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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old December 22nd, 2009, 06:41 PM   #1
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3 yellow horizontal lines

I just tried to film with the 7D and i saw 3 yellow horizontal lines on the screen.
I have never seen it before.
what is it?
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Old December 22nd, 2009, 08:32 PM   #2
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Are you shooting under fluorescent light? Play with the shutter speed and you'll see the lines move. Hopefully it's not a camera defect =)
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Old December 22nd, 2009, 10:14 PM   #3
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yes, it was under fluorescent light.
As the shooter speed got greater the lines got more noticeable.
The thing is that I have shot at the same place (my studio) many times and never got this before.
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Old December 23rd, 2009, 01:11 PM   #4
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You were probably using a CCD camera before. The 7D is a CMOS camera, and that scrolling bands of lines issue is a CMOS issue.

When shooting under fluorescent, glue your shutter speed to 1/60th (1/50th in PAL territories). That should eliminate the lines. Never use 1/50 or 1/45 under magnetic fluorescents when shooting in an NTSC territory, and never ever ever use faster than 1/120 when shooting under magnetic fluos (or HMIs).
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Old December 24th, 2009, 04:59 PM   #5
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That's strange, I shoot at 24fps 1/50 shutter all the time and in fact shot that way under fluorescents only 2 days ago with no problems. I shoot in offices all the time. There was a time many years ago when shooting 16mm film that we would often get some flickering from certain types of fluorescents, but I haven't seen anything like that in over 20 years.
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Old December 24th, 2009, 06:55 PM   #6
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The closer to 1/60th, the subtler the effect, but it's there. Try modifying your footage in post by exaggerating the contrast and you'll see it clearly (unless, of course, you were shooting under flicker-free electronic ballasts, in which case there won't be a problem). Art Adams wrote an article on PVC (something like "Red vs. the Home Depot Lights") and shows the effect at 1/48th.

Under magnetic fluos or magnetic HMIs or sodium-vapor or mercury vapor lights, the shutter speed is a critical element to get right with CMOS cameras. You can know whether you're going to have a problem or not by cranking up the shutter speed to 1/250; if the horizontal hum bars show up, then you'll have a problem at 1/48 or 1/50 too, just subtler. If the hum bars don't show up even at 1/250, then there won't be a problem at 1/48 or 1/50.

But if you just shoot 1/60 you won't have the problem at all.
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Old December 25th, 2009, 12:08 AM   #7
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I talked to Canon rep and his explanation to why i did not have this problem before was that one of my fluorescent light bulb in my studio is going bed and it is not visible to my eyes but it does to the camera.
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