perspective vs. field of view

[back alley]

would i be correct in saying that a 35mm lens on a cropped sensor camera (say a 1.53 crop) would still have a 35mm perspective but a 53mm fov?

same for a 50 or a 28 etc...

i'm trying to determine why i might still like my favourite focal lengths even though the fov is different.

[BishT]

I've been wondering the same thing! Is a 28mm lens on an M8 a 37mm-equivalent or just a cropped 28?

[Nikkor AIS]

The best way I can describe it is like this. Think of the two formats like looking through two windows at the same tree. One of the windows is DX (cropped); the other is FX (24x36) full frame. Just because the tree occupies more space in the smaller window, it doesn't mean the tree is any closer. It just means there is less area around the tree compared to the big window (24x36).

[back alley]

Originally Posted by Nikkor AIS

The best way I can descibed it is like this . Think of the two formats like a looking through two windows at the same tree. One of the windows is Dx(cropped) the other is FX (24X36) full frame. Just because the tree occupies more space in the smaller window, it dosnt mean the tree is any closer. It just mean there is less area around the tree compared to the big window (24X36)

thank you obi wan...

[aizan]

no.

[back alley]

Originally Posted by aizan

no.

please don't mock my ignorance...

[kxl]

Originally Posted by back alley

please don't mock my ignorance...

Actually Joe, you may not have stated it quite as clearly, but what you're trying to say is correct. The other poster is wrong.

Assuming you stay rooted to the same spot and mount the rig onto a tripod -- your ZI and 35mm will have the same perspective as your R-D1 and the same lens. The FOV will be different, but the perspective is the same. You can easily test this -- setting it up as I described above, you can do 100% crop comparisons, and you will have identical images.

Focal length does NOT affect perspective; only distance to subject does.

[kxl]

Originally Posted by BishT

I've been wondering the same thing! Is a 28mm lens on an M8 a 37mm-equivalent or just a cropped 28?

A 28mm is a 28mm lens on full frame or any cropped sensor of any size, whether it be 1.25, 1.3, 1.5, 2.0 or whatever. Focal length is a physical property -- it does not change. .Only the field of view or angle of view changes.

Analogy -- if your height is 6.0 feet, it wouldn't matter if you are standing sitting or prone, you would still have a height of 6ft. What changes is what you can see from a standing, sitting or prone position.

[Brian Legge]

Yes - only the center of a lens that covers a full frame sensor is used on a cropped sensor body. It is similar to taking full frame image and either cropping it down to the center in Photoshop or when making a print.

[Roger Hicks]

Perspective and the illusion of depth are mental constructs drawing on many clues, and several of these clues are missing or different in photographs. Enlargement size and viewing distance change apparent perspective dramatically - and as apparent perspective is the only sort there is, there is no real future in making flat statements such as 'perspective depends solely on viewpoint'.

There are, after all, two viewpoints: the camera's viewpoint and the viewpoint when looking at the print, screen, or whatever. We have all experienced the 'magic window' effect, where the image looks uniquely three-dimensional, and this is tied closely to image size and viewing distance. It's something I have thought quite hard about, and discussed with others who have thought hard about it.There are two modules on the site about it: http://www.rogerandfrances.com/subsc...indow%201.html and http://www.rogerandfrances.com/subsc...ctive%201.html

Cheers,

R.

[marcr1230]

Focal length defines the relative size of near and distant objects in the image field
Sensor size defines the field of view or the crop from the above image

[mfogiel]

There are 3 aspects to this question:
- what will appear on the photo
- what will be the "perspective impression" i.e. has it been taken from close up or from far away
- what is the dof

If you take a shot with a 35mm lens on a film camera, then make a print, then take the scissors and cut away the borders, you will end up with what you get on your cropped sensor, but the "perspective" (i.e. distance from the subject) will be the same, and obviously also the dof will be the same (although on a digital sensor the dof is more shallow at the same f stop). If you will put an "equivalent" lens on your cropped camera (35mm/1.53=22.87mm )and will make the same picture from the same distance, the "perspective" will be the same (as the distance is the same), the coverage will be the same, but the dof will be bigger at parity of f stop,so you would have to open up your lens a bit in order to get identical result.

[Jeicob]

Wouldn't it make more sense to talk about DOF in the print and not the film/sensor plane?

[Nikkor AIS]

Keith, what part of the analogy of the tree and the windows is wrong?

Gregory

[FrankS]

This topic has been a can of worms in the past.

