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08-24-2009, 10:53 PM   #1
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Blurred pictures with slow-speed sync

When not using flash, my k20d in Av mode automatically adjusts the shutter speed and sensitivity so that I get a properly exposed picture with a shutter speed that is fast enough to reduce the possibility of blur.

But I've noticed that when I'm using flash and slow-speed sync, the sensitivity will increase somewhat to compensate for a slower shutter speed, but not enough. The shutter speed is too slow and the sensitivity won't go above 640, even though I've set it's max to 3200. I don't understand why it behaves differently with slow-speed sync flash compared with no flash.

Can anyone explain?

08-25-2009, 12:46 AM   #2
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I noticed you mentioned Av mode. From what you mentioned, I believe you are also in Auto ISO.
You do not have full control of shutter speed while in Av mode and Auto ISO. If you increase the aperture, and the ambient lighting is fairly bright, the Exposure system will likely reduce the ISO first before it starts to increase the shutter speed. And I'm sure the exposure line behaves differently once you have flash turned on.

I would suggest switch to Tv mode, you can set whatever shutter speed you need, and the exposure system will adjust the appropriate Aperture and ISO. or TAv, where you have full control over Shutter and Aperture..

The camera allows you full control...you just have to know how to use it.
08-25-2009, 07:11 AM   #3
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Another way is to custom the front dial to adjust ISO setting directly. You can change it in the custom settings menu.

I typically shot in AV mode, with auto ISO. But sometimes when the camera decided to use a slow shuttle speed (when using a wide angle lens comes to mind), I'll increase the ISO manually to attend the shuttle I want to freeze action, or reduce the ISO if I'm shooting a static object.
08-25-2009, 07:42 AM   #4
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QuoteOriginally posted by samiam Quote
When not using flash, my k20d in Av mode automatically adjusts the shutter speed and sensitivity so that I get a properly exposed picture with a shutter speed that is fast enough to reduce the possibility of blur.

But I've noticed that when I'm using flash and slow-speed sync, the sensitivity will increase somewhat to compensate for a slower shutter speed, but not enough. The shutter speed is too slow and the sensitivity won't go above 640, even though I've set it's max to 3200. I don't understand why it behaves differently with slow-speed sync flash compared with no flash.

Can anyone explain?
I have found that the slow-speed sync does not provide adequate control over the shutter speed, invariably it is too slow and that causes some image blur. I have adopted the practice of using manual exposure to drag the shutter and avoid that black background when using indoor or low light flash; that allows me to maintain a shutter speed sufficient to avoid image blur.

When using flash as fill, I move to hyper program and with the flash mounted the shutter is limited to the sync speed of 180. I dial down the flash to control the amount of fill required. Well, sometimes I dial up the flash to darken the background to make your subject stand out. Hyper Program is my standard mode when using the camera hand held, you have instant control over both shutter and aperture values.

08-25-2009, 10:14 AM   #5
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You are correct, KittyKat -- I am in AutoISO. I could switch to Tv and adjust the shutter speed as need. My front dial is set for sensitivity adjustment, so I think I could crank that up as well until I get a proper shutter speed...

But I don't understand why the exposure line behaves differently with flash on in slow sync.
08-25-2009, 10:17 AM   #6
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QuoteOriginally posted by mcjm78 Quote
Another way is to custom the front dial to adjust ISO setting directly. You can change it in the custom settings menu.

I typically shot in AV mode, with auto ISO. But sometimes when the camera decided to use a slow shuttle speed (when using a wide angle lens comes to mind), I'll increase the ISO manually to attend the shuttle I want to freeze action, or reduce the ISO if I'm shooting a static object.
Yep, I've got the front dial set that way. And that works. I'm just surprised and confused that the camera doesn't raise the sensitivity enough when flash is on. And yet it does when flash is off.
08-25-2009, 10:19 AM   #7
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QuoteOriginally posted by MikePerham Quote
I have found that the slow-speed sync does not provide adequate control over the shutter speed, invariably it is too slow and that causes some image blur. I have adopted the practice of using manual exposure to drag the shutter and avoid that black background when using indoor or low light flash; that allows me to maintain a shutter speed sufficient to avoid image blur.

When using flash as fill, I move to hyper program and with the flash mounted the shutter is limited to the sync speed of 180. I dial down the flash to control the amount of fill required. Well, sometimes I dial up the flash to darken the background to make your subject stand out. Hyper Program is my standard mode when using the camera hand held, you have instant control over both shutter and aperture values.
Interesting...

What do you mean by "drag the shutter"? Not familiar with that term.
08-25-2009, 10:27 AM   #8
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QuoteOriginally posted by samiam Quote
Interesting...

What do you mean by "drag the shutter"? Not familiar with that term.
It means to intentionally reduce the shutter speed so the flash fires at some point during the exposure, therefore letting in more ambient light before the flash fires and freezes the action of the subject.

08-25-2009, 11:43 AM   #9
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