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10-30-2015, 06:31 PM   #1
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Dark strip moves across frames

I think my shutter somehow got out of time. In any series of shots, there is a dark brown stripe that moves from the top of the sensor to the bottom and back. I can't post pics right now, but this but really messed up the last opportunity to take pics of my sister's band performing at a football game before she graduates. The problem gets progressively worse with faster shutter speeds. Iso and aperture seem to have no affect on the issue. Anything under 1/100 isn't really noticeable, but at 1/200 and above, it's really had. Pics shot at 1/320 result in half the frame being nearly 2 ev underexposed (by eyeballing it, anyway). The problem has nothing to do with lens or aperture control, because it evens happens when you take the lens off and shoot with just the body cap in place.

Has anyone else encountered this issue? Is there any way to fix it other than sending it back to pentax for repairs?

Thanks,
Will


Last edited by willskywalker93; 10-30-2015 at 06:38 PM.
10-30-2015, 06:42 PM   #2
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did you use a manual flash??
10-30-2015, 06:45 PM   #3
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no flash. Just stadium lighting. It looks a lot like flash sync issues, just without the flash.
10-30-2015, 07:02 PM   #4
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If the same thing happens when you're shooting the sky during the day, then there's something wrong with the shutter (are you using a K-30/K-50?). Otherwise, the stadium lighting could be to blame. Strange underexposure like what you're describing can happen indoors with typical lightbulbs, for instance.


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10-30-2015, 07:11 PM   #5
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sorry, I'm on k3. I happens with stadium lighting and indoor fluorescents. I'll try the sky when it's light outside tomorrow. It's a consistent cycle from side to side of the frame, every third frame seems to be decent the stripe is on top and bottom of sensor not so bad in the middle.

I've shot in this same stadium with this same setup many times, never an issue.

Thanks for the replies, guys!
10-30-2015, 07:22 PM   #6
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Based on your description, I don't think this is a shutter issue.

Can you post examples?


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10-30-2015, 07:35 PM   #7
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Yeah, give me a bit. Not near a pc.

It's wasn't a systematic zone white balance either, I switched to manual wb and it did the same thing. Does it on continuous and single frame drive modes.
10-30-2015, 08:09 PM   #8
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The first set of shots was taken from the press box at my sister's school while shooting towards the field. I think these were like 1/320 and f3.2 in TAv mode (probably ISO 6400, ettr by 1/3 or 2/3 ev) at around 200mm on my sigma 70-200 hsm ii. The next series was the same settings pointed at a white wall inside the press box. I took one more series with the lens off, they looked just like the ones with the lens on and pointed at the wall., just slightly different color.

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10-30-2015, 08:10 PM   #9
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QuoteOriginally posted by willskywalker93 Quote
I've shot in this same stadium with this same setup many times, never an issue.
Do you have old pictures at these shutter speeds as a comparison?

edit- seeing your examples it looks like it's the cycle of the fluorescent lights. Slow shutter speeds catch an entire cycle (or multiple cycles) so things average out, but at high speeds you'll only nick a part of it. The colour temperature and output change over the cycle, so you expose different parts of your sensor to different parts of the 'wave'. You may also get lucky and hit a part of the wave that's fairly consistent over your exposure.

Last edited by BrianR; 10-30-2015 at 08:16 PM.
10-30-2015, 08:17 PM   #10
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Here they are. I just realized the ones of her are at 1/500, but the ones of the wall are at 1/320. The following set was also at a stadium with the same lens at 1/320 shot the first weekend in September. No issues with these.
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10-30-2015, 08:24 PM   #11
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Yet the bands are there at 1/320s when shooting at the sky.. so I'm not so convinced it is the lighting of the stadium.
10-30-2015, 08:48 PM   #12
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that wasn't the sky. It was a wall in a room either fluorescent bulbs.

And I'll be a son of a monkey's uncle. You nailed it, BrianR and Adam. I've never had that issue in that stadium before, but I just shot 1/500 under incandescents and it's totally fine. Shot again in another room of my house under fluorescents and the band is there. I guess it's possible that the other times I'd shot there I just got incredibly lucky, or the different sets of lights were all somewhat out of phase and lit evenly. I knew those light sources were all based on waves, but I guess I had never encountered this issue with them all being in phase.

Thanks again guys! I can stop being mad at my k3 now. I'll shoot daylight tomorrow to make sure, though.

Will

Well, thanks guys!
10-30-2015, 08:56 PM   #13
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Looks like you are capturing the flicker of florescent and HID stadium lights. They basically cycle 60 times a second (50 in Europe) . Any light source that has a ballast will do that. The human eye puts it together so you don't notice it. You will see it in TV slo-mo replays if the camera is pointed at the lights. The newer Canon high end cameras automatically detect and eliminate this.
10-30-2015, 09:15 PM   #14
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QuoteOriginally posted by eddaytona Quote
Looks like you are capturing the flicker of florescent and HID stadium lights. They basically cycle 60 times a second (50 in Europe) . Any light source that has a ballast will do that. The human eye puts it together so you don't notice it. You will see it in TV slo-mo replays if the camera is pointed at the lights. The newer Canon high end cameras automatically detect and eliminate this.
That's exactly what it is. The camera model and make is irrelevant. If newer Canons detects and eliminates, that's a very neat in camera post processing trick.

Happens to me a lot in dance studios with HID. Shutter speed up at 1/320 to stop motion. Depending where I happen to hit the 60Hz cycle, Red to Blue shift. Less noticeable if I have a lot of ambient ( bright sunny day). You can knock down the Blue & Purple saturation in ACR but normally, I simply convert to B&W. When I have a studio session and can add mono lights, they don't matter .

Slow your shutter speed to 1/125 and you'll see it lessen. At 60HZ, everything is fine. But if that is the light you are recording and you're shutter is a fraction of 60HZ, you'll see it..
10-30-2015, 09:23 PM   #15
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Yeah, makes perfect sense, I understand the electrical principles of it all, I am just shocked that I've never encountered this issue before, or at least noticed it.
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