit: January 31, 2012, 12:05:11 am by dchew »
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Wayne Fox

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Re: Perspective Revisited
« Reply #48 on: January 30, 2012, 07:50:03 pm »

Ray,
I think you have a very interesting point of view on this subject.  However, I keep coming back to what others have stated: this is all about the definition.  ...

Dave
This has been the issue with Ray and perspective all along in the other threads.  He wants to roll other things into the concept of "perspective" and redefine it, and while I suppose if  you go by the broad definition of perspective it might be understandable, the term is very well defined and accepted in visual arts.  Trying to explain other phenomenon as part of perspective goes against the accepted definition, as this thread as so aptly pointed out.  Trying to roll FoV, distortion and perspective into one catchall concept of perspective seems illogical, especially since all three and their relationships are pretty well defined and understood by photographers  (and others involved in visual arts), and understanding them separately is important and beneficial whereas lumping them together doesn't accomplish anything.

Ray has a different perspective on perspective (sorry, couldn't help myself), and despite all of his attempts to convince others, nothing has changed.
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Eric Myrvaagnes

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Re: Perspective Revisited
« Reply #49 on: January 30, 2012, 09:16:01 pm »

While we're turning "perspective" into a universal catch-all concept, why don't we also throw in exposure, dynamic range, the ratio of curent value of the US dallar against the Canadian dollar, what I had for supper last night, and the number of colors in the third shirt that Jeff will be wearing in the LR4 video when it comes out? And, while we're at it, why not...

 ;)

I guess it's time to go take some pictures, folks.

Eric  ;D
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Fine_Art

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Re: Perspective Revisited
« Reply #50 on: January 31, 2012, 12:08:39 am »

Really! This is getting curiouser and curiouser. It seems pretty obvious to me that a change in the position of the viewer, whether the viewer is looking at 3-dimensional objects in a real scene or at a picture of that real scene hanging on the wall, will cause a change in angle between the line of sight from the eye to the proportions of the objects being viewed.

For example, if I view a tall building from such a distance that it looks very small, a mere detail in the landscape, the angle between the rays of light from the top of the building to my eyes, and the rays of light from the bottom of the building to my eyes, will be very narrow indeed. Agreed?

If I move up really close to the building, which will cause a change in perspective (I've never denied that. I'm not silly), then the angle between those rays reflecting from the top and bottom of the building to my eyeballs will be very wide indeed. Agreed!

How can you claim that perspective is not related to angle of view?

Please give an example of a change of perspective which does not involve a change in angle of view.


You are taking a picture of a famous sculpture or building that is down the end of the street. eg
http://www.oldnorth.com/history/index.htm

You take a picture from the sidewalk. It looks a bit cramped. You check for cars then move your tripod at right angles to take the shot from the middle of the street. You have changed your perspective. Your angle of view has not changed. The building is still the same size in relation to the other buildings.
« Last Edit: January 31, 2012, 11:55:46 pm by Fine_Art »
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Ray

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Re: Perspective Revisited
« Reply #51 on: February 02, 2012, 04:39:58 am »

I answer over your text:

Very brave!  ;D

2) If we crop the wide-angle shot to the same FoV as the telephoto shot, we have effectively changed the focal length of the lens, thus demonstrating the principle that different lenses on different format cameras can have the same effective focal length. I've always argued that it's the effective focal length that counts, not the lens per se.

Quote
Incorrect. The focal length of a lens is a physical optical parameter, measured in mm. By cropping you only change the FOV. Different lenses on different formats can have the same FOV, not the same focal length. The term 'effective focal length' is incorrect, there is not such thing. There is just a FOV produced by the combination of a given focal length + sensor format. The term 'equivalent focal length' could be acceptable IMO, even if it doesn't refer to a focal length but to the FOV the lens would produce in a 35mm format.

