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Old Dec 5, 2012, 3:57 PM   #1
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Default quick easy question (i hope)

this is probably a simple question but the answer escapes me.... when i'm shooting basketball on continuous advance, the second picture is darker. This has never happened before last night. i don't think i've changed any settings... ??
thanks. yall have always been a great help.
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Old Dec 5, 2012, 4:11 PM   #2
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Can you post a sample?

Also, what camera and lens were you using?
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Old Dec 5, 2012, 5:11 PM   #3
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sony a700. i usually use 50 1.7 & 85 1.4 and have never had that problem. last couple of times i've also used the tamron 70-200 2.8. that's the one that had the biggest problem, but when i switched to the 85 the second pic was a little darker tho not as much.
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Old Dec 5, 2012, 5:47 PM   #4
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Without seeing the photos you mentioned, I can only guess, but there are some things it could be.

dSLRs only set exposures on the 1/3 f-stop, so it's possible that the first shot might, for instance, be ISO 800, f/2.8, and 1/250, while the second shot could be ISO 800, f/2.8, and 1/320. As a result, the second shot might appear a little darker than the first, though they're both either side of a proper exposure.

It's also possible that the lighting system could be causing variations in the luminance during that fraction of a second that the exposure occurs. Alternating Current cycles 60 times per second (60Hz) which means that some light sources flash, or flicker every 1/120 second, or half-cycle. That's faster than you can tell, but if the light source has a low persistance, it may affect the exposure faster than the camera can account for it. Basically, depending on the light system in use, you may occasionally be taking pictures midway between flickers.

Again, without the actual images, I'm just guessing.
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Old Dec 5, 2012, 5:56 PM   #5
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i shoot (with the 70-200 2.8) 320 2.8 iso 1600 on manual setting so that doesn't vary... i don't have time to figure out how to downsize and post pics. getting ready to head back to the gym. now this is a different gym. all of the other pics have been at our gym so possibly the other theory? but it would be odd that the first pic would be lit well and the second one not so much. i could show you shot info (exif) but that prob wouldn't be helpful. maybe tomorrow i can post some pics.
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Old Dec 5, 2012, 6:31 PM   #6
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correction iso 2000. not that it matters.
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Old Dec 5, 2012, 6:53 PM   #7
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If it happens as a result of the flickering, then a seqence of shots would show minor differences in brightness, so take more than just two. Also, if one circuit is bad, then it might happen more, or more severely in one location than in others. And in a different gym, you might not see it at all.
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Old Dec 6, 2012, 1:14 PM   #8
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tcav i don't know if you can tell anything. i uploaded pics to an album. two sets. they are awful. they are from last night. i tried to upload a couple from our gym but couldn't get them to upload. now these are from raw just saved as jpeg, didn't remove noise or anything so keep that in mind...
any thoughts. . .
last night seemed worse if possible.
headed back in an hour. my internet was down until about an hour ago so couldn't get on here. geez.
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Old Dec 6, 2012, 3:13 PM   #9
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The first four show significant variations in luminance from left to right with the camera held vertically. When you hold the camera horizontally, does the luminance still vary from left to right?

Does it happen elsewhere, or only in gyms? Incandescent lights? Fluorescent lights? Sodium vapor lamps?
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