Compression is Real

Started May 26, 2018 | Discussions
Great Bustard Forum Pro • Posts: 42,852
It is, but entirely due to position, not focal length.
6

JackM wrote:

The examples of "compression" (or, more appropriately, "perspective") below are due entirely to the position of the camera and positions of elements in the frame.  If one had used 100mm from the same position that the 400mm photo was taken from, the "compression" would have been the same, but the framing would have been 4x wider.

So, for sure, we can say that *for a given framing*, "compression" is a function of the focal length *for a given format*.

However, the problem with saying that "compression" is due to focal length without specifying both for a given framing and for a given format, is that people will incorrectly assume, for example, that a 50mm lens has a certain "compression" associated with it regardless of the sensor behind the lens (this same mistake is made with DOF as well).  And, to be clear, no, a 50mm lens on APS-C does not have the same "compression" as a 50mm lens on FF unless both photos are taken of the same scene from the same position, in which case they'll have a rather different framing.

In the end, it's much more simple to explain "compression" as the effect of perspective, and effect which is determined *entirely* by where the camera is located for a given scene, and the the framing is determined by the [equivalent] focal length for a given perspective.

100mm

164mm

271mm

312mm

400mm

Any questions?

Not a one.  You?

(unknown member) Senior Member • Posts: 2,498
Re: It is, but entirely due to position, not focal length.
2

True dat...

J.

Tom_N Forum Pro • Posts: 15,265
Re: Compression is Real
5

JackM wrote:

Wheatfield7 wrote:

JackM wrote

Any questions?

Did you figure this out on your own or did someone help you?

It’s my rebuttal to a number of recent pedantic articles and posts.

It's a flawed "rebuttal".

A lot of people claim that the focal length of the lens determines perspective, that a wide angle lens exaggerates features and a telephoto one compresses them.

That isn't so.  It is the camera-subject distance(s) that determine perspective.  Lens focal length just aids or hinders framing.

The error in the OP's argument is that his photos, taken with very different focal lengths, exhibit almost identical subject sizes and framings.  This implies that he changed the camera-subject distance(s) for every shot.  And it was that change in distances that produced the (perspective) "compression" in the more telephoto shots.

Nice try, but no cigar.

confused circle Senior Member • Posts: 1,932
Re: Compression is Real
4

Not only is it real, it is effectively created by the lenses you can access. Unless people feel like throwing away resolution and cropping like hell for no practical reason. Oh no, it's the distance! Guess what's going to dominate your distance choices. You aren't moving mountains, trees, buildings and the like. You aren't telling that group of players to repostion themselves for your convenience. You probably aren't soldering on a different sized image sensor in your body. So guess what, the lens you've slapped on is your biggest determining factor. And guess what you're going to do when that lens doesn't work consistently for your shooting. You're going to buy another focal length. Less likely that you will toss all your gear of the given sensor format just so you can get a totally new set to typically stand in a different spot for those shots you were having issues with.

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kiwi2
kiwi2 Veteran Member • Posts: 4,115
Re: Compression is Real
2

Tom_N wrote:

JackM wrote:

Wheatfield7 wrote:

JackM wrote

Any questions?

Did you figure this out on your own or did someone help you?

It’s my rebuttal to a number of recent pedantic articles and posts.

It's a flawed "rebuttal".

A lot of people claim that the focal length of the lens determines perspective, that a wide angle lens exaggerates features and a telephoto one compresses them.

That isn't so. It is the camera-subject distance(s) that determine perspective. Lens focal length just aids or hinders framing.

The error in the OP's argument is that his photos, taken with very different focal lengths, exhibit almost identical subject sizes and framings. This implies that he changed the camera-subject distance(s) for every shot. And it was that change in distances that produced the (perspective) "compression" in the more telephoto shots.

Nice try, but no cigar.

Nope, the OP has a valid point.

You need the longer focal length at the further distance. Otherwise the shot won't work relative to the frame.