Guillermo, you will find that the terms "effectively the same" and "equivalent" are used interchangeably in the English language when referring to similarities in the focal length of lenses and other matters. The terms are synonymous. "Effectively the same" means "equivalent". If you disagree, I would describe that as a semantic quibble.

Here's one definition of equivalence from the Encarta Dictionary.

Quote
equivalence | equivalency:
The fact of being the same, effectively the same, or interchangeable with something else.

It is understood that two lenses of different 'actual' focal length, but equal 'effective' or 'equivalent' focal length as a result of cropping, are not necessarily equivalent in other respects, such as maximum F/stop, nearest focussing distance, vignetting, MTF response and a whole lot of distortions such as barrel distortion and volume anamorphosis.

It should also be understood, when attempting to compare the perspective in shots taken from the same position with different 'equivalent' focal lengths of lens, one should remove as far as possible such lens distortions from each shot in order not to prejudice the findings. The lens modules in ACR in CS5 do a pretty good job of removing or reducing many distortions, but don't appear to have any effect on volume anamorphosis. To fix that, one needs the sort of converter and lens modules provided by DXO Labs, or do it manually with Photoshop's free transform and warp.

Having successfully removed such distortions before the comparison of the perspective issue, one cannot prove that perspective is not affected by differences in 'equivalent' focal length, or FoV, by making the equivalent focal length the same in both images through cropping.

That would almost be like claiming that 2 = 5, and to  prove it I'll remove 3 from the 5. So, whilst it's not true that 2 = 5, it is true that 2 = 5 - 3.

The analogy here is that 2 = the shot with the long lens, and 5 = the shot with the shorter lens. The perspective in 2 is not equal to the perspective in 5, but it is equal if you subtract all the additional objects in the wider field of 5.

Your demonstration that FoV does not affect perspective, using the 10mm shot of your microwave oven, with overlay crop marks for 17mm and 22mm equivalence, is merely a tautology. You are basically stating the obvious that 2 (22mm) = 5 (10mm) minus 3 (cropping).

Let's consider again the example of the person with the big nose. I take a portrait with a standard lens that is not flattering but is accurately realistic because the big nose is very apparent. I decide to take another shot from a much greater distance which is more flattering, but I have only the one standard lens. However, my camera is an IQ180 with 60mp, and I reckon with the high quality pixels of the IQ180 I can make a reasonable A3 portrait from a crop consisting of 2 or 3 mp.

Now you are claiming that it makes no difference to the perspective distortion of the nose whether I use a 400mm lens or an 80mm lens to capture the head and shoulders portrait, whereas I'm suggesting that without the cropping and magnification of the 80mm shot, the perspective will not look distorted.

In other words, if the field size (how much of the subject and its surrounding area is visible) is different, then the sense of perspective in the image from the viewpoint of the viewer will be different. The perspective distortion will not be apparent when the subject is surrounded by similarly distorted and distant background objects.

If one crops a distant object, divorces it from its surroundings then enlarges it, the perspective that was seen as being natural for that object when viewed at a distance in a photo taken with a standard lens, will then become unnatural, although more flattering in our example.

There is also an obvious contradiction in your methodology of examing perspective based on identical distance from subject to viewer. In order to determine that the perspective of distant small objects in a narrow field cropped from a wide-angle shot is the same as another shot with a longer lens that encommpasses the same narrow field, you have to break the condition of equal distance. You have to get closer to the small crop to peer at it with a magnifying glass.

In other words, you are 'effectively' saying, "The perspective in shots taken with different 'actual' and different 'equivalent' focal lengths of lenses, from the same position, can be demonstrated as being the same, provided I convert both images to the same 'equivalent' focal length, and provided I change my viewing distance to the smaller crop from the wider-angle shot.

What a balls-up! What sort of a scientific method is this!  ;D

I'll repeat. The proper way to examine this issue is to eliminate all variables as far as possible. Keep the distance from the scene the same in all shots. Keep the camera the same and the print sizes the same. Don't 'doctor' the evidence by cropping in post-processing, which is tantamount to 'selection bias'. Don't make different size prints of the images being compared, and don't view such prints from different distances.

