S3 viewfinder

[GiorgioNuvolari]

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Hello, I have recently had a chance to try an S3. When looking through the OVF, there is a fine grain visible across the frame. Is that normal, or should the frame be crystal clear?

Many thanks, GN

[TomLiles]

I think that's probably the grain of the matte focusing screen, Giorgio. If you look through film era camera viewfinders, you should see the same thing. It's a feature, for helping see the peak focus—digital era cameras have mostly dropped proper matte screens in the finder (for other perceived benefits), but not the S. It's another reason we all love it.

Edited April 30, 2021 by TomLiles

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[GiorgioNuvolari]

Thank you very much for the explanation, Tom! Much appreciates!

I am ready to enter the MF fold 🙂

best, GN

[tom0511]

it can also depend on the lens. With the zoom its a little "darker" and more visible compared to the faster lenses.

[mgrayson3]

Yep. I just looked through the S with 24 attached. stopping down to f/11 and hitting DoF preview made a very grainy focus screen visible.

There are interesting optical reasons for this effect. Remember - you are NOT looking at the subject. You are looking at a screen where the (hopefully in focus) incoming light rays are then scattered so that you can see some of them from each part of the screen. Think about ray tracing from your eye out to the subject. At the focal plane, each point should "see" a uniformly colored aperture disk corresponding to that point in the image. But the screen is not a perfect diffuser of light rays. It randomizes rays, but not perfectly. Now when stopped down, the aperture looks small as seen from the focal plane (sensor). So the diffusing light rays have a good chance to miss it. That causes the darker bits on the screen. Wide open, most of the diffused rays (or at least a reasonably constant percentage) hit the aperture circle, and so the screen image looks smooth.

This is the same reason the split screen focusing can go black on a slow lens. The split images come from the edges of the aperture window. Make a small aperture and you can miss the aperture window entirely.