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kiwi2
kiwi2 Veteran Member • Posts: 4,115
Exactly

confused circle wrote:

Not only is it real, it is effectively created by the lenses you can access. Unless people feel like throwing away resolution and cropping like hell for no practical reason. Oh no, it's the distance! Guess what's going to dominate your distance choices. You aren't moving mountains, trees, buildings and the like. You aren't telling that group of players to repostion themselves for your convenience. You probably aren't soldering on a different sized image sensor in your body. So guess what, the lens you've slapped on is your biggest determining factor.

Exactly.

Maintaining the foreground subject size in the frame (the baseball team in this case) with different focal lengths requires a change of distance.

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Big Stick Regular Member • Posts: 411
Re: Compression is Real

dwalby wrote:

JackM wrote:

400mm

Any questions?

are the skies really that beige color, or is that a "compression artifact"

Those are the famed Canon colors.

ajs jones New Member • Posts: 4
Re: Compression is Real
1

Compression is simply caused by moving the camera away  (=changing the perspective) - you simply choose to use a longer lens to record it  If you like the effect, you first choose a perspective (camera position) that alters the apparent relationship of the sizes of the objects in the scene to achieve the effect and THEN you choose a long lens.  If you use a shorter lens but a smaller sensor you will record exactly the same "compression" from the same place - same compression from a different lens, so it can;t be caused by the lens

PhozoKozmos
PhozoKozmos Senior Member • Posts: 1,389
Zero Compression: 100% Perspective

JackM wrote:

100mm

164mm

271mm

312mm

400mm

Any questions?

As smaller (foreground) subjects recede farther away than relatively much larger (background) subjects ...

the larger background subjects start to return to a more correct scale as the smaller foreground subjects

or

the smaller foreground subjects start to diminish to a more correct scale as the larger background subjects

this is why the moon at the horizon only looks large next to much smaller tiny real city skyline buildings farther away, than the moon held next to thumbsized toy cityscape snowglobe held up close to ones eyes

the moon doesn't change size, but only the perspective of small subjects seen up close or large subjects seen farther away

if one took a pic of your baseball team far away enough, they all look human sized in front of background buildings (church) = humans are tinier than buildings

  • ○~~~^~~~~
  • _____=^=___
  • ........[.■.]....

. = people, next to building

  • anyone can hold up the tiny eye of a needle close enough to fit the moon in the distance ... it's just a matter of perspective
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Max Iso
Max Iso Senior Member • Posts: 7,147
Re: Compression is Real

JackM wrote:

Wheatfield7 wrote:

JackM wrote

Any questions?

Did you figure this out on your own or did someone help you?

It’s my rebuttal to a number of recent pedantic articles and posts.

You have been put on Jeff Bezos' naughty list.

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confused circle Senior Member • Posts: 1,932
Re: Compression is Real

ajs jones wrote:

Compression is simply caused by moving the camera away (=changing the perspective) - you simply choose to use a longer lens to record it If you like the effect, you first choose a perspective (camera position) that alters the apparent relationship of the sizes of the objects in the scene to achieve the effect and THEN you choose a long lens. If you use a shorter lens but a smaller sensor you will record exactly the same "compression" from the same place - same compression from a different lens, so it can;t be caused by the lens

Distance is often determined by other factors, so distance is not the base cause for the perspective in a photo, it is what restricts your distance options that does it. The practical concern is where you physically can position the camera. In many cases, it is the lens forcing that. Other times it is the physical world of walls, streets, fences, etc. I really have right around zero luxury of choice when shooting something like candid 'street.' I can choose a lens, but I can't generally do much about my distance. If I can change distance, it's maybe just enough to get the framing for the lens I have on. So my distance is set by the lens and the time I have to frame and take a shot before the moment passes. Which is often next to none at all. I will, if able, step forward or back depending on what the lens makes me do, because I'm moving my feet before I'm digging for another lens (if I even have one). Which means the lens and the existence of a scene I want to capture is dictating my distance/compression, because I don't have time to let anything else influence the choice of distance.

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Mike CH Veteran Member • Posts: 9,631
Perspective is real
3

JackM wrote:

100mm

164mm

271mm

312mm

400mm

Any questions?

What exactly are you trying to show?

Your images show very nicely that perspective changes as you move, and that by changing focal length, you can maintain framing of your foreground subject.

