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12-18-2009, 10:07 AM   #1
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horizontal bars in video

I have found this (bug?) to occur only in live view when the lighting conditions are just so. If I snap a picture, the bars are not present, but if they are recorded in video they show up. Below is a link to a short mp4 sample video. I am wondering if this is due to some setting being off or if I need to exchange my camera.

http://www.nickquest.com/banding.MP4

12-18-2009, 10:43 AM   #2
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You are using k-x or k-7?
I have a similar problem, but in vertical thin rows:

https://www.pentaxforums.com/forums/pentax-video-forum/83774-k-7-strange-vert...ows-movie.html
12-18-2009, 10:48 AM   #3
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I have a k-x. Also I'm using a Pentax 50mm 1.4 manual lens. I haven't tried to repeat the result with the stock lens yet. Are you using the stock lens?
12-18-2009, 11:04 AM   #4
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QuoteOriginally posted by jeans Quote
I have a k-x. Also I'm using a Pentax 50mm 1.4 manual lens. I haven't tried to repeat the result with the stock lens yet. Are you using the stock lens?
I'm pretty shure that these problems are not from the lens.
I also use a k-50mm 1.4 and a A28mm 2.8 almost the time.
I also use a sigma 17-70 2.8-4.5, and get the nasty vertical thin lines in low light, with every lens.

12-18-2009, 12:23 PM   #5
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Yeah, I suppose not. I just thought maybe the camera was doing something weird because of a setting that is due to the manual lens. Next I'm going to try and repeat the bars with the stock lens and then I guess return the camera to Amazon. I've only had it a week.
12-18-2009, 01:37 PM   #6
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Has anyone else had this problem with the K-X?
12-18-2009, 09:13 PM   #7
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QuoteOriginally posted by jeans Quote
I have found this (bug?) to occur only in live view when the lighting conditions are just so. If I snap a picture, the bars are not present, but if they are recorded in video they show up. Below is a link to a short mp4 sample video. I am wondering if this is due to some setting being off or if I need to exchange my camera.

http://www.nickquest.com/banding.MP4
I've seen similar lines in some of my movies with fluoro lighting.
Although nowhere near as severe as your example.

K-7 btw

mutters

Last edited by Mutters; 12-18-2009 at 09:23 PM.
12-18-2009, 09:58 PM   #8
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QuoteOriginally posted by Mutters Quote
I've seen similar lines in some of my movies with fluoro lighting.
Although nowhere near as severe as your example.

mutters
Thanks. After you suggested this I decided to test it on non florescent lighting. Such lighting was surprisingly hard to find since all the bulbs at my house are the energy saver variety. I guess my lcd monitor must have a florescent backlight because it had very bad bars. Anyway I determined that it only happens on high shutter speeds and only on florescent light! This is good and bad news, it means I understand the problem somewhat, but I'm pretty certain It wasn't like this when I first got the camera. At least I think it wasn't. Oh I also determined that it does show up in photos as well, only not nearly as bad as in video. Also only one bar appears in photos that is much thicker and more blurred. It reminds me of scan lines, like they're actually moving very fast. Do you think this is an artifact related to CMOS rolling shutter?

12-19-2009, 09:28 PM   #9
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QuoteOriginally posted by jeans Quote
Thanks. After you suggested this I decided to test it on non florescent lighting. Such lighting was surprisingly hard to find since all the bulbs at my house are the energy saver variety. I guess my lcd monitor must have a florescent backlight because it had very bad bars. Anyway I determined that it only happens on high shutter speeds and only on florescent light! This is good and bad news, it means I understand the problem somewhat, but I'm pretty certain It wasn't like this when I first got the camera. At least I think it wasn't. Oh I also determined that it does show up in photos as well, only not nearly as bad as in video. Also only one bar appears in photos that is much thicker and more blurred. It reminds me of scan lines, like they're actually moving very fast. Do you think this is an artifact related to CMOS rolling shutter?
Hi jeans
Most monitors have fluoro backlighting, which is now being replaced with Led backlighting.
Depending on where you are, your AC electrical current cycles at 50 or 60 Herz.
So any shutter speed slower than 1/50th or 1/60th sec will give you a band free image.
Anything above it will show banding. The number per image is directly related to the shutter speed and electric supply's frequency.
I imagine rolling shutter would also add to the problem.

mutters
12-20-2009, 01:04 AM   #10
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I get a fixed purple line visible in video mode under certain lighting conditions on the left hand side of the frame, im sure its a sensor defect but I have never seen it on any photos just video.
12-20-2009, 01:23 PM   #11
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If you are getting colour shifts under florescent lights, it is not the cameras fault.

Florescent lights flicker through a spectrum of colours at a high speed to simulate a specific colour temp. That is how some bulbs are warm, some are cool.

If your shutter speed is close or faster then the flicker speed of the florescent bulb, you will see the different bands of colour. You can test this by taking a series of shots of a white object under florescent light, while gradually increasing the shutter speed. At one point you will start to see colour bands.
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