Monday, February 01, 2010

Focusing Follies

Focusing Follies, article by Ctein. Like usual from Ctein, a well written technical article, this time about the seldom-talked-about weaknesses of all traditional camera focusing methods, and what might be done about it.

Anna said...
What's that whole story about making focus in tune? I didn't really get it. Just notice that many of my pictures are out of focus with that automatic focus system. Is there a way to improve that?

Eolake said...
Funny enough I've never myself noticed all those accuracies that Ctein talks about.
That's why I noticed and published one more John image, I was checking focus in them, they were taken with a super-critical fast lens. All sharp.

I recommend that you only use the middle focus point, point that where you want to focus, and then re-compose the picture. This is more accurate than letting the camera select the focus point.

9 comments:

  1. What's that whole story about making focus in tune? I didn't really get it. Just notice that many of my pictures are out of focus with that automatic focus system. Is there a way to improve that?

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  2. Funny enough I've never myself noticed all those accuracies that Ctein talks about.
    That's why I noticed and published one more John image, I was checking focus in them, they were taken with a super-critical fast lens. All sharp.

    I recommend that you only use the middle focus point, point that where you want to focus, and then re-compose the picture. This is more accurate than letting the camera select the focus point.

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  3. That's what I do normally, but it does not work all the time. I was thinking I am the stupid one, and well, that may still be, but this article confirms my growing suspicion that there is some problem with autofocus.

    I remember the old times when the camera had those two half-circles in the middle, and if they formed one single circles the image was sharp. And it was.

    Now, with autofocus, I do have problems. Of course sometimes it makes things easier, quicker, but sometimes it is difficult to focus on the object because the camera does not find it (ex: a swan in the middle of a lake). And then it is a real fight with the camera. And if I try manual, as the half-circles are not there, I am not sure about the result. The camera produces that red light when it thinks the focus is ok, but it is not correct, and anyway, as there is a time for reaction between the moment when you perceive the red light and the moment you stop turning the lens, it is again out of focus anyway.

    I spent at least two hours with the swans, and a lot are blurred.

    Anyway, I am convinced it will be different with my new camera. :-)

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  4. I certainly hope so. A white swan neck against a dark lake should be super-easy for the camera to focus on.

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  5. Yeah. But its moving ! Focusing needs some time...

    Anyway, I'll see.

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  6. If you're doing it right, this should be plenty fast enough, unless the swan is starting to fly.

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  7. Haha ! :-)

    Ok, then probably there is a problem with my camera. I was thinking it is only my way of using it...

    Anyway, I'll see. :-)

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  8. If you use only the center focusing point, and point it right, any decent DSLR camera should focus correctly in half a second or such, under most conditions.

    Some of them have trouble in the same circumstances humans would: in low light or low-contrast subjects.

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  9. Yes.

    I hope that with higher low-light sensitivity, the focus will also be more sensitive, and not start pumping so easily.

    :-)

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