[Roger Hicks]

Originally Posted by mfogiel

There are 3 aspects to this question:
- what will appear on the photo
- what will be the "perspective impression" i.e. has it been taken from close up or from far away
- what is the dof

If you take a shot with a 35mm lens on a film camera, then make a print, then take the scissors and cut away the borders, you will end up with what you get on your cropped sensor, but the "perspective" (i.e. distance from the subject) will be the same, and obviously also the dof will be the same (although on a digital sensor the dof is more shallow at the same f stop). If you will put an "equivalent" lens on your cropped camera (35mm/1.53=22.87mm )and will make the same picture from the same distance, the "perspective" will be the same (as the distance is the same), the coverage will be the same, but the dof will be bigger at parity of f stop,so you would have to open up your lens a bit in order to get identical result.

Another way of looking at it is this:

You make a 20x30cm (8x12 inch) enlargement from the full frame, and physically remove the bit that isn't covered by the smaller sensor. Result: identical perspective, but less stuff around the edges. With a 1.5x multiplication factor, 16x24mm sensor, you'd have cut the picture down to roughly 13x20cm (5x8 inch).

If you then had a perfect photocopier, and could enlarge this print to 20x30cm, and looked at the new print from the same viewing distance as the old, the perspective wouldn't look the same.

Cheers,

R.

[Gumby]

Originally Posted by back alley

please don't mock my ignorance...

Originally Posted by FrankS

This topic has been a can of worms in the past.

so... I assume a good thing to do is ignore the mocking.

[fidget]

I haven't seen this discussed before. An interesting thread.
I can see how the perspective wouldn't change, simply a cropped image from that format we are comparing to, but...that would mean that my P&S digi at around 10mm fl should give a cropped 10mm perspective (as seen on a 35mm cam). It doesn't seem so.
Maybe I need to look a little closer at the pics for comparison.

[Finder]

Originally Posted by back alley

would i be correct in saying that a 35mm lens on a cropped sensor camera (say a 1.53 crop) would still have a 35mm perspective but a 53mm fov?

No. Perspective does change even though the relationship between foreground and background objects remain the same--that is just one aspect to perspective. Cropping and viewing distance has long been known to change perspective. This is not news.

You can go here for examples:

http://www.rangefinderforum.com/foru...t=90031&page=4

[Roger Hicks]

Originally Posted by FrankS

This topic has been a can of worms in the past.

Dear Frank,

True, and I've never seen why. Common experience: telephotos compress perspective, wide-angles stretch it. You can invoke all kinds of arguments about viewpoint, but the simple truth is that in order to get the same amount in, depending on the angle of coverage of the lens (different focal length or different film/sensor size) you stand closer or further away.

Likewise, you look at all prints of more or less the same size at more or less the same distance, regardless of what lens was used to take them. You don't look at an 8x10 taken with a 25mm lens at 25cm (10 inches) and at an 8x10 taken with a 250mm lens from a distance of 250 cm (eight foot four).

('You' as 'one', obviously, not 'you' as 'Frank')

Cheers,

R.

[Nikkor AIS]

Thanks photomoof. You saying I'm right is all the prize I need.

[Finder]

Which image has more depth? (Perspective is simply the apparent depth in an image.)

[ferider]

Say you take photo (A) with a perfect 35mm lens. Then take photo (B) from the same viewpoint of the same object with a 50mm lens. WRT perspective, the outcome will be identical compared to a (A) cropped 1.4x, and in print enlarged by the same factor.

Why you like the same lens when moving from one format to the next, Joe, must have to do with the lens, not any photographic parameter, like FOV, perspective, etc

Roland.

[Finder]

Originally Posted by Nikkor AIS

The best way I can describe it is like this. Think of the two formats like looking through two windows at the same tree. One of the windows is DX (cropped); the other is FX (24x36) full frame. Just because the tree occupies more space in the smaller window, it doesn't mean the tree is any closer. It just means there is less area around the tree compared to the big window (24x36).

This is wrong for two reasons.

1. You are not then enlarging the frames to be the same size.

2. Perspective is not simply the relationship between foreground and background object size. The entire frame is use to give depth.

[januaryman]

Originally Posted by Roger Hicks

Dear Frank,

True, and I've never seen why. Common experience: telephotos compress perspective, wide-angles stretch it.

Cheers,

R.

That's the first thing in this discussion that I've managed to understand and agree with. Thanks for that simple answer.