Perspective VS Field of View...Debate

I have to start this debate again.

Scenario 1
ON A FULL FRAME BODY, you have the 24L (we will call this body A)
ALSO ON A CROP BODY (1.6x) you have another 24L (we will call this body B)

So we know that the FOV on body A will be 24mm and FOV of Body B will be 38.4mm

Body B gives us the EXACT same image as body A, however we just don't see the edges of it (cropped)
Therefore, Doesn't that mean the PERSPECTIVE, has not changed, since the same lens is used. ONLY FOV has changed.
So an object in the center of the frame WILL appear to be the same distance to its background (equal perspective)

Scenario 2
On body A we have a 16-35L
On body B we have a 10-22 (eqiv 16-35)

Both now have an EQUAL FOV, but the perspective of BODY B will be Greater, that is, the object in the center of the frame will appear to have a greater distance to its background.


BUT, we're not done yet.....

Canon EF Lens Work III states, and i quote "...Perspective is related to angle of view, so even if the focal length is different for each particular lens, if the resulting angle is the same due to the difference in image size...the perspective will remain unchanged, too" from page 149

So Canon's definition, clearly states that in particular, Scenario 2 is wrong.

Who is right?

I agree with Canon based on what I consider to be "perspective." To me, "perspective" simply means the angle from which you are shooting a subject. High, Low, Near, Far, etc. Far from something is still far away whether you're shooting with an UWA or a Super Telephoto lens. Above is always above, below is always below, etc. Shooting a coin at an oblique angle (for example) will always yield an elipse and not a circle. Doesn't matter if you're right on top of it with a Macro lens or a block away with a 1200mm f/5.6...

FlyingPhotog wrote in post #4914490
To me, "perspective" simply means the angle from which you are shooting a subject. High, Low, Near, Far, etc. Far from something is still far away whether you're shooting with an UWA or a Super Telephoto lens. Above is always above, below is always below, etc. Shooting a coin at an oblique angle (for example) will always yield an elipse and not a circle. Doesn't matter if you're right on top of it with a Macro lens or a block away with a 1200mm f/5.6...

I'm still not 100% convinced, but I can see what you mean.

The human eye is said to have a "perspective" of 50mm, but the angle of view is much wider in terms of 35mm SLR.

just say you have your 5D, and a lens with FL of 25mm.
you also have a medium format with crop factor of 0.5x, with FL of 50mm.

both have equal field of view. but wouldn't the medium format give a more 'real' sense of perspective (equiv to human eye). wouldn't the 5D have more distortion, (looks stretched from foreground to background)?

I almost understand completely,just need to tip me over the edge..
thanks for the input.

FlyingPhotog wrote in post #4914490
Shooting a coin at an oblique angle (for example) will always yield an elipse and not a circle. Doesn't matter if you're right on top of it with a Macro lens or a block away with a 1200mm f/5.6...

I wasn't gonna touch this with a 10-foot pole, but I will.

While what you say is right, if you fill the frame with the coin though, you have to change your distance depending on your focal length, and it's this change in distance that DOES change the perspective, even if the angle you're shooting at is the same. Fill the frame with a coin with a wide angle lens (i.e. standing close), and the front of the coin will look larger. Fill it with a longer lens (standing further away), and the back of the coin will look bigger.

What Canon said might actually be correct, but poorly worded. Here's my take on it.

"..Perspective is related to angle of view, so even if the focal length is different for each particular lens" - Here by focal length, I'm pretty sure they are referring to effective field of view since they say 'for each particular lens'. So even though an 85mm lens on a crop camera looks like a 136mm in terms of field of view, your positioning is the same, and so the perspective is the same.

"if the resulting angle is the same due to the difference in image size...the perspective will remain unchanged, too" - I actually have no idea what they are getting at here, I have no clue what 'difference in image size' is referring to. And am starting to doubt my interpretation in the above paragraph because of that, I can see the other way of interpreting this now...

perryge wrote in post #4914977
"if the resulting angle is the same due to the difference in image size...the perspective will remain unchanged, too" - I actually have no idea what they are getting at here, I have no clue what 'difference in image size' is referring to.

I think what they mean by "resulting angle" is angle of view, and "difference in image size" refers to equivalent angle of view for different cameras.

So heres how it sounds to me. "if the angle of view is the same for both cameras, regardless of sensor size, perspective will remain unchanged."

I disagree with this point however.

So by resulting angle of view they don't mean effective field of view. That makes sense.. If by angle of view they mean where you are standing and aiming, then this is fine.

