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01-15-2012, 07:38 PM   #181
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QuoteOriginally posted by Yamanobori Quote
Now put all three uncropped images in the post at the same time. The 24mm will have greater perspective--it will also show more. Like I said, this is not simply image-size ratio which does not define perspective by itself. What you have most likely learnt is that the ratio of image size is directly proportional to the ratio of object distances. But that is not down to one distance, but a ratio

Here is one image with the cropped image next to it. It clearly shows the linear perspective, how fast the radial lines converge, are not the same. We will perceive the image on the left as having greater perspective or space or depth or whatever subjective term you would like..
You are using the word 'perspective' the same way the rest of us are using 'width'.

You also seem to be using the word 'perspective' to describe 'convergence'.

I don't know how to illustrate an angle in PSE, i'll bet you that if you compared the red lines on your picture, only looking at the portion covering the doors, you'd see that the angles are identical (although, it looks like the pictures were not taken at the same angle, but the distance looks pretty close).

Lets try word substitution with your post:

QuoteOriginally posted by Yamanobori Quote
Now put all three uncropped images in the post at the same time. The 24mm will have greater width--it will also show more. Like I said, this is not simply image-size ratio which does not define perspective by itself. What you have most likely learnt is that the ratio of image size is directly proportional to the ratio of object distances. But that is not down to one distance, but a ratio

Here is one image with the cropped image next to it. It clearly shows the linear convergence, how fast the radial lines converge, are not the same. We will perceive the image on the left as having greater width or space or depth or whatever subjective term you would like..
Yeah, that actually makes sense.

01-15-2012, 07:40 PM   #182
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QuoteOriginally posted by alohadave Quote
You are using the word 'perspective' the same way the rest of us are using 'width'.

You also seem to be using the word 'perspective' to describe 'convergence'.

I don't know how to illustrate an angle in PSE, i'll bet you that if you compared the red lines on your picture, only looking at the portion covering the doors, you'd see that the angles are identical (although, it looks like the pictures were not taken at the same angle, but the distance looks pretty close).

Lets try word substitution with your post:



Yeah, that actually makes sense.
Sorry, "width" should be "depth." Autocheck again.
01-15-2012, 07:43 PM   #183
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QuoteOriginally posted by Yamanobori Quote
Now put all three uncropped images in the post at the same time. The 24mm will have greater perspective--it will also show more.
There is no such thing as 'greater' nor 'lesser' perspective. Perspective is qualitative, not quantitative -- it can't be computed, unlike FOV. A shorter lens has greater (wider) FOV; a longer lens has smaller (narrower) FOV. But shots taken from the same distance with various lenses ALL have the same perspective, the same relationship of elements throughout the subject field.
01-15-2012, 07:46 PM   #184
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QuoteOriginally posted by jsherman999 Quote
Actually,, that's not true at all, it's common vernacular for what you think you're seeing, but a telephoto does not actually 'compress' space any more than am equivalent crop of a WA lens would.
But when people talk about telephotos compressing space, it is relative to a "normal" focal length taking the same shot while maintaining some subject in the frame at the same size. And that effect is very real -- the background will appear closer to the subject with the telephoto than with the wide angle. We've all probably seen those shots from the films Vertigo and Jaws that illustrate the concept.

01-15-2012, 07:54 PM   #185
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QuoteOriginally posted by alohadave Quote
You are using the word 'perspective' the same way the rest of us are using 'width'.

You also seem to be using the word 'perspective' to describe 'convergence'.

I don't know how to illustrate an angle in PSE, i'll bet you that if you compared the red lines on your picture, only looking at the portion covering the doors, you'd see that the angles are identical (although, it looks like the pictures were not taken at the same angle, but the distance looks pretty close).
You are now dealing with your person definition. I am simply dealing with the common definition of both perspective and linear perspective in photography--you can check something like the Focal Encyclopedia of Photography. And that example clearly shows linear perspective.

Your idea that I can change the size of the second image, which is just a crop of the first (although you could not recognize them perhaps because of the change in perspective), so that the lines match. But since linear perspective is radial, I can take any picture taken at any distance, at any focal length, with any crop, and register the radial line through scaling. That only proves that linear perspective is radial, but we know that.

