Is it a linear progression between 90mm and 150mm?

[Daniel Casper Lohenstein]

This is incorrect. Perspective is only changed by positioning of the camera. This misconception comes from the inherent moving of the camera when switching lenses to match framing/composition of the lens prior. If you compose a little loose with a wider lens and then crop later, you still have the same perspective regardless.

This is a very special quibble that has been repeated over and over for many years, because it can be found in textbooks where the pipe-smoking authors set their cameras on tripods and make hypothetical considerations while drinking tea from a thermos.

What Corran is describing is only one single and very rare special case of perspective representation, namely the modification of the focal length and thus of the image section while the point of view next to the car remains the same. Of course Corran is right, but this special case is completely irrelevant for serious pictorial photography, where you have to use your feet to find an adequate perspective.

Every photographer who screws on a short focal length lens instead of a normal lens will confirm the experience that, in order to achieve a constant object size, he or she moves closer to the object. This changes the visual penetration of the space, and thus the view from the eye of the objects distributed in the space changes. "Perspective" comes from "perspicere", and that means: "look closely, take a closer look, examine, sample", not only "look inside". There is always an object included that is looked at more closely. Albrecht Dürer already recognized this, cf. http://public.media.smithsonianmag.c...rspective1.jpg

Thus, lateral objects are no longer seen frontally from the front, but more from the side, which emphasizes the depth-space extension, compared to objects seen frontally. Take some cacti in in a landscape with mountain on the horizon: if you want them to stay the same size, you have to get closer with a short focal length, which is why you see them more from below, perhaps, making them appear larger relative to the mountains in the background. While a long focal length emphasizes a more real ratio between cacti and mountains, cf. Andreas Feininger.

Perspective is unthinkable without perspective origo, and the chosen perspective origo is the essential characteristic of the photographic author's point of view. The way he sees things, he valorizes or devalues them, relates them. And a short focal length thereby emphasizes the difference between front and back, while a long focal length creates pure frontality.

[afotandolaciudad]

If you want to compose the exact picture on the ground glass and never ever crop the negative, the use of close up lenses may be interesting.
You can carry three lenses and 1 or 2 good achromatic lenses. For example: 90mm, 150mm and 300mm with 2 diopter close up give you (aprox.) 75mm, 115mm and 190mm.

[Corran]

Of course Corran is right

That's all that needed said. A good number of photographers think perspective is a property of the lens, and one can see the abuse of wide-angle lenses frequently online by hobbyist photographers everywhere. The (correct) distinction between focal length and "perspective" as a property of camera location (get closer) should not be dismissed as mere textbook knowledge.

PS: When I started photography I also thought "wide-angle = wider perspective" or whatever too, and shot an awful lot of mediocre images with a 14mm lens on my digital camera. It wasn't until I started to understand that I needed to get closer and pay attention to the real perspective as presented by my location (and camera) and not rely on focal length that I began making good wide-angle images.

[Drew Wiley]

A lot depends on the objective. With a personal landscape shot, I'm apt to compose it with whatever best-fit lens I happen to have along, from whatever spot simply feels the best. With a commercial architectural shot, the client might very well dictate what belongs in the confines of the image frame; and the amount of working space available behind it will determine the lens choice. I always scouted out architectural jobs in advance with respect to lighting and lens requirements. Studio work is different still because things can be arranged.

[neil poulsen]

This is incorrect. Perspective is only changed by positioning of the camera. This misconception comes from the inherent moving of the camera when switching lenses to match framing/composition of the lens prior. If you compose a little loose with a wider lens and then crop later, you still have the same perspective regardless.

I think that it's important to treat framing independently from perspective, the latter being camera position. In approaching a composition, I like to explore different camera positions without considering framing. One for the relationships of different elements in the composition to each other, and those relationships change as camera position changes.

Once I've decided on camera position, only then do I use a cut-out card to determine the strongest framing. One reason I like multiple lenses, is that once I've decided on framing, I can select the lens that best fills the format, yet which retains all the elements within the frame.

[Michael R]

All you’re doing here is confirming the facts, I think, and in my opinion they constitute more than a “quibble”. They are pretty fundamental and every beginning photographer should be aware of them to avoid aimlessly moving around and changing lenses without an understanding of how these things alter the picture either individually or in combination. Of course there are rendering subtleties, the imperfections of lenses etc. But I think it is good for people to understand at least directionally what is going on. That is:

Moving the camera changes perspective. Changing the focal length of the lens is a crop factor.

The photographer is free to use these two properties together to control near-far relationships, perspective, relative sizes of objects etc.

This is a very special quibble that has been repeated over and over for many years, because it can be found in textbooks where the pipe-smoking authors set their cameras on tripods and make hypothetical considerations while drinking tea from a thermos.