If you stand in one place, and aim your camera in one direction, as you change focal lengths, perspective won't change. The image will change drastically because of the field of view, but the perspective will remain the same.

Perspective is entirely a function of your positioning, not of field of view.

Having said that though, it makes the statement 'a 50mm lens yields a perspective similar to the human eye' seem off. That is, until you make the distinction between focal length (not effective focal length) and field of view.

Ahhhhhhhhhhhhh brain asplode.

Where are the big guns (Skip, I'm talkin' to you here!) when you need them to put things simply, concisely, and clearly?

Chiva wrote in post #4914444
I have to start this debate again.

Scenario 1
ON A FULL FRAME BODY, you have the 24L (we will call this body A)
ALSO ON A CROP BODY (1.6x) you have another 24L (we will call this body B)

So we know that the FOV on body A will be 24mm and FOV of Body B will be 38.4mm

Body B gives us the EXACT same image as body A, however we just don't see the edges of it (cropped)
Therefore, Doesn't that mean the PERSPECTIVE, has not changed, since the same lens is used. ONLY FOV has changed.
So an object in the center of the frame WILL appear to be the same distance to its background (equal perspective)

Depends on how you define 'perspective'. 'Linear perspective' is the size relationship of objects to each other, and since both cameras are at the same position, the linear perspective has not changed at all.

But a different use of the same term 'perspective' is the perception that you and I have as viewers of a photo, and because the smaller format crops off the outer areas of the image, the 'perspective' has changed in this connotation although not in the context of 'linear perspective'.

Chiva wrote in post #4914444
Scenario 2
On body A we have a 16-35L
On body B we have a 10-22 (eqiv 16-35)

Both now have an EQUAL FOV, but the perspective of BODY B will be Greater, that is, the object in the center of the frame will appear to have a greater distance to its background.

Equal FOV captured onto the respective format sensor, but there is NO difference in the 'linear perspective' because the camera position has not changed.

And if the term 'perspective' is the perception that you and I have as viewers of a photo, they might seem to have the same perspective as well, if magnified by different amounts to the same final size, but the DOF is different so in that sense 'perspective' is somewhat altered.

Chiva wrote in post #4914444
BUT, we're not done yet.....

Canon EF Lens Work III states, and i quote "...Perspective is related to angle of view, so even if the focal length is different for each particular lens, if the resulting angle is the same due to the difference in image size...the perspective will remain unchanged, too" from page 149

So Canon's definition, clearly states that in particular, Scenario 2 is wrong.

Who is right?

As indicated, there are more than one definition of 'perspective'. If the images are both magnified by the same enlargement factor, they contain the same content, same FOV, they have the same DOF if viewed from proportional viewing depths related to print size

The different distance of camera to subject will change the viewing angle so even if the relative size of subject to background is the same how they appear on the image will differ...
If you put an 80mm on the full frame and the 50mm on the 1.6x bod and shoot FROM THE SAME DISTANCE then both the perspective AND appearance will be the same as the viewing angle would be the same...my understanding is that depth of field will differ tho.

kitacanon wrote in post #4915078
The different distance of camera to subject will change the viewing angle so even if the relative size of subject to background is the same how they appear on the image will differ...
If you put an 80mm on the full frame and the 50mm on the 1.6x bod and shoot FROM THE SAME DISTANCE then both the perspective AND appearance will be the same as the viewing angle would be the same...my understanding is that depth of field will differ tho.

Edit: I re-read your post, I misread it the first time, forget what I said.

kitacanon wrote in post #4915078
my understanding is that depth of field will differ tho.

yes, a longer focal length will yield a shallower depth of field than a wider lens. therefore the full frame will have less depth of field compared to the crop set to a wider FL.

consider this, telephoto lenses compress perspective.
the longer the FL the more compression of perspective
so if the full frame has a little more FL, then wont the perspective be more compressed.

canon says that Perspective is related to angle of view (or field of view)
we know that Focal Length is also related to angle of view.
So perspective is related to focal length.
therefore as focal length changes, so too should perspective.

Chiva wrote in post #4915146
canon says that Perspective is related to angle of view (or field of view)
we know that Focal Length is also related to angle of view.
So perspective is related to focal length.
therefore as focal length changes, so too should perspective.

I'm pretty sure angle of view doesn't mean field of view. So if premise 1 and 2 are false, 3 doesn't follow and the conclusion in 4 doesn't follow either.

Also, even if it does mean field of view, premise 1 isn't true anyway as perspective is not related to field of view in any way. Field of view is a function of focal length and sensor size, so if you're trying to derive a conclusion about the relationship of focal length to perspective from a premise about perspective as a function of something that is a function of focal length, the argument is begging the question anyway.

