Perspective (yet again, sorry!)

Started 2 months ago | Discussions thread
J A C S Forum Pro • Posts: 14,470
Re: books are frequenty wrong

tko wrote:

Perspective on viewing a photograph

The perspective obtained on viewing a print - sometimes termed the apparent perspective - depends, firstly, on the relative sizes of objects in the print - and hence on the perspective obtained in the negative on taking the photograph - and, secondly, on the distance at which the print is viewed.

Correct perspective is said to be obtained when a print is viewed in such a way that the apparent relation between objects as to their size, position, etc., is the same as in the original scene. This is achieved when the print is viewed at such a distance that it subtends at the eye the same angle as was subtended by the original scene at the lens. The eye will then be at the centre of perspective of the print, just as, at the moment of taking, the lens was at the centre of perspective of the scene.

Unfortunately, this is wrong. The viewing point for a photo is forever fixed at the point from where the photo was taken. In the 3D world, moving closer and farther changes the relative sizes of objects that aren't the same distance from the lens. But once captured in a photo, the relative sizes are forever fixed.

Take the classic example of a portrait taken close up. The features are exaggerated. Try as hard as you can, no amount of moving the photo back and forth will alter this exaggeration.

There is nothing in what you call wrong, saying that the features can become less exaggerated with the viewing distance.

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