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Friday, December 30, 2005

Not a Dumb Question

Q: Dumb Question? When you look through the "viewfinder" of an SLR, you see what the camera sees. When you look through the "viewfinder" of a rangefinder camera, you do not see exactly what the camera sees (parallax or something).

When you look through the back-side (full-screen) viewer (whatever it may be called) of a digital camera, do you see what the camera sees?

A: Right. The LCD screen reports what the sensor sees. Pretty exactly, too: most digital camera screens show pretty close to 100%, whereas many film SLR viewfinders show closer to 90% of what will be on the negative or transparency.

Q: But only in terms of area, not distortion, right? You just see less than what the camera sees but what you do see is exactly what you'll get?

A: Pretty much. There are slight differences, but nothing as bad as the parallax caused by using a separate viewfinder of any type. The main difference is that when you look through a modern SLR, you're seeing through the lens with the lens wide open. As you know, depth of field increases as you stop down, and lenses also get sharper and have fewer optical aberrations stopped down than at full aperture. So the rangefinder camera viewfinder suffers from parallax—slight differences in viewing angle—but it sees as the eye sees, in "pan focus," i.e.,
sharp front to back. If you're photographing in bright light and the camera is stopping down--say you're doing street photography on a bright day and shooting at ƒ/11--the rangefinder shows a more true image in that respect compared to, say, a 50mm ƒ/1.4 lens, which shows you the exact perspective through the viewfinder but much less depth of field than you'll get on the negative.

Or, as Roseanne Rosannadanna used to say, "it's always something."

The other differences in the image in an SLR viewfinder are usually very slight, and derive from the optical system of the mirror, the pentaprism, and the eyepiece. Some, naturally, are better than others.

I posted a tutorial on this subject a while back.

Posted by: MIKE JOHNSTON (thanks to BJ)


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