Regards, Mike

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sybersitizen Forum Pro • Posts: 12,508
Re: Perspective
6

confused circle wrote:

ajs jones wrote:

Compression is simply caused by moving the camera away (=changing the perspective) - you simply choose to use a longer lens to record it If you like the effect, you first choose a perspective (camera position) that alters the apparent relationship of the sizes of the objects in the scene to achieve the effect and THEN you choose a long lens. If you use a shorter lens but a smaller sensor you will record exactly the same "compression" from the same place - same compression from a different lens, so it can;t be caused by the lens

Distance is often determined by other factors, so distance is not the base cause for the perspective in a photo ...

Yes it is.

it is what restricts your distance options that does it.

No it isn't.

What you're doing is misusing the term perspective. If you maintain the same physical relationship between the camera and subject and just change lenses, you are not changing perspective at all. Perspective remains the same. Every one of these images depicts the same perspective because the relationship between the camera and subject remains the same:

The magnification changes, and the framing changes, but the perspective doesn't change.

The practical concern is where you physically can position the camera. In many cases, it is the lens forcing that. Other times it is the physical world of walls, streets, fences, etc. I really have right around zero luxury of choice when shooting something like candid 'street.' I can choose a lens, but I can't generally do much about my distance. If I can change distance, it's maybe just enough to get the framing for the lens I have on. So my distance is set by the lens and the time I have to frame and take a shot before the moment passes. Which is often next to none at all. I will, if able, step forward or back depending on what the lens makes me do, because I'm moving my feet before I'm digging for another lens (if I even have one). Which means the lens and the existence of a scene I want to capture is dictating my distance/compression, because I don't have time to let anything else influence the choice of distance.

The two of you might find some common ground on the meaning of the word compression, but you can't get there by attempting to change the meaning of the word perspective.

confused circle Senior Member • Posts: 1,932
Re: Compression is Real
1

sybersitizen wrote:

confused circle wrote:

ajs jones wrote:

Compression is simply caused by moving the camera away (=changing the perspective) - you simply choose to use a longer lens to record it If you like the effect, you first choose a perspective (camera position) that alters the apparent relationship of the sizes of the objects in the scene to achieve the effect and THEN you choose a long lens. If you use a shorter lens but a smaller sensor you will record exactly the same "compression" from the same place - same compression from a different lens, so it can;t be caused by the lens

Distance is often determined by other factors, so distance is not the base cause for the perspective in a photo ...

Yes it is.

No, it isn't. A photograph is the end result of many decisions. It is usually the case that the distance is determined by another factor. Which means the perspective is then determined by that factor as well. You wish to speak as if distance can be selected at will, thereby creating whatever perspective one wishes in the photo. That is fantasy for most photos taken. The perspective is determined by what the photographer is able/allowed to do. There are countless situations in which the perspective will be determined by the fact that the photographer probably didn't want to die by trying to stand in a spot that would provide a different perspective. Self preservation determined the distance. Self preservation then constrained the perspective. It is wholly useless to ignore the fact that distance is not something one can choose at will at all times.

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sybersitizen Forum Pro • Posts: 12,508
Re: Perspective
5

confused circle wrote:

sybersitizen wrote:

confused circle wrote:

ajs jones wrote:

Compression is simply caused by moving the camera away (=changing the perspective) - you simply choose to use a longer lens to record it If you like the effect, you first choose a perspective (camera position) that alters the apparent relationship of the sizes of the objects in the scene to achieve the effect and THEN you choose a long lens. If you use a shorter lens but a smaller sensor you will record exactly the same "compression" from the same place - same compression from a different lens, so it can;t be caused by the lens

Distance is often determined by other factors, so distance is not the base cause for the perspective in a photo ...

Yes it is.

No, it isn't.

Yes it is.

A photograph is the end result of many decisions. It is usually the case that the distance is determined by another factor. Which means the perspective is then determined by that factor as well. You wish to speak as if distance can be selected at will, thereby creating whatever perspective one wishes in the photo. That is fantasy for most photos taken. The perspective is determined by what the photographer is able/allowed to do. There are countless situations in which the perspective will be determined by the fact that the photographer probably didn't want to die by trying to stand in a spot that would provide a different perspective. Self preservation determined the distance. Self preservation then constrained the perspective. It is wholly useless to ignore the fact that distance is not something one can choose at will at all times.