What Corran is describing is only one single and very rare special case of perspective representation, namely the modification of the focal length and thus of the image section while the point of view next to the car remains the same. Of course Corran is right, but this special case is completely irrelevant for serious pictorial photography, where you have to use your feet to find an adequate perspective.

Every photographer who screws on a short focal length lens instead of a normal lens will confirm the experience that, in order to achieve a constant object size, he or she moves closer to the object. This changes the visual penetration of the space, and thus the view from the eye of the objects distributed in the space changes. "Perspective" comes from "perspicere", and that means: "look closely, take a closer look, examine, sample", not only "look inside". There is always an object included that is looked at more closely. Albrecht Dürer already recognized this, cf. http://public.media.smithsonianmag.c...rspective1.jpg

Thus, lateral objects are no longer seen frontally from the front, but more from the side, which emphasizes the depth-space extension, compared to objects seen frontally. Take some cacti in in a landscape with mountain on the horizon: if you want them to stay the same size, you have to get closer with a short focal length, which is why you see them more from below, perhaps, making them appear larger relative to the mountains in the background. While a long focal length emphasizes a more real ratio between cacti and mountains, cf. Andreas Feininger.

Perspective is unthinkable without perspective origo, and the chosen perspective origo is the essential characteristic of the photographic author's point of view. The way he sees things, he valorizes or devalues them, relates them. And a short focal length thereby emphasizes the difference between front and back, while a long focal length creates pure frontality.

[Drew Wiley]

I've never used a cutout card in my life.

[Salmo22]

Just the notion of cropping from a wider image instead of framing with a longer focal length lens. Nice in theory or conservatively applied, but not always practical in terms of real-world composition. Of course, the more ridiculous comment that comes up is when someone tells you to just walk closer to the subject. Yeah, with a tree in the way, or a cliff a few steps ahead, or a 7000 ft deep canyon in between, or the angle of view totally changed from the preferred position. Just speaking in principle. Don 't take it personal. My posts aren't necessarily rebuttals.

As a follow-up to your comment, in the scene below there is water (over 6' deep) on the other side of this concrete buttress. There was no moving the tripod to get closer to the next buttress without going for a swim. The only option I had was to change lenses until I found the focal length that helped me achieve the composition I had envisioned. While I could not get it 100% perfect, it is very close. In my opinion, a much better result than if I'd gone wide and cropped it tighter in the darkroom. My father, a commercial photographer, taught me to get my desired composition as close as possible "in camera". It is a practice I try to follow. Zooming with my feet rarely works well for me. Maybe this is nothing more than a creative mental block my father placed long ago

[Michael R]

I've never used a cutout card in my life.

It can be a pretty useful tool, especially given it costs virtually nothing, so a lot of bang for your buck. And it isn’t just useful for “beginners” or as a teaching tool. I know of a few highly accomplished artists who use them. They are useful not only for getting a sense of focal length per se, but also for general composition and framing, what to include/exclude etc. This can be handy for dealing with complex compositions and/or dense/cluttered subject matter, or even for preliminary worth it/not worth decisions before setting up a camera.

Of course I’m not suggesting YOU need one, but generalizing.

[Daniel Casper Lohenstein]

YES.

However, I would like to mention a particular aspect that becomes effective during cropping or amplification.

Suppose I see a landscape at 300mm for 4x5. Then I see things rather frontally. If I now look at the same landscape with a 90mm on the same camera position, without performing even a shift, tilt, rise, swing, then I will see more things in the picture. These things are on all four sides of the original 300mm image. Of course, the center frame of the picture with the 90mm lens is the same as that of the 300mm lens. But there are a few more objects on the sides, on the ground, and in the sky.

The perspective remains the same, but I don't see these objects from the front, but from above or below or from the side, because they aren't in the center of the image, where the vanishing point of the perspective construction normally lies. And by seeing them from the side, I see them differently than the objects in the center of the image, which I see from the front, as with the 300mm. Harvey Shaman describes this very clearly in "The View Camera. Operations and Techniques". Thats why we create an impression of spatial depth by lowering the front standard or rising the back standard ...

This is a very interesting discussion here.

All you’re doing here is confirming the facts, I think, and in my opinion they constitute more than a “quibble”. They are pretty fundamental and every beginning photographer should be aware of them to avoid aimlessly moving around and changing lenses without an understanding of how these things alter the picture either individually or in combination. Of course there are rendering subtleties, the imperfections of lenses etc. But I think it is good for people to understand at least directionally what is going on. That is:

Moving the camera changes perspective. Changing the focal length of the lens is a crop factor.

The photographer is free to use these two properties together to control near-far relationships, perspective, relative sizes of objects etc.