Originally Posted by
Jerry Fusselman
Gregory,
You bring up several issues.
You, and several others, wonder, Does any 35mm-portrait photographer really think that a 300mm focal length can be clearly superior to 85mm? I never said most 35mm portrait shooters think so. My task is only to show that some do.
Please recall from my initial post that a 14-foot shooting distance corresponds to a 35mm photographer's 300mm lens, and a 4-foot shooting distance corresponds to an 85mm lens. (More accurately, the numbers are 14.32 and 4.06 feet.) For the upcoming quote, please remember 14 feet and 4 feet as distances that determine two quite different perspectives.
For my demonstration about 300mm lenses for 35mm portrait photographers, I start with quotes from a photo.net article called "Portrait Photography":
And here are two examples from the photo.net thread "300f4 as a portrait lens":
Even if someone has signed affidavits of one thousand 35mm portrait pros who despise 300mm lenses, even if so, I have now established all that I want to about 300mm for the purpose of my questions.
Actually, what other photographers do matters very little to me when their "common knowledge" leads to inferior practice. And I generally like my images more than other photographers', so why should I copy others? My attitude is not that unusual, is it? (Galen Rowell's wife, Barbara, generally liked her own images best at locations also photographed by her husband.)
Then why am I personally interested in 300mm? Well, I noticed in my own 35mm portrait shots that my 300mm images seemed especially pleasing. I had used that huge, heavy lens almost by accident---only to keep my equipment safe and out of the water for a special location on a Lake Michigan beach. My sitter and I thought the resulting perspective strikingly good compared to the various shorter focal lengths I used for a couple thousand other shots. The 300mm images really seemed somehow more beautiful and glamourous. That is how I got the idea of trying for more resolution in a larger format---but with that same perspective!
Some may say, well, 300mm shots (on 35mm) look better just because you had extra control over the background with the longer lens. But my answer is that that is a major benefit of the longer perspective, so if the better background is the 35mm pro's reason for the longer lens, then I probably want that with large format too.
You admit, "The longer lens also makes it easier to throw the background out of focus, making the subject's face standout from any distracting elements. In this regard, the 300mm is often used on location, like the beach."
The longer lens allows more control over what parts of the background show, but it does not materially affect depth of field if you hold image magnification and f/stop constant, as I explained earlier in this thread. I hope you agree with this. Many posters think focal length materially affects depth of field in this context, but it doesn't. Remember, we are talking about head-and-shoulders portraits in a given format, so we take magnification as given. It is easy to check the numbers if you doubt it: Focal length has no material affect on depth of field for this image.
First you assert, "When a longer focal length lens is used, less of the scene is included, but perspective remains unchanged," and several posters in this thread agree with you, but later you quote Stroebel, who says the exact opposite: "It is not correct, however, to say that focal length has no effect on perspective." I cannot tell which position you agree with, but personally, I agree with Stroebel.
Stroebel defines the terms weak perspective and strong perspective, but he does not mean any value judgement by the terms. The fact that a longer focal length gives you a weaker perspective does not mean longer focal lengths necessarily give inferior results.
This leads to the question, Does it makes any sense to choose your perspective first if you want an excellent result? Many posters on this thread seem to say "no" when it comes to portraits. And your post contradicts itself on this issue. First you say, "a photographer can use ANY camera and ANY lens to make a portrait. I cannot emphasize this observation enough." This is the lens-first, framing-second, perspective-last school. You say one should choose the lens, "ANY lens", choose the desired image size, and then accept the resulting perspective.
My preferred alternative to this thinking can be called the perspective-first school. Here, you choose the lens only after deciding on your desired perspective. These two schools are opposites from the standpoint of perspective, because one has your perspective chosen last, and the other has it chosen first. It is crucial to see the difference.
You started by endorsing school #1, the perspective-last school, but your post later inexplicably shifts to endorse school #2 (the perspective-first school) by saying, "Stroebel goes on to say that it's best to select camera position first based on the perspective desired, and then choose the lens focal length that will produce the appropriate image size. (I agree with this assertion.)" You go back to school #1 in your closing paragraph of your part 2 (which ironically rejects using math immediately after listing more than 30 equations).
This paragraph from Stroebel (p. 130), even though you cited part of it, clarifies what I just tried to say:
"Inexperienced photographers usually select the camera position on the basis of factors other than perspective. The tendency is to adjust the distance between the camera and the subject to obtain the desired image size and angle of view or to select the most convenient location for the camera without giving consideration to the perspective. . . . Professional photographers learn to control perspective to obtain the desired effect. To do this, it is first necessary for the photographer to be aware of the subtle as well as obvious perspective effects. The camera position is then selected on the basis of the perspective desired, and finally, the focal length lens that will produce the appropirate image size is used."
Do you see? Your endorsment of "ANY lens" (your caps) matches the way inexperienced photographers do it. The fully professional way is to think about perspective first, and only after satisfying your perspective goals do you choose your focal length. Someone asked, "Why all the math?"---the answer is simply that I want to see how to achieve a certain perspective.
Why discuss angle of view? Actually, I think angle of view should be ignored, but you wrote this: "It's my impression that you may have confused angle of view – what the lens "sees" (or the angle of subject area projected on the film) – with perspective – the distance from subject to the lens rear nodal plane, or "v" in commonly used lens formulas."
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The right answer if you want to match u as you change formats, as readers of my paper should be able to verify, was given in my original post: An 85mm lens in 35mm (assuming an 8x10 target print so the image size is 24mm by 30mm) corresponds to 300mm in 4x5 and 480mm in 8x10. If you like a significantly weaker perspective than this, then you have to go to significantly longer than these focal lengths.
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