You are just repeatedly misusing the term perspective.

A more intuitive synonym for perspective is point of view. A camera exists in a position in space (usually relative to a reference point on planet Earth). It's also oriented toward some other point where the subject is. The only way in which you can change the point of view or perspective is to move the camera to a different point in space (up, down, left, right, forward, or back) and/or change its orientation toward a different point.

If instead you maintain the same physical relationship between the camera and subject and just change lenses, you are not changing point of view or perspective at all. They remain the same. Every one of these images depicts the same perspective because the relationship between the camera and subject remains the same:

The magnification changes, and the framing changes, but the perspective doesn't change.

Tom_N Forum Pro • Posts: 15,265
Re: Compression is Real
3

confused circle wrote:

sybersitizen wrote:

confused circle wrote:

Distance is often determined by other factors, so distance is not the base cause for the perspective in a photo ...

Yes it is.

No, it isn't. A photograph is the end result of many decisions. It is usually the case that the distance is determined by another factor. Which means the perspective is then determined by that factor as well. You wish to speak as if distance can be selected at will, thereby creating whatever perspective one wishes in the photo. That is fantasy for most photos taken.

Perspective is a function of the camera-subject distance(s).  As far as physics and optics are concerned, it doesn't matter whether you have full freedom to pick those distances.  A camera will not deliver the same perspective at 12 inches as at 1200 feet just because its user wants to pretend that changing focal lengths changes perspective.

Self preservation determined the distance. Self preservation then constrained the perspective. It is wholly useless to ignore the fact that distance is not something one can choose at will at all times.

The definition of perspective does not say that you can always choose any distance.  But by the same token, you don't get to redefine what affects perspective, just because some distances (and therefore some perspectives) might have been unavailable to you.

(unknown member) Senior Member • Posts: 2,498
This will explain your confusion...
Gerry Winterbourne Forum Pro • Posts: 15,457
Re: Compression is Real
3

confused circle wrote:

ajs jones wrote:

Compression is simply caused by moving the camera away ...

Distance is often determined by other factors, so distance is not the base cause for the perspective in a photo, it is what restricts your distance options that does it.

You have this the wrong way round. Perspective is the way the relative sizes of things depends on their distance from a viewpoint, and only on that. For any given viewpoint perspective is always the same and depends only on that viewpoint.

A photographer may want to frame his picture in a particular way and therefore choose a particular viewpoint. But the perspective from that viewpoint is determined entirely by the viewpoint itself. It is predetermined by the spatial relationship between the viewpoint and the scene.

To put it another way: in a location there is an infinite number of perspectives; each of those is determined by viewpoint; a photographer can choose one of those viewpoints and that is his choice; but once the choice is made perspective depends on the viewpoint.

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fatdeeman Regular Member • Posts: 213
Re: Compression is Real
2

kiwi2 wrote:

Tom_N wrote:

JackM wrote:

Wheatfield7 wrote:

JackM wrote

Any questions?

Did you figure this out on your own or did someone help you?

It’s my rebuttal to a number of recent pedantic articles and posts.

It's a flawed "rebuttal".

A lot of people claim that the focal length of the lens determines perspective, that a wide angle lens exaggerates features and a telephoto one compresses them.

That isn't so. It is the camera-subject distance(s) that determine perspective. Lens focal length just aids or hinders framing.

The error in the OP's argument is that his photos, taken with very different focal lengths, exhibit almost identical subject sizes and framings. This implies that he changed the camera-subject distance(s) for every shot. And it was that change in distances that produced the (perspective) "compression" in the more telephoto shots.

Nice try, but no cigar.

Nope, the OP has a valid point.

You need the longer focal length at the further distance. Otherwise the shot won't work relative to the frame.

But that means his priority is the framing and the perspective is just a consequence. All the OP has done is confirm the article is correct and confirm his own misunderstanding.

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Art Jacks Senior Member • Posts: 2,959
Re: Compression is Real
1

My examples prepared for my wife’s photography class.

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