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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 June 4th, 2010, 11:56 PM   #1
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Color Bars for the t2I via jpg

one of those dumb limitations of the cameras is the lack of bars. the simple stupid way of getting them ? creating a new image the exact same size as the images created by the 550D, then taking a standard TGA color bars image, stretch it to fit, save it as a JPG.

the important part - be sure to name it so it matches the camera's image sequence naming convention. I called mine IMG_0001.jpg that way it always sorts to the top.

downside is if you format the card you loose it, but easy enough to copy back to the card. here is the image.
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Color Bars for the t2I via jpg-img_0001.jpg  
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Old June 5th, 2010, 05:35 AM   #2
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Just wondering Steve, why you would need a jpg compressed image of bars on your T2i?


All the Best!
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Old June 5th, 2010, 08:59 AM   #3
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Handy for checking external monitor is set correctly I guess.
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Old June 5th, 2010, 09:22 AM   #4
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Despite of its simple look, SMPTE bars is very sophisticated signal/tool used in television for test and align purpose. Itís not just a bunch of randomly chosen colors, each color serves very specific test/alignment. The reason RGB cameras like yours donít have SMPTE color bars, is because in RGB color space you cannot reproduce all colors that are in SMPTE bars, namely the I and Q color bars. If you convert YUV values of I and Q bars into RGB colors they translate into negative RGB values. Since values for RGB in files like jpeg, tiff, etc. are stored as unsigned (positive) integers, there is no way to store/represent these colors. So, the only usable/meaningful part of that Color bar in RGB color space is the top 7 bars.



You could use somthing like ARIB multi format bars; this bar has no negative RGB values.



But as David asked: why would you need it?
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Old June 5th, 2010, 10:18 AM   #5
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bars are for amongst other things, checking your monitor to see if its anywhere in the ballpark of calibration. if you haven't been burned by a monitor thats adjusted way out... you haven't lived :( no guarantee a LCD/LED monitor is where its supposed to be if some one else messed with it. also since these cameras output composite, you can equally driver CRT's like the sony 13" I still have. bars are good to get a basic sense of if your composite line is good, doesn't have termination problems, ect.

more importantly, bars are good for seeing if your monitor is too bright / dark.

as for RGB / YUV conversion... all I'll say is that these bars that came from a NLE have no problem hitting all the boxes on a real world vector scope... so I'm not too worried.
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Old June 5th, 2010, 06:31 PM   #6
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I tend to have all my gear calibrated before it ever gets to location, so it's not a problem.
And I own a portable SMPTE bar & tone generator for when needed.
As mentioned, there are problems adding bars your way. A more useful solution would be to add a chart/slate to your kit. That way you have an actual accurate through the lens measurement which becomes an asset in post.
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Old June 9th, 2010, 06:56 PM   #7
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taking a new small 7" LED monitor out today, having bars in the camera was useful. this is especially true when needing to adjust it for bright conditions, then going into dark. YUV/RGB conversion is so not an issue for making a _basic_ check that the monitor is somewhere near correct. some folks get very caught up in Nth degree perfection while forgetting that reasonably accurate will do most of the time.

if not bars, then a stepped ramp would be the next most useful item to check monitor adjustment for brightness / contrast.

I've been shooting for 20+ years and I don't have a portable bars generator, they have always come from the camera. there are a lot of simple and practical reasons to do so. shooting bars is modestly useful, but ever since cameras started adding all sorts of DSP processing on the image, I don't think its really relevant anymore. you could have perfect WB and exposure, change the camera from neutral or standard to portrait or landscape and completely skew the bars reading. so between lighting, camera WB and color processing, shooting bars on a shoot is only useful for post... maybe, if your goal is to get to some neutral consistent look. However, that look might not be so interesting.

shooting bars is not useful for checking monitor calibration because its not a fixed reference point like an image file is. you want a fixed reference point like a generator or bars in camera... which is what the file does, even if not Nth degree perfect, its more then good enough for basic adjustment.
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Old June 10th, 2010, 06:54 AM   #8
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Quote:
Originally Posted by Steve Oakley View Post
taking a new small 7" LED monitor out today, having bars in the camera was useful. this is especially true when needing to adjust it for bright conditions, then going into dark. YUV/RGB conversion is so not an issue for making a _basic_ check that the monitor is somewhere near correct. some folks get very caught up in Nth degree perfection while forgetting that reasonably accurate will do most of the time.

shooting bars is not useful for checking monitor calibration because its not a fixed reference point like an image file is. you want a fixed reference point like a generator or bars in camera... which is what the file does, even if not Nth degree perfect, its more then good enough for basic adjustment.
I guess this is where we differ Steve,
I'm a little more anal, so reasonably accurate won't fit.
If you are a working professional you either calibrate your gear to broadcast specs or you don't. It's as simple as that! So for those who care, here are my thoughts.
Adjusting a monitor in the field depending on the ambient lighting conditions will throw your monitor out of calibration every time you do it. Don't!
#1, Set your monitor's calibration at home with the proper gear and then don't touch the controls!
If you are having problems seeing your monitor due to bright light outside then get a hood or shade the monitor, but don't touch the controls.
#2, Purchase the best chart you can afford! Especially with a camera like the T2i which lacks in depth white balance controls. Even if the best you can afford right now is only $36, do it. A $36 chart is better than no chart at all.
I know, I just heard a shout out from the guy that said... Hey we do a 3 man run and gun, 2 HDSLRs and an audio guy but don't want to set up a chart as we change places all the time, what do we do?
Purchase one of the smaller charts or chart set, and fashion a quick mount of your choice like velcro, and attach to the back support of the audio guy's harness.
#3, Take still ref pics before you shoot video to double check your exposure with the histogram on the T2i.

I would challenge other T2i users to try these 3 steps and see if if doesn't make a difference in the finished product you deliver.

All the Best!
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