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Old Apr 26, 2005, 10:21 AM   #1
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What does the term slow AF in low light mean...i have heard that the Konica A200 has this disadvantage, so does it take very bad shots in the night ?

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Old Apr 26, 2005, 11:12 AM   #2
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Most auto-focus systems do not perform well in low light. Some cameras have a focus assist light that comes on to assist in focusing but I am not convinced that it works very well. I generally find that manual focus is best for low light situations.

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Old Apr 26, 2005, 9:47 PM   #3
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I have to agree with calr on this. MOST cameras do not focus well in low light, and the assist beam is very poor on most cameras. Digital SLR's have a stronger point here. I've taken a lot of pictures at school dances with it, and it does work very well with the assist beam. There are rare occasions though, you will be in very low light, that not even the assist beam will work. Just like calr said, manual focusing is great in this situation.

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Old Apr 27, 2005, 4:17 AM   #4
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are the Konica A200 or the Canon powershot A95 or G6 good at taking pictures in the night ?

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Old Aug 13, 2007, 6:50 PM   #5
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Assuming calr and tswen are right (not that I'm doubting them) is it safe to assume that not having AF Assist built into the DSLR (Canon's)shouldnot bea factor in choosing a DSLR?

I mean how vital is AF Assist in "everyday" shooting? Whether you're in a low-light situation (e.g. dimly lit bar) or a well lit occasion (e.g. sunny beach). Assuming you do want to rely on the camera's and the lens' ability to AF and not focus manually.

In a well lit scene would you not need to count on the help of the AF Assist? Also, is the AF Assist always active in every shot (lets say we're talking about a DSLR where they have an external AF Assist lamp built-in)...or, if we're talking about a Canon DSLR with an external flash).

Thanks.

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Old Aug 13, 2007, 8:41 PM   #6
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AF assist is only necessary in low light situations, such as the dimly lit bar you mention. Some cameras use the flash for AF assist (mostly SLRs), and others have a separate AF assist light. If you are attempting to take candid photos, either will announce that you are shooting a picture.

style="BACKGROUND-COLOR: #000000"If the light is too dim for autofocus, it is probably also too dim to get good pictures without flash. (the reason some cameras use the flash for AF assist), unless you use very high ISO and large aperture lenses.

style="BACKGROUND-COLOR: #000000"If your subject is still, you should not have to worry about slow AF. If it is moving, and the light is too low for good AF, you will probably end up with blurry pictures anyway, unless you are using flash. If so, you should pre-focus manually.

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Old Aug 13, 2007, 11:29 PM   #7
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VTphotog wrote:
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AF assist is only necessary in low light situations, such as the dimly lit bar you mention. Some cameras use the flash for AF assist (mostly SLRs), and others have a separate AF assist light. If you are attempting to take candid photos, either will announce that you are shooting a picture.

style="BACKGROUND-COLOR: #000000"If the light is too dim for autofocus, it is probably also too dim to get good pictures without flash. (the reason some cameras use the flash for AF assist), unless you use very high ISO and large aperture lenses.

style="BACKGROUND-COLOR: #000000"If your subject is still, you should not have to worry about slow AF. If it is moving, and the light is too low for good AF, you will probably end up with blurry pictures anyway, unless you are using flash. If so, you should pre-focus manually.

style="BACKGROUND-COLOR: #000000"brian
Ok. So if we're talking about DSLRs like the Canon 30D, then you would have to remember to raise the flash (when shooting in certain low-light situations) or be willing to walk around with an external flash on your camera.But, what if we're talking about cameras where the AF Assist is not part of the built-in flash? Like the Nikons. What then?

I mean, in the case of the Nikons, wouldn't the AF Assist be always on? Whether you're shooting some architecture in the bright Egyptian sun or in a Morrocan bar? Being that the lamp is on the front of the camera. And if so I suppose there wouldn't be any bad points about having the AF Assist working shot per shot. Correct?

Any how, I guess my two choices will still be between the replacements for the Canon 30D and the Nikon D200. And yes I alrady have a camera to shoot with (there's always some guy who says "...there's always a new camera....buy now...etc."...heh).

Hope to see them both this year. Not that I'm in any hurry.
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Old Aug 15, 2007, 9:43 AM   #8
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Both of the models you're looking at (Canon EOS-30D and Nikon D200) have custom settings in their menus for AF assist (without an external flash attached, Canon uses the built in flash, Nikon uses a lamp). You can leave it on or off as desired.

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Old Aug 15, 2007, 11:58 AM   #9
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JimC wrote:
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Both of the models you're looking at (Canon EOS-30D and Nikon D200) have custom settings in their menus for AF assist (without an external flash attached, Canon uses the built in flash, Nikon uses a lamp). You can leave it on or off as desired.
Thanks JimC. I was aware of that. And that in the case of the 30D the flash will strobe when "AF Assisting". Which would be pretty annoying in portrait situaitons. So, if I do go with the 30D's replacement I'd probably rely more on an external flash or end up manual focusing in low light.

Have a good day.
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Old Aug 15, 2007, 1:36 PM   #10
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Both the Nikon and Canon you're looking at should be pretty good in most low light conditions you're want to use one in, provided the lens is up to the task.

Lens quality impacts Autofocus. If you have a brighter lens with larger available apertures (smaller f/stop numbers), the camera's Autofocus sensors get more light.

You can buy a 50mm f/1.8 AF lens for $100 or less for either of those cameras that's going to be roughly 10 times as bright as a typical kit lens at 50mm (since they're down to a widest available aperture of around f/5.6 by the time you zoom in much with one). f/1.8 is 10 times as bright as f/5.6.

How a lens is geared also impacts focus speed. For example, Macro lenses are usually geared towards finer focus adjustments (more movement of the focus ring to change focus distance, with a greater range of close to far). So, most tend to focus slower. Some have focus limiters built in to help out with the range part.

In the case of a body driven lens (as are many lenses designed for Nikon), the camera's focus motor also comes into the equation. For example, a pro level body is going to have a faster motor with more torque compared to an entry level model.

Some lenses have focus motors built into them (all Canon lenses do, and a number of Nikkor lenses do), and the type of focus motor in the lens comes into the equation with Canon lenses (you've got several kinds, including two different types of USM).

The sophistication of the Autofocus Algorithms is another factor, as is the quality and sensitivity of the AF sensor assembly and the speed of the hardware based processors in the camera.

If you mean typical low light condition in interiors with lights on, a brighter prime can usually focus OK with the bodies you're looking at (and a good quality zoom can often get by without any AF assist).

If you're outside in very dark conditions trying to do a long exposure night shot, use manual focus if you can't find something bright in the scene to focus on (you're not going to be close enough for most of those types of shots to use AF assist anyway).

I leave AF assist turned off, since I find it annoying and think it spoils the candid nature of many photos, even when you're close enough to use it.


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