Diopter settings?

Hi folks,

Got a 1D MK III 6 or 7 months ago. Set my diopters setting once and never thought about it. All was fine.

This weekend, with a new lens, noticed things were out of focus. So I immediately thought the lens was misfocusing. however, about three clicks of the diopter wheel and all was good and images were sharp.

Today, I checked another lens or two and the lens that caused me to make the diopter change and it needed to be reset back to the old setting.

So, can diopter settings drift? Can they be different for different lenses?

I assume, correct me if I am wrong, that diopter settings are tied to the mirror assembly. If so, could the mirror be shifting around?

Appreciate some insight as I want to watch what might be happening while I am under warranty.

Thanks.

~Bob

I have been told that the diopter setting will only effect having the AF points in or out of focus.

The whole image focus through the view finder changes with a change in diopter settings.

~Bob

The AF points and viewfinder LCD should be sharp, that's when the diopter is set correctly. If the image is still blurry (but the points and LCD are sharp) then the focussing screen could be misaligned and would need shimming.

To test it use a lens with a maximum aperture of f/2.8 (I think that's the highest the standard screens can display) to help differentiate between in and out of focus. Mount the camera on a tripod with mirror lock-up and a remote release (to minimise camera shake) and using the centre focus point (for greatest accuracy) take a photo at f/2.8 (preferably of something that's easy to tell if it's in focus or not like some text). If the image is in focus so should the view through the viewfinder, otherwise it needs shimming. If the image is out of focus then micro adjust the lens until it's spot on and try again.

Thanks, but maybe I did not explain myself adequately.

Images have always been sharp. With any lens. But recently I had to readjust the diopter setting for the image in the viewfinder to be sharp. And now had to readjust it back to keep it sharp.

So, the more I think through this, the lens has nothing to do with this. Must be either a mirror or, as you say, focusing screen that might be moving. Nothing else I can think of unless what ever is connected to the diopter wheel could be loose.

Anyone know what the diopter wheel is connected to mechanically to change the setting? That could be what is loose.

~Bob

It was, probably, accidently turned.

The diopter adjustment has nothing to do with the image. It is only to adjust the focal distance to the focus screen. I have found that it is easiest to adjust when the lens is removed. Focus until the boxes on the focus screen are sharpest. If it is changing from lens to lens there is something else going on like a loose screen. It should not change and it does not matter what lens is on.

bohdank wrote in post #10995419
It was, probably, accidently turned.

Not at all. It sits protected under the eyecup and was exactly where i had set it originally. Can't get to it without removing the eyecup and I only do that when I adjust the diopter - very rarely.

Now, if it were my G9, I would agree with you.

~Bob

Still trying to find out what it does when you turn the dial. Move something mechanically? Googling it now.

Bob,

I practically need a tool to adjust the diopter on my 7D. The 5D (well broken in) is another story. It moves much easier and is prone to moving a couple clicks now and then. My guess is from moving in and out of the pretty snug gear bag it lives in.

Funny though, you think it's the lens, I instantly suspect my EYEBALLS!!!

dave

I do believe it just moves some optical elements in the viewfinder, similar to how a lens focusses. It doesn't move the mirror or focussing screen and the chances of them moving around are pretty slim, the optics in the viewfinder could be loose but I wouldn't have thought that's very likely either.

Try shooting at your lenses maximum aperture to make sure it's not focus shifting (where it's in focus at it's largest aperture which all lenses focus at, but when stopped down to take the photo the focus shifts). If you've MA'd your lens there's a chance you did it at a smaller aperture so the lens actually shifts in to focus instead of out.