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:

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 Stobblehouse 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.

Anna said...

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. :-)

Eolake Stobblehouse said...

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

Anna said...

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

Anyway, I'll see.

Eolake Stobblehouse said...

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

Anna said...

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. :-)

Eolake Stobblehouse said...

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.

Anna said...

Yes.

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

:-)