I grew accustomed to the notion that what one sees through a normal lens equates (or is close to) what can be seen with the naked eye (although that is not the "pure" definition of a normal lens, which is when the focal length and the sensor's diagonal are the same or close enough).
However, while playing with a zoom lens (on Canon APS-C, 1.6 crop) and keeping both eyes open, both views perfectly overlapped (and "merged") at 50mm (you get interesting effects when defocusing the lens at that stage, although you can't capture what you see).
That's a long stretch from what's considered normal on APS-C formats (between 25 and 35mm), so how could this be? Do full-frame DSLRs experience the same effect somewhere around 80mm?
Answer
What you are seeing is the effect of viewfinder magnification. For whatever reason (probably simply to make the numbers sound better), this spec is usually given for a 50mm lens, even on APS-C. The Canon 60D, for example, has a 0.95x magnification with a 50mm lens focused at infinity. And that's why around 50mm gives you the magic double-vision effect. There's more on this in Stan's helpful answer to What does "viewfinder magnification" mean?.
On full frame, the numbers are also given with a 50mm lens, so assuming a high decent magnification, you'll get the effect right around the normal length.
This is different from the idea that a normal lens produces output with a normal perspective, which should still hold true for around 30mm on an APS-C camera, assuming a typical viewing distance for the size of your prints. (Approximately arms' length for an 8x10, for example.)
No comments:
Post a Comment