Manually focusing on the wrong "sharp edge"?

Larry Colen lrc at
Tue Jul 20 02:53:49 EDT 2010

On Jul 19, 2010, at 6:36 PM, Doug Brewer wrote:

> Larry Colen wrote:
>> I was photographing a friend playing in a small club in Capitola the other night. When I reviewed my photos, I found that an awful lot of them were focused on sharp edges in front of the musician:
>> The tip jar, drum kit, microphone etc.
>> I understand how this happens with autofocus. The camera is too stupid to know what to focus on and focuses on the sharp edge.  What I don't understand is why this happens on manual focus. *I* should know better.
>> One challenge that I have in low light is actually seeing the line of the split prism to try and line that up on the musician. Especially musicians that tend to move around a lot.  As such, I may rely a lot more on the microprism ring, and wonder if I just focus until I see whatever is in that ring come into focus, and not notice that it's not actually the subject that I'm trying to photograph.  More a case of my brain saying "something is sharp, press the shutter".
>> I'm curious if other people have this problem when manually focusing, and what they do to fix it.
>> I got what I thought was an amusing compliment on my dancing that night.  I had a rather nice slow blues dance with an attractive young lady. Afterwards, she said in a rather husky voice "I need a cigarette". Unfortunately, she was married. Even worse, her husband doesn't share.
>> I did get a couple shots of the lead singer which turned out pretty well:
>> In the second one Amy Lou isn't as sharp as I'd like,  but I do like the way the composition worked out with Gary (the bass player) in the background.
>> --
>> Larry Colen lrc at sent from i4est
> Never understood the fascination with split prisms. They're clunky and self-limiting. Give me a plain matte any day for manual focus.

When I got my K100 I couldn't manually focus with it to save my soul. When I got the katzeye, it was like growing back a missing limb.

> I suspect you're shooting yourself in the foot here, Larry, by trying to use the split prism and recomposing at f/1.4. You don't have any wiggle room shooting with such a narrow DOF, and I think this could go a long way toward explaining why your focus is off too often. Stop the lens down a couple clicks. This will help with the focus and will also make the photos look like they were taken at night in a club, instead of afternoon in the park.

At ISO 6400, and missing more photos due to subject motion blur than bad focus, I'd end up with photos with depth of field, but so much noise, or motion blur, you wouldn't see anything.

Most of the screen is matte anyways, so I can try using that section more anyways. The focus of my interest is rarely dead center anyways.  Most of the situations where I shoot the split prism gets me a lot closer than I could with a matte screen. I know this because I'll focus using the matte portion of the screen, and check it with the split prism.

Since most of my photography seems to be with fast lenses 77mm or shorter, I rarely have any problem with the dark center syndrome with the split prism. 

> Also: Relax. It's only photography.

That it is, but I'm still trying to learn techniques to get better at it.  
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Larry Colen lrc at sent from i4est

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