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Old Feb 28, 2008, 8:51 AM   #1
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I am talking about the internal flash. If I purchase an SB600, can I go over 1/250 ?

I am taking pics of karate, under artifical light, and I need at least 3 times the speed.

Any tip please?

Thanks

Phil
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Old Feb 28, 2008, 10:20 AM   #2
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philgib wrote:
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I am talking about the internal flash. If I purchase an SB600, can I go over 1/250 ?
Yes, the D200 supports FP mode with the SB600. So, you can use shutter speeds faster than the x-sync speed (i.e., it supports High Speed Sync).

Quote:
I am taking pics of karate, under artifical light, and I need at least 3 times the speed.
Probably not. You can freeze action with a relatively slow shutter speed using a flash indoors. Faster Sync speeds are usually more useful outdoors in daylight (where you may want to use a wider aperture setting for DOF purposes in brighter light).

Shutter speed has no bearing on the amount of light from the flash your camera sees (unless you try to use a shutter speed that's faster than the sync speed). That's because the flash burst is very short (usually around 1/1000 to 1/10000 second).

So, as long as you don't have enough ambient light to expose your subject, as in shooting at smaller apertures and lower ISO speeds in darker conditions, the flash itself can freeze the action (again, because the flash burst is very short, and the subject would only be properly exposed during the short flash burst if your camera settings do not allow for ambient light exposure).

For example, in a typical lit interior, you could probably shoot at ISO 100, f/5.6 and 1/200 second and have a very dark (underexposed image). So, using the flash with those camera settings would freeze the action (because the flash burst length is typically going to be 1/1000 second or faster, and that's the only time the subject will be exposed properly).

The problem is that you'll have very limted flash range shooting with the built in flash if you try to stick to settings that would not allow ambient light exposure (i.e., lower ISO speeds, smaller apertures/higher f/stop numbers). So, you may need an external flash to get the desired flash range, depending on your vantage point.

But, with proper camera settings, you probably would not need a faster flash sync speed, unless you wanted to allow a lot of ambient light into the image.

Keep in mind that if you use a sync speed over 1/250 second with your camera with the SB600, flash range will decrease significantly. That's because the flash has to "pulse" the light as the shutter curtains move across the frame (the entire frame will not be exposed at the same time when you go above the sync speed, due to the way a shutter mechanism is designed (giving you a travelling "slit" of light).

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Old Feb 29, 2008, 12:29 AM   #3
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Jim,

As always I have to read your answer several times with the full attention it deserves.
In the mean time, here is an example of howbad it gets. Whites are burned because I metered on the white kimono I guess.

Now that I am looking more cautiously at the attached pic and realise that I did not focused properly and that it may be thecause of the blur despite the flash.





The below one is sharper indeed with the same built-in flash

so it may confirm that it is a focusissue and not a flash issue...


Phil




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Old Feb 29, 2008, 5:52 AM   #4
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Your aperture was wide open at f/1.8, using ISO 400. Depending on how much ambient light was present, you may be getting some exposure from light sources other than the flash. I'd use a smaller aperture (higher f/stop number) and keep ISO speeds set lower. Be careful of flash range, though (it will decrease as you close the aperture and lower ISO speed). An external flash is better.

It does look like you backfocused the first one (but, it also looks like a tad of it could have been motion blur, too).

As the the metering, it's usually a bad idea to use spot metering, unless you're very careful that you are metering on something neutral. If you meter on a darker subject, you'll get overexposed images (chances are, you metered on something dark versus the white uniform for the first one). If you meter on a lighter subject, you'll get underexposed images. Focus distance is sometimes used for flash exposure, too (a backfocused image may have overexposed subjects in the foreground with some camera/lens combos)

I don't know how much weight your Canon would give metering and focus point using manual exposure with flash that way.

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Old Mar 1, 2008, 9:04 AM   #5
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Thank you Jim.

On next session, I will set up my Nikon withiso 200, 5.6 aperture and 1/250 speed using matrix and not spot metering and trying to focus properly. Will come back with results. Distance to subject will always be about 10 feet so will see if built-in flash can cope.

Thanks again

Phil
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Old Mar 1, 2008, 10:33 AM   #6
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You'd be right at the maximum flash range for a properly exposed subject with those settings (f/5.6, ISO 200) from 10 feet away using the built in flash.

To determine flash range at ISO 100, divide the GN (Guide Number) in feet or meters by the aperture setting being used. Then, multiply by 1.4x each time you double the ISO speed.

The GN of your built in flash is 12 meters (approximately 39.3 feet) at ISO 100. That would put your maximum range at around 7 feet at ISO 100 shooting at f/5.6: 39.3/5.6 = 7 feet

At ISO 200, that would get you up to around 10 feet: 7 x 1.4 = 9.8 feet

That would be a full power flash, and recycle times will be longer. So, you may want to set your camera a stop more sensitive (either go ISO 400 and f/5.6, or ISO 200 and f/4) so you're not right on the edge of maximum range, and get a bit better recycle times.

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Old Mar 2, 2008, 11:33 AM   #7
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I found ISO 400 to show too much noise on my Nikon D200 when I use the flash. I will therefore try ISO 200 and F4.

Will revert with results. Some other members may have theirs kids doing judo or karate or whatever so it may be helpful.

Phil
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Old Mar 2, 2008, 11:48 AM   #8
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Phil,

Maybe you should try posting your pics in the Sports & Action Photos Forum.

http://forums.steves-digicams.com/fo...ight=taekwondo

the Hun



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