PDA

View Full Version : yellow horizontal bars showing up



thebullfrog
02-12-2010, 04:37 PM
hey guys,

so i just recently got the 7D earlier this week and so far it's been awesome, passing all of my expectations.

I've just come across 1 problem with it and that is, i'm seeing yellow horizontal bars showing up in my footage...surprisingly not in my images.

i played around with the settings and temp fixed it by adjusting the ISO to high to essentially block it out...it worked but i don't know if it might show up during other times or shooting situations....or if it might just be at the gym.

the bars only started showing up when i was in my gym yesterday, they don't have fantastic lighting in there...and i did do white balance...so i dont know if that may be the problem.

the following still is a frame grab from one the test clips i did.

http://img205.imageshack.us/img205/9250/yellowbars.png

settings for that video clip was
iso 1250, custom WB, standard picture style...

any help would be greatly appreciated.

Barry_Green
02-12-2010, 05:12 PM
Set your shutter speed on 1/60th and never ever ever ever change it.

thebullfrog
02-12-2010, 06:32 PM
Thanks barry, i'll try it out tomorrow when i go back to the gym....

Barry_Green
02-12-2010, 09:17 PM
Please, everyone, learn from this. Fluorescent, HMI, mercury vapor, sodium vapor -- they all interact with CMOS sensors to create these bands, and the only way to get rid of it is to set your shutter speed to match the power frequency of where you live.

Spread the word, so people see this BEFORE they run into a situation where they have ruined footage.

If you're using a CMOS camera, in the US or other NTSC territory, set your shutter speed at 1/60th and just leave it there. Don't go for 1/50th, don't go to 1/48th, leave it at 1/60th.

If you're in a PAL territory, use 1/50th, and only 1/50th.

shaocaholica
02-12-2010, 09:30 PM
Are these artifacts visible on the LCD? Just in case I forget since I might have had the camera set to 1/50 when shooting outdoors.

dcloud
02-13-2010, 01:32 AM
oh. so is that why i couldnt see 1/48 on a hpx300 while shooting 1080 24p

Martti Ekstrand
02-13-2010, 01:46 AM
Please, everyone, learn from this. Fluorescent, HMI, mercury vapor, sodium vapor -- they all interact with CMOS sensors to create these bands, and the only way to get rid of it is to set your shutter speed to match the power frequency of where you live.

Spread the word, so people see this BEFORE they run into a situation where they have ruined footage.

If you're using a CMOS camera, in the US or other NTSC territory, set your shutter speed at 1/60th and just leave it there. Don't go for 1/50th, don't go to 1/48th, leave it at 1/60th.

If you're in a PAL territory, use 1/50th, and only 1/50th.

I'd sticky this info at all the HDSLR forums.

Barry_Green
02-13-2010, 12:17 PM
But it's not just HDSLRs that are affected. ANY CMOS camera, including the Red One, will exhibit the same effect. EX1, HPX300, HMC40, they all do it.

And the CCD cameras have a different artifact that happens in similar circumstances -- they'll execute a cycling white balance shift (or, well, that's what it looks like) if you go changing the shutter speed.

Basically we need to get everyone to glue their shutter speeds on 1/60 (or 1/50 for PAL) and just never change it ever. :)

J Davis
02-13-2010, 03:54 PM
What about multiples of that freq? Like if you are shooting 60p at 1/125 you still stay at 125 right?

thebullfrog
02-14-2010, 07:33 AM
so yeah i did some tests yesterday, what barry says is correct.

I shot (image not video) someone waving back and forth with High speed mode on, with shutter at 1/200, iso 2500, Fstop 1.8 (50mm lens).

It does essentially cycle through a yellow to white balance look. i only got 1 clear image, the rest either had a yellow "hue" or partial yellow/WB.

I checked the other shots from day before and it does indeed have some hue to them.

@shaocaholica : yes if you're shooting indoors with fluorescent lights, if you set your shutter to more then 1/60, and your iso isn't that high....it's very very clearly visible...At 1/125, ISO 1000, you can clearly see it.....no if you're outdoors.

I think, correct me if i'm wrong barry, the reason why theres that cycle of yellow to wb, is because fluorescent lights flickers, and the camera sensor can't read it properly?.

Although for some shots i set the shutter to 1/200 with iso 3200 (high speed on) and it pretty much blocked out the rolling cycle...all the shots were ok..no yellow hue. The reason i did this was to get clear stills of people jumping, no blurry shots (i was at a gymnastics gym).

