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[OM] Re: OM focus screen question

Subject: [OM] Re: OM focus screen question
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Tue, 08 Jan 2008 07:58:09 -0500
I don't have any tips for you but will just comment that the reason for 
the focusing difficulty is that, even as close as 12 feet, the DOF for a 
24/2 is quite large, extending from 8.5 to 20.7 feet.  Even cutting the 
conventional 8X CoC in half to allow a 16X enlargement the DOF still 
runs from 9.9 to 15.2 feet.

Well, maybe this does count as a tip.  If you're actually shooting not 
at f/2 but at a middle aperture like f/5.6 or f/8 the DOF is so great 
you might just as well set the lens at the hyperfocal distance and 
forget about focusing.  The hyperfocal distance at f/5.6 is 10.2 feet, 
f/8 is 7.2 feet and f/11 is 5.2 feet.  You can literally just set it and 
forget it but if you're going to shoot like that all night I find it 
useful to tape the focus ring in place.

The only other thing that I can think of is to pick an object about the 
same distance away as your subject but one which may be more brightly 
lit and has stronger contrast.  Given the wide DOF, the actual distance 
to the focusing target vs. the real target need only be in the ballpark.

Chuck Norcutt

Amin Sabet wrote:
> Well I just mounted the OM 24/2 for the first time, and it's tough for
> me to get a sense of focus with this lens compared to the 50,
> especially with somewhat more distant objects in low light.  Not such
> a big deal I suppose, since I'll probably zone focus more often than
> not when quick focusing is necessary.  Anyone have any tricks to share
> for focusing this lens at f/2 on subjects12-20 feet away =) ?
> 
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