The point is you do not display images in proportion to the format, the crop, or the focal length. Display size is held constant in that you make your images the same relative size regardless of the process.

I have shown a clear example that perspective does change though cropping or a change in focal length while keeping the camera position the same.
01-15-2012, 07:58 PM   #186
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QuoteOriginally posted by RioRico Quote
There is no such thing as 'greater' nor 'lesser' perspective. Perspective is qualitative, not quantitative -- it can't be computed, unlike FOV. A shorter lens has greater (wider) FOV; a longer lens has smaller (narrower) FOV. But shots taken from the same distance with various lenses ALL have the same perspective, the same relationship of elements throughout the subject field.
If perspective is "qualitative" how do you know that the elements have the same relationship? Can't you quantify that?

You are back to the fact that the ratio of images sizes are proportional to the ratio of object distances. That is a very basic concept. Not enough for perspective which deals with the apparent depth (3-D-ness) of a 2-D image.

Last edited by Yamanobori; 01-15-2012 at 08:03 PM.
01-15-2012, 08:04 PM   #187
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QuoteOriginally posted by Yamanobori Quote
You are now dealing with your person definition. I am simply dealing with the common definition of both perspective and linear perspective in photography--you can check something like the Focal Encyclopedia of Photography. And that example clearly shows linear perspective.

Your idea that I can change the size of the second image, which is just a crop of the first (although you could not recognize them perhaps because of the change in perspective), so that the lines match. But since linear perspective is radial, I can take any picture taken at any distance, at any focal length, with any crop, and register the radial line through scaling. That only proves that linear perspective is radial, but we know that.

The point is you do not display images in proportion to the format, the crop, or the focal length. Display size is held constant in that you make your images the same relative size regardless of the process.

I have shown a clear example that perspective does change though cropping or a change in focal length while keeping the camera position the same.
You have shown nothing of the kind. Please read the thread that jsherman linked. It has multiple examples illustrating that cropping an image does not change the perspective.

If you refuse to believe it, then there isn't much point in continuing this discussion.
01-15-2012, 08:08 PM   #188
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QuoteQuote:
Actually,, that's not true at all, it's common vernacular for what you think you're seeing, but a telephoto does not actually 'compress' space any more than am equivalent crop of a WA lens would.
This is one of those really irritating points of view , where in a person who'd like to be a know it all discusses a topic in such a way you would think they were an expert.. and this person isn't the only one to do it, as his quotes point out. The problem with the quote is that the author doesn't understand the original truth that brings up the vernacular saying, and doesn't address it when denying the inaccurate way of stating it that is open to argument. The fact is if an object is 12 feet in front of a brick wall.. and you take in image with an 18 mm lens and then count the number of bricks on each side of the object... then shoot it with a 200mm lens, moving back so the object is the same size.. and take another picture... you will count fewer bricks on either side of the subject with the 20mm lens...hence the back ground with the telephoto is considered to be compressed. This is well known by every studio photographer.. if you want to show less background behind your subject... move back and use a longer lens. That is what is meant by "compression." I can demonstrate it with my cameras, I can demonstrate it schematically. The fact that some people have mis-understood this concept, and made erroneous assumptions based on those mis-understandings... my point would be.. rather than say what isn't true, why not just explain at the same time what is? The use of a telephoto to compress a background is just one of those thing you have to be mindful of when you compose. Do I stand close at 60mm, or do I back up and use 250mm when shooting with my zoom. It's about a lot more than how you want the subject to look. Field of view affects selecting focal length of the lens to be used. It's about more than where is the most convenient place to stand. Keeping your subject the same size you can make your subject appear to be in the middle of a wide open expanse or in a much more compressed space, just by your selection of what focal length you use.

Don't even think I'm going to do an demonstration.. if you doubt, go give it a try. It's not the subject that is compressed, it's the background. Hence the notion that the room will look compressed with a longer lens, as long as you are comparing it to a subject that is the same size and the same distance from the background.


Last edited by normhead; 01-15-2012 at 08:18 PM.
01-15-2012, 08:14 PM   #189
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QuoteOriginally posted by alohadave Quote
You have shown nothing of the kind. Please read the thread that jsherman linked. It has multiple examples illustrating that cropping an image does not change the perspective.

