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12-19-2008, 05:38 AM   #1
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Low light flash assist useless?

I"ve recently been trying wireless flash photography, and works really well.

However, this is the first time I've really had to deal with the on board flash. And I'm confused as to the purpose of the flash focus assist in low light levels.

Let me preface by saying, I usually try to focus on high contrast areas when light is low; however, in this case, I have the camera on a remote, and I'm framing the shots for a preconceived shot, and the option of finding a highlight to focus on before recomposing the shot is not an option.

So imagine it's a group shot with the photographer included in the picture and the ambient lights turned off as to not clash with the white balance of the flash Ja?

Now here's what I don't get.

The camera will buzz out light, stop, and then the camera will try to focus with no light. Then it will buzz out light, stop, and then the camera will try to focus.

I'm stupefied by this behavior. Why wouldn't the camera try to focus when the light it actually *being* emitted from the flash?

As it is now, the flash sends out that buzzing modeling light that it uses for focus assist, stops, and then the auto focus just sits in the dark stupefied as to what it's supposed to focus on before it repeats the process. It eventually finds a lock, but i can take 2 or 3 repeats of this loop.

And I know from experience how much light the K10D needs to acquire focus, and it's *much* less than the focus assist buzz at about 6 feet.

Why on earth does the autofocus wait until after the flash buzz is over before it starts to move the lens? It makes no sense.

Am I doing something wrong?

12-19-2008, 06:33 AM   #2
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First of all, I believe (others may try a different approach) that when you use a camera with remote (on tripod or whatever), you should use manual focus. That is because as you said, you have a "preconceived" framing. Your subject is at known distance and not moving (as to affect focus point).

I pretty much understand the picture you are trying to take. Just use manual focus. Prefocus and preframe. Use auto exposure and wireless flash if you want, but use MANUAL FOCUS.

Under conditions described (dark room), if camera is on autofocus, it will try to focus before picture is taken. If its dark, then the rtf flash will trigger to provide "some light" so the af sensors can lock to something. If you simply manual focus, the camera will not have to do all the buzzing, lighthing, attempt to focus.. thing.
12-19-2008, 07:25 AM   #3
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Good info!:

"I pretty much understand the picture you are trying to take. Just use manual focus. Prefocus and preframe...."
12-19-2008, 12:49 PM   #4
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QuoteOriginally posted by rburgoss Quote
First of all, I believe (others may try a different approach) that when you use a camera with remote (on tripod or whatever), you should use manual focus. That is because as you said, you have a "preconceived" framing. Your subject is at known distance and not moving (as to affect focus point).

I pretty much understand the picture you are trying to take. Just use manual focus. Prefocus and preframe. Use auto exposure and wireless flash if you want, but use MANUAL FOCUS.

Under conditions described (dark room), if camera is on autofocus, it will try to focus before picture is taken. If its dark, then the rtf flash will trigger to provide "some light" so the af sensors can lock to something. If you simply manual focus, the camera will not have to do all the buzzing, lighthing, attempt to focus.. thing.
Yes, thats good advice.

I imagine one of the problems going on, is that if the camera uses the onboard light for focusing, it has to sequence such use, so that the remote flash doesn't use the focus pulse as the signal for flashing.

Another possible way besides manual focusing on a tripod, is to set up the menu such that the AF is disabled for the half shutter, and only occurs for the AF button, if your camera has that option. That way, you can autofocus with the AF button, then go ahead with the shutter whenever you want, without causing the AF to occur again.

Phil

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