Tim Gray
Well-known
boy_lah - Love that last picture of the boy and the chess game.
I agree with ferider. I just did the calculations and then read the thread. On full frame, a 28mm has a horizontal field of view of 65 degrees. So from the center to the edge of the frame it's 32 degrees. At .7m, if you shift over 10 degrees, you introduce an error of 1 cm, halfway over to 15 degrees, it's 2.6 cm, 25 degrees -> 7.5 cm, etc. It gets worse as you move over more. Anyway, the point is, at 28mm f/2.8 and .7m, the worse case scenario, you have 10 cm DOF. I know that's not a perfect number since DOF is a fuzzy concept designed for a specific format and print size BUT, doing a little focus and recompose shouldn't hurt you too much. If you move back to 1 m, you double that DOF to 21 cm. Or stop down a stop.
I'm not saying you shouldn't compensate for focus shift. You can do the lateral slide as suggested, or tweak the focus to be a little further when you recomposing by a lot. Or do what Roger suggests right above. I've found that for a lot of instances, focus-recompose doesn't affect things very much at all as long as you are not SUPER close and doing a drastic recompose while shooting wide open. But with a 28mm lens, you should be fine most of the time.
Another thing to think about: if the 1 cm shift is introducing horrendous focusing errors, when taking pictures of people, it's easy for the combined body sway of two people (you and the subject) to add up to > 1 cm.
I agree with ferider. I just did the calculations and then read the thread. On full frame, a 28mm has a horizontal field of view of 65 degrees. So from the center to the edge of the frame it's 32 degrees. At .7m, if you shift over 10 degrees, you introduce an error of 1 cm, halfway over to 15 degrees, it's 2.6 cm, 25 degrees -> 7.5 cm, etc. It gets worse as you move over more. Anyway, the point is, at 28mm f/2.8 and .7m, the worse case scenario, you have 10 cm DOF. I know that's not a perfect number since DOF is a fuzzy concept designed for a specific format and print size BUT, doing a little focus and recompose shouldn't hurt you too much. If you move back to 1 m, you double that DOF to 21 cm. Or stop down a stop.
I'm not saying you shouldn't compensate for focus shift. You can do the lateral slide as suggested, or tweak the focus to be a little further when you recomposing by a lot. Or do what Roger suggests right above. I've found that for a lot of instances, focus-recompose doesn't affect things very much at all as long as you are not SUPER close and doing a drastic recompose while shooting wide open. But with a 28mm lens, you should be fine most of the time.
Another thing to think about: if the 1 cm shift is introducing horrendous focusing errors, when taking pictures of people, it's easy for the combined body sway of two people (you and the subject) to add up to > 1 cm.
Al Kaplan
Veteran
If the picture is interesting enough don't worry about it! There are times when you'll miss optimum focus even with autofocus. The delay of autofocus can mean not capturing the moment. Hell, just the mirror delay in an SLR can do that. A too slow shutter speed can add more blur, but that can mask focussing error, perhaps a good thing.
If you want nice sharp photos of relatively static subjects you need a view camera and a sturdy tripod, and you have to learn how to use it. To me at least Leica photography is something else.
I just posted a series of three pictures on my blog 21 Oct. 2009 http://thepriceofsilver.blogspot.com.
The first two have both focus error and motion blur, the third is reasonably sharp, but when you're five feet away from two chicks that suddenly start screaming at one another, one standing on a bed then jumping off while throwing a punch...you SHOOT! They calmed down, made up, and the third (reasonably sharp) picture shows them walking out of the room together.
If you want nice sharp photos of relatively static subjects you need a view camera and a sturdy tripod, and you have to learn how to use it. To me at least Leica photography is something else.
I just posted a series of three pictures on my blog 21 Oct. 2009 http://thepriceofsilver.blogspot.com.
The first two have both focus error and motion blur, the third is reasonably sharp, but when you're five feet away from two chicks that suddenly start screaming at one another, one standing on a bed then jumping off while throwing a punch...you SHOOT! They calmed down, made up, and the third (reasonably sharp) picture shows them walking out of the room together.
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boy_lah
Discovering RF
More shot at f1.4 - but this time on film
