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eric s Apr 29, 2004 9:04 PM

Improving focus speed?
I missed a picture today because my 10D hunted slightly in the wrong direction and then changed direction and found the focus.

But the moment was lost, and the bird soon flew away without doing the same squawk and wing ruffle.

So this got me wondering about ways to improve focus speed.

Does the 10D do anything other than contrast detection? Doesn't that mean it just has to guess which direction to change the focus and see if it gets better... and if not, change direction and off it goes.

Why don't they use distance to speed up the initial focus? Since Nikon uses distance info in their flash, and Canon added this in ETTL-2, that means they have the info. Why couldn't they use the distance to know exactly what direction to start focusing in, and even to give them an rough idea of where to focus to.

Would this work? It just seems too simple, so maybe they already do it.


mrkryz Apr 29, 2004 9:47 PM

Which lense were you using and which shooting mode?

eric s Apr 29, 2004 10:33 PM

100-400L in continuous drive mode, one shot.

I'm not complaining about the lens or camera (well, I'd like it to do better, but I don't think I can... to get a better AF system, I have to buy a 1D, 1Ds, or 1D-mark 2 and it isn't worth that much to me. And to get a better AF lens at similar focal length & image quality I need the 400 f5.6, which is cheaper, or some really expensive 400,500,600 primes.)

I was just thinking creatively. Why not use distance info to help speed up AF? Or do they already do this?


mrkryz Apr 29, 2004 11:03 PM

Dont quote me but I have from what I understand it does not use distance info. What I do know however is that the AF sensor in the 10D is a "consumer" sensor not a "professional" sensor. This is from Canon press material I read somewhere a while back. They state that the "professional" body cameras utilize focus sensors that are 3 times more accurate and faster. Aside from that I guess a lot is to be taken into consideration ... especially if your using a long lense with a large aperature ability the DOF to scan can make it tedious for the camera to figure out, especially if there is low light/lack of contrast/detail etc...

But what you say makes perfect sense.... It should implement the distance information to reduce the hunting in some situations. Canon favors front focusing slightly so if that were taken into consideration and the camera progressively scanned focus faway from the given distance for the current focus point it might help a bit when using long glass in actions photos.

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