If you refuse to believe it, then there isn't much point in continuing this discussion.
This is nothing to do with belief--I actually know my job, which this type of basic information falls under. What has been show is the ratio of image sizes are proportional to the ratio of object distances. But it has not been done well as he has not shown variation in camera position. However, it does not really show anything about perspective.

Well, if perspective has nothing do with converging lines, why do the parallel lines of a building converge when you look up? Why is it called "perspective correction" when you make them appear parallel again.

If you have no more to say, that is fine. But don't shoot the messenger.

Last edited by Yamanobori; 01-15-2012 at 08:23 PM.
01-15-2012, 08:21 PM   #190
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QuoteOriginally posted by Yamanobori Quote
This is nothing to do with belief--I actually know my job, which this type of basic information falls under. What has been show is the ratio of image sizes are proportional to the ratio of object distances. But it has not been done well as he has not shown variation in camera position. However, it does not really show anything about perspective.
Obviously you didn't even bother to read the thread, because changing the position is covered in that thread.

QuoteQuote:
Well, if linear perspective has do do with converging lines, why do the parallel lines of a building converge when you look up? Why is it called "perspective correction" when you make them appear parallel again.
Yes, you are correcting for linear perspective, but it has no impact on your positional perspective.
01-15-2012, 08:26 PM   #191
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QuoteOriginally posted by alohadave Quote
positional perspective.
Please define your personal term so I can try to understand what you are saying.
01-15-2012, 08:32 PM   #192
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QuoteOriginally posted by Yamanobori Quote
Please define your personal term so I can try to understand what you are saying.
The place where your camera is when you take a picture.
01-15-2012, 08:32 PM   #193
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The term compressed is as good as any really and would be called foreshortening by a painter. Perspective involves degrees of foreshortening with objects further from the observer being foreshortened more. When you 'magnify the crop or use a telephoto lens you are scaling up that foreshortening relative to the viewer. Perspective is something we learn to read and there are a few types of perspective to boot.
The easiest way of interpreting what I'm trying to say is to:
1: draw a horizon line with two radial points at each end on a piece of paper
2: draw mirrored radial lines from each point and where they intersect draw connecting lines to create a box.
3: draw radial lines for ever more 'distant' boxes
4: crop the central smallest box out and enlarge it to match the original larger box or paper size.

After doing this you will see that at the newer scale the perspective has changed as the angles for the newly enlarged crop are more foreshortened or compressed [than the previous larger/closer box]. The radial points are way off the paper now and as such the viewer has a new relationship to the space. If the object were way out on the horizon it would probably appear as flat and perspective would be reduced to zero point perspective as no further depth would be possible to describe linearly. Perspective is a perception and not an absolute truth.

We learn to read the 2D space of a photograph and probably fool ourselves a bit into believing it is an accurate representation of reality but it has been proven that some indigenous peoples could not 'read' photographs at first because they represent space in a different way in their art.
01-15-2012, 08:36 PM   #194
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QuoteOriginally posted by alohadave Quote
Obviously you didn't even bother to read the thread, because changing the position is covered in that thread.



Yes, you are correcting for linear perspective, but it has no impact on your positional perspective.
Would you define positional perspective for me? Are you referring to medieval and oriental means for describing space? [ or referring to overlapping objects ]

The latter methods of describing space are not what we are trying to discuss I feel. Chinese art depicts people the same size all over a scroll and they are deemed further away by placing them up the top of the work at the horizon etc... You know what the horizon is so your brain decides that anything between the bottom (foreground) and the horizon must be further away. The closest way a photograph could get to that scenario is to be looking down on a plain from a mountain top and get the whole HFD thing working. The higher the angle the more oriental it would look. The only hint as to distance might be a marginal size change of subjects and Arial Perspective (atmosphere)

Last edited by bossa; 01-15-2012 at 08:46 PM.
01-15-2012, 08:46 PM   #195
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QuoteOriginally posted by bossa Quote
Would you define positional perspective for me?
The place where your camera is when you take a picture.

QuoteQuote:
Are you referring to medieval and oriental means for describing space?
I'm referring to where the camera is when the picture is taken, and how it relates to different frame/sensor sizes.
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