If you follow this sound scientific procedure, I think you will find that FoV does indeed influence the sense of perspective in a scene, in the mind of the viewer.

However, divorced from the viewer, the perspective does not change. But that's Alice in Wonderland stuff.  ;D
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Ray

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Re: Perspective Revisited
« Reply #52 on: February 02, 2012, 05:04:46 am »

You take a picture from the sidewalk. It looks a bit cramped. You check for cars then move your tripod at right angles to take the shot from the middle of the street. You have changed your perspective. Your angle of view has not changed. The building is still the same size in relation to the other buildings.

Of course your angle of view has changed. Any change in position, up or down, to one side or another, forwards or backwards, is a change in perspective and angle of view.

If it's a small change in position, the change in perspective and angle of view will probably be small. If it's a large change in position, the change in perspective will probably be large.

Changes in position, even though minor, can cause objects that were previously obscured to become visible, and objects that were previously visible to become obscured, because the angle of view has changed.

Changes in FoV can cause huge numbers of objects that were previously obscured to become visible.

Perhaps I should clarify what I mean by angle of view. I'm making a distinction between 'angle of view' and 'field of view'. The FoV of the lens/camera doesn't change as you change position, obviously. How can it? That's a property of the lens/camera system. What changes is the visual angle from the eye to the various objects within the field.
« Last Edit: February 02, 2012, 09:27:47 am by Ray »
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JohnTodd

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Re: Perspective Revisited
« Reply #53 on: February 02, 2012, 08:12:55 pm »

Ray,

Are you talking about the difference between the two attached images (when seen opened at full size)? To clarify, the pixel relationship between the toy dog and the distant building is exactly the same, the only difference is the presence or absence of surrounding detail.

John
« Last Edit: February 02, 2012, 10:38:21 pm by JohnTodd »
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Ray

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Re: Perspective Revisited
« Reply #54 on: February 03, 2012, 05:57:13 am »

Ray,

Are you talking about the difference between the two attached images (when seen opened at full size)? To clarify, the pixel relationship between the toy dog and the distant building is exactly the same, the only difference is the presence or absence of surrounding detail.

John


John,
The surrounding detail from top to bottom is exactly the same. All you seem to have done is change the aspect ratio of the image by cropping the sides.

During these discussions in other threads, it was mentioned that merely pointing the camera in a slightly different direction whilst standing in the same position, constitutes a change in position. One might quibble again over the semantics. Is a change in the angle a lens is pointing a change in position? One might more accurately describe it as a change in angle from the same position. However the effect of a change in angle can be quite dramatic. Merely pointing the camera slightly upwards or downwards can have a substantial effect on the verticals of buildings.

If you had taken those two shots, as presented, with different focal lengths of lens, you would have had to have either pointed the telephoto lens down slightly, or crouched down to a lower position. You would have needed to change position and you would have lost the top part of the image. As we all know, a change in position results in a change of perspective.

Now I'm travelling at the moment in Thailand. However, because I'm retired, a holiday can be as long as I want  it to be. I have no compulsion to rush around to see everything, and cram every sight-seeing opportunity into the available time. I can relax and continue many normal activities such as posting on LL. However, processing images on my notebook can be a bit of a chore. I'm reluctctant to bother because the results in terms of color calibration can be off.

Nevertheless, for the record I probably should photograph the view from the top floor of my current hotel. Even though it's not spectacular, it's fairly nice.

So here are the two shots, taken earlier today, using the same camera from the same position and angle, displayed at the same size, and presumably viewed from the same distance. The only significant difference is the focal length of the lenses used.