I'm still playing around with the camera and getting used to taking the images on time, i've since gotten better...so now i don't need the shutter at 1/200 and keeping it at 1/60 (and never changing it) as barry suggests.


Please, everyone, learn from this. Fluorescent, HMI, mercury vapor, sodium vapor -- they all interact with CMOS sensors to create these bands, and the only way to get rid of it is to set your shutter speed to match the power frequency of where you live.

Spread the word, so people see this BEFORE they run into a situation where they have ruined footage.

If you're using a CMOS camera, in the US or other NTSC territory, set your shutter speed at 1/60th and just leave it there. Don't go for 1/50th, don't go to 1/48th, leave it at 1/60th.

If you're in a PAL territory, use 1/50th, and only 1/50th.

Everyone follow the barry's advice...do spread it around.


What about multiples of that freq? Like if you are shooting 60p at 1/125 you still stay at 125 right?

I believe its only if you're indoors that have "Fluorescent, HMI, mercury vapor, sodium vapor" lighting...esp fluorescent...you need to keep it at 1/60. If ur filming at 1/125, 60p...you should still see it.

PaPa
02-14-2010, 07:42 AM
Hmm, interesting. will try plugging in one of my cool light fluorescent fixtures and look to see if these crawling line appears.

Michael Olsen
02-14-2010, 07:52 AM
Just to clarify:

Is this something that occurs only on the older magnetic ballast fixtures? Or also on the modern electronic ballasts? I was shooting under electronic ballast daylight balanced high CRI fluorescent shop lights just the other day and test footage was clean at 30, 40, 50, and 60 FPS at 1080p. I didn't see any banding or color problems (aside from a slight green spike, but that is to be expected as there was no gel applied).

Obviously, if you can't take a look at the ballasts, it makes sense to default to the standard frequency (NTSC 60Hz), but it does seem that there is a technical difference between the two that does produce different results.

In my limited understanding and experience, fluorescents produced for cinema production use electronic ballasts and don't flicker like many "office" fluorescents do. The same principle, unless I am mistaken, applies to HMIs - older magnetic ballast models required shooting at "HMI safe" speeds, while modern electronic ballast models don't require that. Or am I just totally off base here?

thebullfrog
02-14-2010, 08:18 AM
Just to clarify:

Is this something that occurs only on the older magnetic ballast fixtures? Or also on the modern electronic ballasts? I was shooting under electronic ballast daylight balanced high CRI fluorescent shop lights just the other day and test footage was clean at 30, 40, 50, and 60 FPS at 1080p. I didn't see any banding or color problems (aside from a slight green spike, but that is to be expected as there was no gel applied).

Obviously, if you can't take a look at the ballasts, it makes sense to default to the standard frequency (NTSC 60Hz), but it does seem that there is a technical difference between the two that does produce different results.

In my limited understanding and experience, fluorescents produced for cinema production use electronic ballasts and don't flicker like many "office" fluorescents do. The same principle, unless I am mistaken, applies to HMIs - older magnetic ballast models required shooting at "HMI safe" speeds, while modern electronic ballast models don't require that. Or am I just totally off base here?

I'm at work right now, in the office and we have fluorescent lights. I tested (only viewed on the lcd screen, didn't take any footage or images) went through all the shutter settings and different ISO's and it did not produce the yellow bands/colour hue.

So i assume we have the new models and not the older...which is probably where the problem lies.

It's probably the older fluorescent lights that produce these results.

J Davis
02-14-2010, 08:31 AM
I believe its only if you're indoors that have "Fluorescent, HMI, mercury vapor, sodium vapor" lighting...esp fluorescent...you need to keep it at 1/60. If ur filming at 1/125, 60p...you should still see it.

Shooting s1/60 at 60p is not something anyone should do and I'm sure this is not what you are suggesting. Optimum shutter for 60p is 1/120 but the 7D only allows 1/100 or 1/125. Very interested to know which one people advise.


Just to clarify:

Is this something that occurs only on the older magnetic ballast fixtures? Or also on the modern electronic ballasts? I was shooting under electronic ballast daylight balanced high CRI fluorescent shop lights just the other day and test footage was clean at 30, 40, 50, and 60 FPS at 1080p. I didn't see any banding or color problems (aside from a slight green spike, but that is to be expected as there was no gel applied).

Obviously, if you can't take a look at the ballasts, it makes sense to default to the standard frequency (NTSC 60Hz), but it does seem that there is a technical difference between the two that does produce different results.

