50mm "Normal" Lens... Ok, but "Normal" on FF or APS-C Sensor?

Started Nov 10, 2012 | Discussions thread
KLO82 Contributing Member • Posts: 956
Re: Not the 50mm myth again. That one is tough to kill!

Here are two very good posts which explains "normal lens" and telephoto compression/ wide angle distortion very nicely:



Marc Sabatella wrote:

Normal focal length has everything to do with angle of view. Indeed, it's the only thing thing that defines what normal is. There were a number of incorrect statements and misunderstandings in your earlier posts, but rather than address those individually, let me just start here.

A lens is "normal" on a given camera if its angle of view matches the angle subtended by a typical print when viewed fro a typical distance - meaning the definition is at least somewhat subjective. But contrary to your earlier statement, it absolutely depends on making a print, or displaying an image in some form where we can measure the angle of view.*


perspective has nothing to do with focal length or angle view. Perspective is indeed dependent on shooting position and shooting position only. Telephoto compression arises for a simple reason. The eye/brain sees an image of an object that appears to be a certain size. It doesn't know the focal length used, so if he sees an onject rendered relatively big in the frame, he tends tends to assume the photographer was relatively close to the object. If the photographer was actually relatively far away but shooting telephoto, then the viewer of the imsge will see the "wrong" perspective. The imge will ahve the perspective that results from far away, which will mislead the viewer who thinks the photographer was relatively close. The incorrect perspective will cause the viewer to misread distances between objects, relative sizes of objects, etc. It's an optical illusion,but a really good one.

Mark Ransomwrote:

Take the classic sports shot of a player with the crowd behind him. It looks like the camera was maybe 20 feet from the player, because that's how close you would be if you saw him at that scale in real life. Then you look at the crowd behind him and realize that they look too close. This happens no matter what size print it is, or how closely you hold it.

Reply from Marc Sabatella:

Have you tried viewing a 4x6" print from, say, 10 feet away? If you hold the photo far enough away that the player looks the same size he did from the shooting position, then the crowd will also be rendered that the same size they appeared from the shooting position, and I guarantee the perspective distortion will go away. It is physically impossible for it to be otherwise. Perspective is not subjective.

Marc Ransom wrote: Likewise the distortion of facial features with a close-up using a wide-angle lens. It looks funny regardless of the print size or distance.

Reply from Marc Sabatella: Again, just not true. But you'd probably have to hold the picture closer than your eyes can focus in order to make the effect go away.

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