Sorry...I study philosophy, with a heavy emphasis on logic, couldn't help it

Chiva wrote in post #4914444
I have to start this debate again.

Scenario 1
ON A FULL FRAME BODY, you have the 24L (we will call this body A)
ALSO ON A CROP BODY (1.6x) you have another 24L (we will call this body B)

So we know that the FOV on body A will be 24mm and FOV of Body B will be 38.4mm

Body B gives us the EXACT same image as body A, however we just don't see the edges of it (cropped)
Therefore, Doesn't that mean the PERSPECTIVE, has not changed, since the same lens is used. ONLY FOV has changed.
So an object in the center of the frame WILL appear to be the same distance to its background (equal perspective)

Scenario 2
On body A we have a 16-35L
On body B we have a 10-22 (eqiv 16-35)

Both now have an EQUAL FOV, but the perspective of BODY B will be Greater, that is, the object in the center of the frame will appear to have a greater distance to its background.


BUT, we're not done yet.....

Canon EF Lens Work III states, and i quote "...Perspective is related to angle of view, so even if the focal length is different for each particular lens, if the resulting angle is the same due to the difference in image size...the perspective will remain unchanged, too" from page 149

So Canon's definition, clearly states that in particular, Scenario 2 is wrong.

Who is right?

Scenario 1 is correct, except that you cannot measure FoV in mm, but let that pass.

Scenario 2 has me puzzled - are these two cameras shooting from the same position? If so, the perspective and relative sizes and distances are the same. The image formed by the cropper is smaller in absolute terms however. Therefore I assert that scenario 2 is false - the perspective is unchanged.

Canon's statement is nonsense. Perspective is independent of angle of view. It depends only on subject distance. However, the rest of their comment makes some sense, nearly, and conforms to my understanding.

I got lectured on this by Skip et al just last week. Let's see if any of what they said sunk in!

I think I have it now.
Canon says that "perspective is related to angle of view"
now, take a look at this diagram from EF lens work III pg 139
It shows the angle of view for each focal length.
On the page before this diagram, canon states "In particular, differences in focal length greatly change the range (angle of view), perspective, and depth of field of the subject being photographed."

So this means i am right. it also helps clarify the first quote i gave from canon.

lets try again.
we have 2 cameras on the same tripod (obviously not at the exact same time) in the same position.
the full frame has a FL of 135mm, which yields an angle of view of 18 degrees.
the crop (1.6x) has a FL of 85mm which yields an angle of view of 28 degrees.

the full frame camera WILL capture the same field of view BUT the angle of view is different so therefore perspective will be different, because "perspective is related to angle of view"

I hope this clears the discussion.

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This is how I would define these terms:

Perspective = appearance of the subject due to the position of the camera relative to the subject. Apparent perspective changes if the relative position of the camera is changed or if the focal length changes.

Field of View = the width and height of a scene captured by the camera dictated by both the focal length of the lens used and the distance of the camera relative to the scene.

As far as your specific discussion goes: I would argue that if two cameras captured the same image, their field of view and perspective must be the same, regardless of focal length and crop factor. Similarly, I would say that two pictures that appear the same, taken from the same camera at different distances to the subject with different focal lengths again have the same field of view and perspective. What I am saying is that field of view and perspective are attributes of the product of the camera setup, not inherantly built into the equipment itself. At least, that is my opinion.

Chiva wrote in post #4915332
I hope this clears the discussion.

It's clear enough, just wrong. I had it drummed into me last week that the only thing that affects perspective is distance from the subject.

Here's where I got educated:https://photography-on-the.net/forum/showthre​ad.php?t=449205
Salient quotes:
"The "distortion" usually attributed to a wide-angle lens usually has absolutley nothing to do with focal length, but instead has everything to do with the distance between the viewer (or camera) and the subject. The combinations of 10mm on a 40D and 16mm on a 5D will provide precisely the same angle of view and precisely the same image of the same subject from the same distance." - SkipD

"Perspective on two formats with the same distance to subject and same framing will have the exact same perspective, regardless of focal length. " - Jman13

"The 16mm on 'full-frame' and the 10mm on the APS-C ("1.6 crop") produce essentially identical angle of view, etc., and the image through the viewfinder of both rigs is virtually identical to the photographer (except for viewfinder image size, of course).

"In other words, both rigs would make virtually identical images from the same location relative to the subject." - SkipD

On the other hand, maybe I STILL have it wrong