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Eric Myrvaagnes

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Re: Perspective Revisited
« Reply #55 on: February 03, 2012, 09:33:26 am »

So here are the two shots, taken earlier today, using the same camera from the same position and angle, displayed at the same size, and presumably viewed from the same distance. The only significant difference is the focal length of the lenses used.


And the "perspective" in both pictures is the same, although the difference in "field of view" makes things look closer in one than the other. Is this the effect you have recently been calling "perception of perspective?" The "effect of field of view" might be a better term, but if you want to define a term in a non-standard way, you would help your cause if you provided a clear definition of it.
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Guillermo Luijk

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Re: Perspective Revisited
« Reply #56 on: February 03, 2012, 09:43:34 am »

when referring to similarities in the focal length of lenses and other matters. The terms are synonymous. "Effectively the same" means "equivalent". If you disagree, I would describe that as a semantic quibble.transform and warp.

Your entire discussion about perspective IS about semantics.

But your particular view of what 'focal length' means is not a semantic discussion, you are simply wrong in this concept. There is no such thing as 'equivalent focal length' or whatever (no matter how many badly informed photographers use that term), because the focal length of a lens is UNIQUE. It is a physical parameter of the optics and is measured in mm. What you call 'equivalent focal length' refers to the field of view (FOV), and that's the proper word for it. And the FOV depends on the pair: focal length + format size (this including any pp cropping).

A 50mm is always a 50mm, no matter in which sensor size you put it. It's a 50mm on a FF camera, and it's a 50mm on an APS-C camera, but will provide a different FOV on both. A 50mm will provide on a FF body the same FOV as a 33mm on an APS-C camera, and a 50mm will provide on an APS-C camera the same FOV as a 75mm on a FF camera. As simple as this.

Regards
« Last Edit: February 03, 2012, 06:10:56 pm by Guillermo Luijk »
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Eric Myrvaagnes

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Re: Perspective Revisited
« Reply #57 on: February 03, 2012, 05:52:30 pm »

Your entire discussion about perspective IS about semantics.
Yes! Absolutely!

And it's worth repeating:
Your entire discussion about perspective IS about semantics.

And again, just to be certain:
Your entire discussion about perspective IS about semantics.

Eric
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feppe

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Re: Perspective Revisited
« Reply #58 on: February 03, 2012, 06:24:26 pm »

I can't believe the 2nd edition of this debate is going on for another four pages.

What is the authoritative scholarly source (read: a book) which someone could refer to settle this? I'm positive these things have been put on paper hundred plus years ago. Having such drawn out and controversial threads on some of the most basic subjects of optics on a supposedly pro photography and pixel peeper forum is truly incomprehensible, and frankly embarrassing.

Wayne Fox

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Re: Perspective Revisited
« Reply #59 on: February 03, 2012, 11:33:22 pm »

What is the authoritative scholarly source (read: a book) which someone could refer to settle this? I'm positive these things have been put on paper hundred plus years ago. Having such drawn out and controversial threads on some of the most basic subjects of optics on a supposedly pro photography and pixel peeper forum is truly incomprehensible, and frankly embarrassing.
A little embarrassing (for ray anyway). I guess embarrassing for others because keep bashing our heads against it and keep the thing alive.  I'm not sure about "scholarly" source, but there are probably 100's of places that talk about "perspective" as it relates to photography (including threads like this which contributors have made it pretty clear), and ray is the only person I've ever seen try to "redefine" the accepted understanding of the photographic world (and other visual arts for that matter).

It's semantics for sure, problem is their is an accepted meaning, ray just doesn't want to believe it because he wraps his own personal thoughts around it.

I's obviously pointless, even though not a single person as chimed in to "defend" his personal definition or decided he is right, he just doesn't seem to understand that while there might be some "logic" to his thought process, there is an accepted concept of perspective in photography (and other visual arts), that is valuable as it is, easy to teach and important to be separate from some of the other concepts he is trying to combine it with.
« Last Edit: February 04, 2012, 03:00:15 am by Wayne Fox »
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