Black Levels when rendered at DVinfo.net

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Canon VIXIA Series AVCHD and HDV Camcorders
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Old January 15th, 2007, 05:57 PM   #1
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Black Levels when rendered

Hi chaps

just wondered if anyone can shed any light on this problem
When I take a m2t into vegas and render as wm9 (or any mpeg4 but not mpeg2, DV etc) the output is brighter / greyer than the original.

Here is an example where the original m2t background was completely black but on my system this wmv shos as grey. I had a play with the ATI control centre and it appears I can control the brightness from there in overlay mode?

http://www.filefactory.com/file/a3e8bd/ (5mb)

Does anyone else see this as grey by default?

Cheers
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Old January 16th, 2007, 11:06 AM   #2
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Anyone? I am happy to provide the original m2t if required?

I do find it very difficult to know which method to use when filming in low light to prevent gain. Only the spotlight mode seems to work but that requires lots of light (not sure if its also reducing shutter to 25) In P mode reducing the exposure also works but focus / sharpness is lost. Auto mode is a definite no!
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Old January 16th, 2007, 01:27 PM   #3
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Fergus,

Color looks right to me played back in WMP11. Although I have experienced the issue you are talking about.

Brian
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Old January 16th, 2007, 02:07 PM   #4
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Possibly the MPEG4 and WMx codecs are using the wrong range for black to white. This can be especially true if these codecs require RGB input (rather than YUV). There's a lot of incorrect programming out there that confuses gamma-corrected RGB (often termed R'G'B') and standard RGB. If the codec assumes the wrong flavour of RGB, you can end up with greyer than expected results (or the reverse).
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Old January 16th, 2007, 04:26 PM   #5
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Thanks John - I tried the studio RGB preset in Sony Vegas Level filter and the output looks much better

My concern however was if it was just my system - ie will the studio rgb version that looks ok on my machine look too dark on another and will the default for me which is grey and too bright be correct for others?

Brian its intersting that for you it looks right - here is the original to compare with:
http://www.filefactory.com/file/d068aa/
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Old January 16th, 2007, 08:06 PM   #6
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QT conversions I'm doing also exhibit that brighter slightly more washed out look.
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Old January 17th, 2007, 05:01 AM   #7
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It can also be your output player or videocards overlay settings that cause the hubbub. This is very annoying indeed.
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Old January 17th, 2007, 05:20 AM   #8
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(wow, 1st post)

Hi Fergus,

The confusing thing is that you can often set Studio RGB for encoding and previewing seperately. Also, overlay settings and other display driver settings may indeed alter display. Finally, codecs may indeed tamper with levels, so a post render check is always a good idea...

I took your sample into my NLE-app and measured a Studio RGB blackpoint in the file: RGB(16,16,16). So: there is no black in your file, the darkest is grey. If you also have the Studio RGB previewing option on, you'll end up with RGB(31,31,31) on your screen. And who knows what the display driver may be up to...

With regard to your question what is best for other systems: because of the non-linear response of the various display types (CRT's are the worst, some LCDs tend to blow out high, almost white, values), I think it is generally a good idea to use the limited range of Studio RGB. (Accessable in your Vegas I think through its broadcast colors video effect)

So in my opinion: levels are perfect in the file. :)
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