Manually focusing on the wrong "sharp edge"?

[Christian Skofteland]

On Mon, Jul 19, 2010 at 12:43:44PM -0700, Larry Colen wrote:
> 
> On Jul 19, 2010, at 12:41 PM, Bob W wrote:
> 
> > [...]
> >> I'm curious if other people have this problem when manually focusing, and
> >> what they do to fix it.
> >> 
> > 
> > I always found it easier to use a plain matte screen, depending on which
> > focal length I was using.
> 
> Please explain how focal length affects it.
> 
> Do you find the difference between in focus and out of focus too subtle on a wider lens?
> 

I think he might mean that for longer focal lengths you are generally using smaller maximum apertures and from what i understand and have observed, the split-image thingies tend to black out at anything above f4.  Really, a plain matte screen is the best tool for manually focusing in my opinion especially in low-light situations.

-- 

Christian
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