Focusing Screens - Telephoto Lenses

[David Mackay]

In my old film days I used the Canon 500mm mirror lens on an F1 body from time to time. With this lens, the standard focusing screen was not the best suited and so I would swap it for a Canon recommended alternative. Now, with older eyes and an EOS camera I am struggling to get pin sharp images from the 100-400 mm L series zoom at 400mm and am considering trying a different focusing screen to see whether or not this would help with manual focusing.

Does anyone have any views/experience on using alternative screens in this context?

Many thanks, David

[MX5]

Re: Focusing Screens - Telephoto Lenses

Ah 500mm mirror lenses ... Firstly have you tried viewfinder adjustment ... not the dial-in (which I'm nearly at the limit) but those slide in correction lenses? Or is it just that dark things aren't as bright as once they were? You can get alternative screens for some models ... there was a recent thread about this ... but AFAIK Canon don't do split screen focusing anymore (they may for the 1 series?). It's a variety of matt surfaces.

There's always live view ... if the situation allows.

[scarletti]

Re: Focusing Screens - Telephoto Lenses

Like you, my eyes are getting older and I find manual focussing difficult with the built in focussing screen on my 50D.
I tried a couple of different 3rd party split focussing screens and they certainly help with the focussing, BUT...

Whenever I use spot metering, which I frequently do when photographing birds from distance, it played havoc with the metering . Almost every shot was vastly overexposed (and I'm not talking a stop or 2). I even changed the focussing screen setting in the custom functions menu, but that made absolutely no difference.

I bought a different make after the exposure issues with the first, but that was exactly the same, so I have reverted to the original canon screen.