Rethinking focal length conventions

Started 7 months ago | Discussions thread
J A C S
J A C S Forum Pro • Posts: 19,323
Re: 6%
1

Pixel Pooper wrote:

Phil A Martin wrote:

Pixel Pooper wrote:

My point is that a 43mm lens does not match the perspective of the human eye, it matches the perspective of an image viewed from a distance equal to the image diagonal. If you view your images from closer it might be 28mm that matches the perspective, and from a bit farther it might be 65mm. There is nothing special about 43mm except that it matches what was once considered "standard" viewing conditions.

So basically you are saying that the conventions of decades are wrong and that there is no such thing as a standard lens.

No, I'm saying that you, and many others misunderstood the conventions of decades and the meaning of a standard lens. A standard, or normal lens is one that produces a natural looking perspective under standard viewing conditions, which is when an image is viewed at a distance equal to its diagonal measurement. These are the same viewing conditions used by DOF calculators and in both cases the results are only correct when the viewing conditions are met.

The only study I have seen finds that the standard viewing distance corresponds to a considerable longer FL than the diagonal. Also, it depends on the size, i.e., it is not even proportional to the diagonal, it is something like 1.3 x diagonal + 25.3 cm. For larger prints, "normal" is 55-60cm. Nobody looks at their phone at 5 inches or so, BTW.

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