In my limited understanding and experience, fluorescents produced for cinema production use electronic ballasts and don't flicker like many "office" fluorescents do. The same principle, unless I am mistaken, applies to HMIs - older magnetic ballast models required shooting at "HMI safe" speeds, while modern electronic ballast models don't require that. Or am I just totally off base here?

I too am interested in new ballasts especially for HMI Pars.

thebullfrog
02-14-2010, 08:56 AM
Originally Posted by thebullfrog
I believe its only if you're indoors that have "Fluorescent, HMI, mercury vapor, sodium vapor" lighting...esp fluorescent...you need to keep it at 1/60. If ur filming at 1/125, 60p...you should still see it.

Shooting s1/60 at 60p is not something anyone should do and I'm sure this is not what you are suggesting. Optimum shutter for 60p is 1/120 but the 7D only allows 1/100 or 1/125. Very interested to know which one people advise.

i think the still image i posted up earlier was from a 1080 30p set to 1/125 (somewhere around there...i'm unsure, don't remember the iso)

The footage i took yesterday, it was set to 1/60, ISO 1250 720 60p and it turned out well...no yellow bars/hue

i kept it at 1/60 so as to not produce the problem we've been talking about.

Michael Olsen
02-15-2010, 07:29 PM
Anybody?

PaPa
02-15-2010, 07:31 PM
oh, sorry, forgot to do a test. Will try to remember tomorrow.

PaPa
02-16-2010, 09:24 AM
Just set up my cool lights fluorescent fixtures and glad to say no flicker, waving line, climbing line, or anything of the sort shooting at 1/30th, 1/40th, 1/50th, 1/60th, 24p.

so be worry free.

Barry_Green
02-16-2010, 09:50 AM
The way to know whether you're going to have a problem is to try a fast shutter speed. Try 1/250th or 1/500th. If you have no issues at those fast speeds, you won't have issues at any speed.

Michael Olsen
02-16-2010, 10:33 AM
Thanks, Barry. I'll have to give that a look tonight.

PaPa
02-16-2010, 11:24 AM
Went back and tested again

NO yellow bars of any kind at 1/200th, 1/250th 1/500th or any other shutter speed

Barry_Green
02-16-2010, 12:55 PM
Then yeah, those particular lights are using a high-frequency electronic ballast, and you therefore should be safe using any shutter speed or frame rate with them.

PaPa
02-16-2010, 01:42 PM
God bless Cool Lights and Richard.

thebullfrog
02-19-2010, 07:42 AM
So i did a couple small tests yesterday at my gym. They have the older model ball-set fluorescent lights, so it flickers alot.

In video mode anything higher then 1/60 shutter, definitely shows those yellow bars, higher up you go it's clearly visible.

At 1/60, it's feint, you can just see it a little bit but not a big problem, i just up the iso just a tad bit and its fine and its not noticeable at all.

In picture mode, single shooting 1/60 it's fine if you time your shots....but i'm at a gym where we do lots of gymnastics, and at 1/60 the persons movement gets really blurry and i don't want that.

So i tested out the shutter, Fstop and iso settings and found at 1/125, iso 1000-2000, Fstop around 2 (given i was using a 50mm 1.8 lens) nothing shows up and its a clear non-blurry image (single and high speed shooting)...though its not a perfect still image of the person, theres a little blurriness but still looks good.

Anything lower or higher the 1/125, and the flicker from the lights is apparent...gives it a yellowish hue.

Shooting under an older model ball set fluorescent lights is a pain...but nothing i can do about it.

i'll post some stills in a while showing my findings.

thebullfrog
02-19-2010, 08:03 AM
Excellent videos from rhervag in the 7D Unknown Artifacts (pg 2) (http://www.dvxuser.com/V6/showthread.php?t=200267&page=2) thread


yes for us from PAL land, there really is not much viable option besides 1/50 at all. even 1/100 is problemeatic on fast ballast type of lights.
there is this bar with tri-colored 12V leds that would strobe at every shutterspeed available on the 5D because it is 30p while it is perfectly fine with the 7D at 25p.

some tests from 50Hz ligths

http://vimeo.com/4972364

http://vimeo.com/4991966

Though he's in europe so it's different shutter settings due to pal, but still useful for NA NTSC.

I'm gonna try to do the same type of test in a few days, but with NTSC settings.

mcvideo
02-19-2010, 08:49 AM
appreciate the tests.

Lez
02-20-2010, 01:57 PM
What would be the equation if you were filming with a Pal camera in the USA... and visa versa...

I guess the equation would also relate very closely to 24fps. situation??

Cheers