Lenses for photographing people...

Started Apr 8, 2013 | Discussions thread
clengman Senior Member • Posts: 1,964
Re: Lenses for photographing people...

OniMirage wrote:

clengman wrote:

OniMirage wrote:

clengman wrote:

OniMirage wrote:

clengman wrote:

Yup. I feel for you. It can be exhausting to be so, so wrong. Sorry if your brain hurts.

I like this link from the other thread,


I like it, too. But you didn't really read it did you? It has a lot to say about the differing perspective effects that result from varying subject distance, and how it's important to match the viewing distance to the perceived subject distance in order to create a "normal" viewing experience.

I like this quote from that article:

"The apparent expansions and compressions in depth are often called                perspective distortion, as if these effects are due to a distortion in the physical projection from the scene to the film plane. The effects occur, however, when the projections are geometrically correct."

This one too:

"If the viewer's eye is positioned at the picture's COP (center of projection), the image cast by the picture onto the retina matches the image that would be cast by the original scene."

It's similar to what I was trying to explain to you here:

"If you took the image captured by the camera and printed it and displayed it so that the print covered the same real angle of view in your field of vision as the angle of view represented in the print, it would look almost identical to your perception of the subject when you put your face all up in your subject's face. (I say almost identical because there are aspects of your perception resulting from parallax and binocular vision that obviously wouldn't be present.)"

and here:

"If you could freeze your entire field of vision, print it out, hang it on the wall and look at it, you would see that it looks very much like a photo taken with a very wide angle lens. Only the central few degrees of the image would be sharp, but the "distortion" would be the same."

For that same reason you ignore that they agreed with the affects wider angles give and the fact that 50mm and above tends to be more pleasing/ideal/correct

I didn't ignore anything. There's nothing I have said that contradicts anything in that article. I never said that wide angle shots don't often appear "distorted" (I don't like to use "distorted" here. I prefer to think of wide angle shots as having an unusual perspective.) I never said that wide focal lengths are ideal for head and shoulders portraits.

I had two quibbles with your first post that I responded to. One stemmed from your poor grasp of symbolic math. Secondly I disagree completely with your wording "It has only to do with rendering the subject accurately without distortion." As I've been trying to explain (and the article backs me up) 1. A rectilinear wide lens renders a scene accurately, 2. "Distortion" is subjective and  3. Perspective effects result from subject distance and angle of view.

"Perspective distortion" is not an inaccurate rendering of the scene and it's not due to any aberrant properties of wide lenses. The perspective effects that you notice are a result of a completely accurate rendering of a scene using a) a closer than normal subject distance or b) a wider than usual angle of view or both. I tried to point out that you can see the same perspective effects without a camera if you put your nose really close to an object, or if you really pay attention to the appearance of large objects at the periphery of your visual field.

If you had instead written "It has only to do with rendering the subject in a pleasing fashion with perspective that corresponds with that of comfortable interpersonal standing distance." (Or something like that...) I would have had nothing to argue about. (Except I still would have wondered why you thought the ideal portrait focal lengths were less than 50mm.)

I feel like this is getting repetitive. I can't really think of any better way to explain this or I would try. If you still don't understand, I guess I'm sorry I wasn't able to make it more clear.

How about I just leave this here then, it confirms without words, it animates it for you and you can come to your own conclusion.

Fine, it's a good illustration of how perspective changes as the camera to subject distance changes. It also confirms that you still don't really even understand what we're arguing about and that you completely missed the point of the article you linked to.

Now, back to the original argument. In this animation, perspective effects are only changed by changing camera to subject distance, and the only effect of changing focal length in this example is to change the angle of view.

In other terms (camera-subject distance in first frame) < (camera-subject distance in last frame) AND (angle of view in first frame) > (angle of view in last frame). These two facts along with fact that the viewing distance (or output magnification or however you want to think about it) is constant for the whole animation, account entirely for one's perception that in the first frame the cube appears to be stretched and in the last frame it appears to be compressed front to back.

A short focal length rectilinear lens does not distort. It creates a correct rectilinear projection of whatever scene you point it at.

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