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01-16-2013, 10:11 AM   #1
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What is Happening With the Flash (During Snowfall Photos)?

Hi folks,

I can't quite figure out what is happening with some flash shots (using the K5 pop-up flash). I've been taking photos during snowfalls and on occasion, roughly 1/3 of the frame will fall in shadow. In other words, 2/3 of the snowflakes will illuminate as expected, but 1/3 of them do not.

Is this simply the shadow of the lens? The attached was shot with a Sigma 17-70 at its widest. Typically I'll get a slight shadow on all flash shots with this lens, but not like this. It only seems to happen with snow. Results are inconsistent, though. These ones came out great:

Flickr: Search bryanscott's photostream

But you can clearly see the shadow in the attached. I believe I mistakenly had the flash set to Trailing Curtain Sync for this shot. Could that be the culprit?

Any help is greatly appreciated.

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01-16-2013, 10:18 AM   #2
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Do you have any more examples where there is a shadow like this? My best guess so far: due to the fact that the shadow is diagonal across the frame, I don't believe its a lens shadow or shutter curtain issue, but a hand shadow. I think your hand may be accidentally blocking the flash a bit.
01-16-2013, 10:20 AM   #3
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Will post more photos later today. You could be right about that, although it's never been an issue for me before.
01-16-2013, 10:21 AM   #4
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QuoteOriginally posted by enoeske Quote
Do you have any more examples where there is a shadow like this? My best guess so far: due to the fact that the shadow is diagonal across the frame, I don't believe its a lens shadow or shutter curtain issue, but a hand shadow. I think your hand may be accidentally blocking the flash a bit.
Lens, hand or both. the 17-70mm is not a small lens, the manual will tell you that even with the kit lens you'd get a shadow with the hood and the 17-70mm is a fair amount bigger. That said, it very well could be a forearm in the way as well depending on how you hold your camera.

01-16-2013, 10:24 AM   #5
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These were blizzard conditions (whereas the shots on Flickr were not), so it's quite possible my normal shooting posture was compromised. Will post a couple more photos later today.... Thanks for your quick replies guys.
01-16-2013, 08:25 PM   #6
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Here are two more examples where roughly 1/3 of the shot is in shadow. Could it really be that my hand got in the way??
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01-18-2013, 01:11 PM   #7
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QuoteOriginally posted by slowdive101 Quote
Here are two more examples where roughly 1/3 of the shot is in shadow. Could it really be that my hand got in the way??
nothing related to your post - checked out your site, it has been quite awhile since i've been to the peg! Loving the storm/city photos you've got up. I lived in MB for a few years, went to school at providence college (outside of the city, if you've heard of it). Lived in Winnipeg for a year, as well as out in steinbach and worked at friesens (the book publisher) in altona for a couple of summers too.

OK back on topic. The new photos make me think it is something to do with the lens, as you can see the shadow is curved. I'm guessing though that not all of your photos exhibit this, which puts us back at square one. It might be a shutter sync problem, what are the shutter speeds being used? They must be pretty slow, so I don't think it would be that (and usually that would result in the actual shutter covering part of an image). Oh, were these newly taken or from the same night as the first photo? Ultimately I think you'll have to do some experimenting on your own to figure out what is going on, what camera settings or physical properties are causing this to occur.
01-18-2013, 02:26 PM   #8
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It seems that it has to do with the lights. Maybe the sensor is picking up the reflection from the lights not the flash, or proportionately more accentuating them.

01-18-2013, 02:42 PM   #9
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QuoteOriginally posted by derekkite Quote
It seems that it has to do with the lights. Maybe the sensor is picking up the reflection from the lights not the flash, or proportionately more accentuating them.
That could be part of it too. The flash should also be smart enough to shut itself off once it determines it has output enough light - I wonder if having the bright snow spots is causing the flash to pre-maturely turn off causing a strobe across only the partial frame.
01-19-2013, 12:03 AM   #10
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