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Old Feb 28, 2003, 12:15 PM   #1
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Default What is an AF illuminator?

Hey guys,

I was wondering what an AF illuminator is and how important is it to have on a Digicam.

Thanks,

Shiggy
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Old Feb 28, 2003, 1:14 PM   #2
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If you are shooting in low-light situation and the lighting is dark enough that the camera could not achieve a focus lock on its own, then having an AF (autofocus) illuminator would be rather helpful. Basically it shines on the subject when activated, allowing the camera to achieve a focus lock.

Not too many digicams have this feature--I know in the Olympus line the C-5050 does, and I believe Sony F717 does, too. It's a feature found mostly in high-end digicams.

Hope this helps.
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Old Feb 28, 2003, 2:08 PM   #3
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Actually ... every Sony and Canon digicam has an AF-assist lamp of some sort or another. Nikon and Fuji are lagging behind the pack by not having this much needed feature. The new Nikon Coolpix SQ is the first Coolpix to have one, not even the $1200 Coolpix 5700 has AF-assist.

If it's dark enough for flash you need an AF-assist lamp and this is what I have been trying to beat into the heads of the camera makers. It isn't expensive and it -is- a necessary thing to have.

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Old Feb 28, 2003, 2:22 PM   #4
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Thanks guys,

I was wondering because I was deciding between a Nikon 3100 and a Sony P72. The Nikon does not have The AF illuminator and the Sony does so I guess I will get the Sony

Thanks,

Shiggy
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Old Feb 28, 2003, 3:17 PM   #5
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Quote:
Originally Posted by steve
Actually ... every Sony and Canon digicam has an AF-assist lamp of some sort or another.
Oops! Thanks for the info, Steve. I stand corrected!
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Old Feb 28, 2003, 3:51 PM   #6
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Here's how autofocus works, and why it's nice to have an assist beam:

http://www.howstuffworks.com/autofocus3.htm

Just realize that the assist beam is only as good as the distance the internal flash can go (probably less).
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Old Feb 28, 2003, 6:04 PM   #7
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I've been puzzled for a while now as to how my Fuji 602 can take sharp focused flash pics in total darkness.

My question on another forum was 'does the cam default to a focus point within its DOF, since it knows the approximate flash range' or 'does the cam acquire focus during the flash cycle'. I think it impossible for the focus motor to do this and I've never heard it wirring.

I'm still out on an explanation. Ideas so far are: focus is achieved during the flash cycle, but reduced edge contrast confuses the distance measure with ambient or low light, focus distance is preset to the approx flash range, focus in dark is done by infra red for hot human subjects!

Any ideas??
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Old Mar 14, 2003, 6:48 PM   #8
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Does a Oly C4000Z have AF assist? :lol:
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Old Mar 14, 2003, 7:27 PM   #9
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Vox-
I could swear that I read somewhere that under auto-flash conditions the Sony U20 performed its auto focus during the exposure setting pre-flash (first of two flash firings). If this is true, perhaps it's because Sony could pull it off owing to the really small distances and low mass in the U20's optical train allowing fast enough lens movement to achieve acceptable focus. BTW really low light focus accuracy of the U20 isn't all that stellar.
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Old May 4, 2003, 10:10 AM   #10
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Ambientscape,

I don't think the C-4000Z has the AF Illuminator. The FL-40 External Flash DOES have it, however.

I have a theory about this . . . :idea:

I think the design rational is that the AF Illuminator is not needed on the camera because the flash is basically designed to 'assist' ambient lighting - not provide it totally like the FL-40 is capable of. In other words, the assumption is that there is enough ambient light to let the camera get enough of an image to go thru it's contrast detection routine (which is how it focuses - by looking for the point of maximum contrast when the shutter is pressed halfway).
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