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Author Topic: Colour Correcting / Balancing AV gear  (Read 1357 times)

Mark Olsen

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Colour Correcting / Balancing AV gear
« on: October 02, 2015, 10:02:47 am »

So, I'll preface this post by saying that I'm mostly a sound guy, but I'm no stranger to pro-photography.

I've started working in a new church environment where we're doing IMAG, video and slide presentations as well as broadcast to outlying venues.
We've got the Black Magic studio cameras and the matching production switcher along with a varying array of fairly large projectors, being run by a combination of SDI and HDMI. Stage lighting for video is all tungsten fixtures, a mixture of PAR 64 and Ellipsoids.

We're struggling to get a consistent picture across the various monitors and projectors. They're close, but we want them to be closer. Some have too much contrast, some have weird color balances and some seem to have strange gamma effects. I've tried to adjust them all by eye, but it seems to be a lot of hit and miss and subjectivity.

In photography world I'm used to using color targets and things like Spyder colorimeters to get accurate display profiles. So I'm used to working with computers and getting them right, but I'm struggling in the video / broadcast context. I'm thinking I'm going to need color targets and a colorimeter but I'm not sure how to then employ them correctly.

I'd love and general pointers you guys have on getting this right, but if you've made it this far, I'd love some specific pointers.

1. How do I use the color targets to match different cameras?

2. How do I get accurate multiview colors, when it comes straight out of the switcher as HDMI?

3. How do I scientifically match projectors? If I use a colorimeter to measure it, how do I apply a color profile to a projector?


Mark
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frank kayser

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Re: Colour Correcting / Balancing AV gear
« Reply #1 on: October 02, 2015, 12:37:08 pm »

So, I'll preface this post by saying that I'm mostly a sound guy, but I'm no stranger to pro-photography.

I've started working in a new church environment where we're doing IMAG, video and slide presentations as well as broadcast to outlying venues.
We've got the Black Magic studio cameras and the matching production switcher along with a varying array of fairly large projectors, being run by a combination of SDI and HDMI. Stage lighting for video is all tungsten fixtures, a mixture of PAR 64 and Ellipsoids.

We're struggling to get a consistent picture across the various monitors and projectors. They're close, but we want them to be closer. Some have too much contrast, some have weird color balances and some seem to have strange gamma effects. I've tried to adjust them all by eye, but it seems to be a lot of hit and miss and subjectivity.

In photography world I'm used to using color targets and things like Spyder colorimeters to get accurate display profiles. So I'm used to working with computers and getting them right, but I'm struggling in the video / broadcast context. I'm thinking I'm going to need color targets and a colorimeter but I'm not sure how to then employ them correctly.

I'd love and general pointers you guys have on getting this right, but if you've made it this far, I'd love some specific pointers.

1. How do I use the color targets to match different cameras?

2. How do I get accurate multiview colors, when it comes straight out of the switcher as HDMI?

3. How do I scientifically match projectors? If I use a colorimeter to measure it, how do I apply a color profile to a projector?


Mark
Mark,
I, too, an familiar with the pro photography end of things concerning color spaces and color matching. Also, not so much av.

A question: the difficulty you're having is matching the various outputs, rather than discrepancies among inputs, correct? 

So, a little speculation here...
To use a color chart or checker, it would seem one must have at least one calibrated monitor - after your switcher.  You would go about calibrating that with a colorimiter much like you would your computer screen.

At that point, you have a input and output that are in sync, color wise.

I know there are colorimiters designed to work with video projectors, and the software will instruct you on what parameters to change on the device (RGB, GAMMA, BRIGHTNESS, CONTRAST, etc.) - providing they are available.  I'm sure something is available like that for dumb CRTs and LCDs.

Video feeds to another device and then to a screen gets more complicated -

Another thing is whether your devices (LCD, CRT, projector, etc) AND THE SOFTWARE are themselves color calibrated.

We went through this in the camera club when competitions started including projected images...
They had a software program written in VBA for judging photos - all tied to Powerpoint.
All well and good, but Powerpoint was not itself color aware. So someone set up their photos with subtle gradations of color viewed in Photoshop were horrified when Powerpoint displayed them with pretty much any old red, green and blue, rather than responding to the actual colors, intensities, etc. in the photo.  BTW, the projector had been calibrated as well, but if the middle piece throws things away, well...

So, for an accurate color corrected presentation, the source, software, and the output device must all be calibrated, and calibration aware.  If there are differing brands of monitors, projectors, etc, getting them all in "perfect" alignment may be a fools errand.

I would find out what the capabilities of the output equipment are, and if you can actually get to the adjustments, work with a colorimiter.

Final thought... Much like a color-matched print will never quite match the flat panel or a CRT, because of the light source - whether light through a semi-transparent matrix, or light reflected off dyes or pigments, I'm guessing that in the same way there will be differences between projected images and monitors. 

FWIW,
frank
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Lee Douglas

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Re: Colour Correcting / Balancing AV gear
« Reply #2 on: October 02, 2015, 01:46:43 pm »

Imaging Science Foundation ( https://www.imagingscience.com/index.php ) would be a good place to start.  The offer a disc with test patterns and other media along with a step by step tutorial to help you calibrate a display device on your own.  They also offer certification for dealers and contact information for those dealers who can come onsite with the proper calibration equipment to set your display up optimally.  What many people don't realize is how much changing one parameter affects the other parameters, when calibrating a display.  Frank has a point though.  You've got calibrate for source.  Many displays offer calibration for each input, but if your running everything through a matrix this may not be an option.
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Jordan Wolf

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Re: Colour Correcting / Balancing AV gear
« Reply #3 on: October 07, 2015, 09:50:11 am »

Mark,

It's a niche subject, but search around for "color shading". Usually, one person will be dedicated to shading via the CCU remote as they watch a waveform monitor and/or vectorscope to ensure uniform brightness, etc. between sources.

How To Match and Balance Multiple Cameras

Color Shading Basics

Color Shading
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Jordan Wolf
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"We want our sound to go into the soul of the audience, and see if it can awaken some little thing in their minds... Cause there are so many sleeping people." - Jimi Hendrix
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