RE: [APML] Focusing OM-1 - but what about the Nikon F2?

[John Mirtle <spampit@shaw.ca>]

Stuart,
	I can only comment based on my personal experience. With my Olympus
1-8 fine matte screen, the magnifier works great from 1200mm to 3900mm. Alan
is having good results at 820mm on his FS-102. When I started messing around
with my 180mm telephoto many years ago, I found that it was *not* accurate
enough. I also found that a knife edge was very touchy at such short focal
lengths, especially at f2.8. This is why I went with the 2 hole mask. I
would suspect that your 400mm would be in the same league - too fussy for a
magnifier but it shouldn't be too hard to use with a knife edge. The
magnifier seems to work best at long focal lengths and with slower focal
ratios.
	Of all the knife edge focusers I have tried, I agree with the other
comments - the Hutech unit rocks! At $20, the Lumicon option is sometimes
worth a shot - if you can figure out how to mechanically couple the
magnifier to your camera. For short FL's, there is something I have been
meaning to try. How about a 2 hole mask *and* a magnifier? It would be much
easier to see when the 2 star images overlap. Probably not as accurate as a
knife edge but it wouldn't cost much to try it out!

John Mirtle
Calgary, Ab. Canada

-----Original Message-----
From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org] On
Behalf Of Stuart Heggie
Sent: Friday, November 12, 2004 9:27 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Focusing OM-1 - but what about the Nikon F2?

Yes - the wisdom of John Mirtle is not to be discounted! John, do you think
it will work to focus
directly on the focus screen with the viewfinder removed from my Nikon F2?

Stuart


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