Black Levels when rendered at DVinfo.net

Fergus Anderson · January 15th, 2007, 05:57 PM

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

Fergus Anderson · January 16th, 2007, 11:06 AM

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!

Brian Engleheart · January 16th, 2007, 01:27 PM

Fergus,

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

Brian

John Miller · January 16th, 2007, 02:07 PM

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).

Fergus Anderson · January 16th, 2007, 04:26 PM

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/

Rich Dykmans · January 16th, 2007, 08:06 PM

QT conversions I'm doing also exhibit that brighter slightly more washed out look.

Mikko Lopponen · January 17th, 2007, 05:01 AM

It can also be your output player or videocards overlay settings that cause the hubbub. This is very annoying indeed.

Pieter Jongerius · January 17th, 2007, 05:20 AM

(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. :)

January 15th, 2007, 05:57 PM	#1
Fergus Anderson Major Player Join Date: Nov 2006 Location: London, UK Posts: 321	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

January 16th, 2007, 11:06 AM	#2
Fergus Anderson Major Player Join Date: Nov 2006 Location: London, UK Posts: 321	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!

January 16th, 2007, 01:27 PM	#3
Brian Engleheart New Boot Join Date: Nov 2006 Location: Hoboken, NJ Posts: 8	Fergus, Color looks right to me played back in WMP11. Although I have experienced the issue you are talking about. Brian

January 16th, 2007, 02:07 PM	#4
John Miller Major Player Join Date: Oct 2005 Location: Hillsborough, NC, USA Posts: 968	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).

January 16th, 2007, 04:26 PM	#5
Fergus Anderson Major Player Join Date: Nov 2006 Location: London, UK Posts: 321	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/

January 16th, 2007, 08:06 PM	#6
Rich Dykmans Regular Crew Join Date: Dec 2006 Location: Discovery Bay, CA Posts: 138	QT conversions I'm doing also exhibit that brighter slightly more washed out look.

January 17th, 2007, 05:01 AM	#7
Mikko Lopponen Major Player Join Date: Mar 2006 Location: Helsinki, Finland Posts: 393	It can also be your output player or videocards overlay settings that cause the hubbub. This is very annoying indeed.

January 17th, 2007, 05:20 AM	#8
Pieter Jongerius Regular Crew Join Date: Jan 2007 Location: Netherlands Posts: 101	(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. :)