Pretty complicated issue regarding color spaces

F

FelixGER

Well-known member
Hi,

I have a question regarding the best possible workflow to edit and render AVCHD Files.

Let´s start with my current workflow.

I always colorgrade and render in 32-bit float mode for obvious reasons. But that´s a little tricky in Vegas due to the computer-RGB and Studio-RGB "thing"

1. When I import a AVCHD File from my GH2, from my NX5 or files from the FS100 I downloaded, they are shown with correct contrast in the preview and histogram when I set the project to 8-bit

http://www.imagebanana.com/view/ixpsz2xy/8bitavchd.jpg
Histogram: http://www.imagebanana.com/view/jinbbr9f/8bithisto.PNG

2. Let´s say the editing is now over. I want to set the project to 32-bit float to CC it and render. Now this happens

http://www.imagebanana.com/view/0kp175i9/32bitavchd.jpg
Histogram: http://www.imagebanana.com/view/t0nn5z5q/32bithisto.PNG

The picture gets way to contrasty, both in the preview monitor and the histogram. Whites blow out, blacks crush

3. Solution: I apply the "Levels" Filter "Computer RGB to Studio RGB" (as first filter:IMPORTANT)

http://www.imagebanana.com/view/b114avn8/32bitrgbfilter.jpg

Now the picture again looks like the original 8 bit. Yehaa!

4. Ok, now I colorgrade it to my eye but the Vegas preview Monitor shows 0-255 instead of 16-235 so there a problems incoming

5. I render out to cineform to send the file to my mpeg2 encoder

6. Ups, the file looks way to contrasty (in WMP and the DVD) because it´s not graded for 16-235 but 0-255. Ok, so before rendering I apply ANOTHER "Computer RGB to Studio RGB" Filter to all timelines. The files look now identical to the Vegas preview. JESUS!

------------------------------------------

I can convert all AVCD Files to cineform at first, so the AVIs when imported in Vegas don´t change contrast when changing 8-bit to 32-bit float. (I don´t know why, though)
So I don´t have to do step 3. But that means an unnecessary rendering before editing, like converting to prores for the apple victims.

So my question is: Does this "double level filtering" degrade the image or is this the way to go?
 
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Don't you have to remove the first "computer RGB to studio RGB" before you render out to cineform? This would be between steps 4 and 5. It is like adding a LUT to your footage in Vegas that needs to be removed before you render to end up with the proper output.

If I'm not mistaken, adding another "computer RGB to studio RGB" just reverses the first one.

If someone can clarify, confirm or debunk my thinking here it would be greatly appreciated :)

Cheers,
Pete
 
No. Adding another one (the same) just flattens the image even more.
To reverse it, you would have to add Studio RGB to Computer RGB.

Adding the Computer to studio RGB in step 6 is usual with vegas since it gives you a 0-255 preview.
But what I don´t get is the alteration of the footage, when you switch from 8 bit to 32 bit float (2.222 Gamma)

Cineform files don´t change contrast. AVCHD MTS files do...
 
Sorry for the confusion. I'm going through the same issue to get Blu-Ray output to match my display for editing and have had to do something similar to what you are going through.

First is to look in Vegas under Option - Preferences - Preview Device and see if "Use color management" and "Use Studio RGB (16 to 235)" are checked? This will bring your display closer to WYSIWYG on DVD or Blu-Ray output. You don't want to check those if your output is computer based for Youtube or Vimeo.

Second I believe you want to use "Studio RGB to Computer RGB" to adjust your display for editing AVCHD directly if your playback device is 16-235. Then remove this filter before rendering. This will give you a very contrasty crushed image for editing. Exactly what converting from your AVCHD 0-255 to broadcast 16-235 will give in the final output.

Thirdly there may be an issue with the NTSC 7.5 IRE pedestal if you are by chance shooting with some strange NTSC cam setting and going to PAL. We'll have to research that one some more as I know there can be some issues there as well.

Here's one link to where I've found some of this info: http://techblog.cineform.com/?p=2959

Why their (cineform) transcoded clips don't do it while the AVCHD clips do is confusing to me. All I can think of is that cineform is 10bit 4.2.2 color space and probably in the legal broadcast range to begin with while the AVCHD clips are 8bit 4.0.0 and not completely in the legal broadcast range.

Anyway more food for thought.

Cheers,
PEte
 
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c3hammer said:
Sorry for the confusion. I'm going through the same issue to get Blu-Ray output to match my display for editing and have had to do something similar to what you are going through.

First is to look in Vegas under Option - Preferences - Preview Device and see if "Use color management" and "Use Studio RGB (16 to 235)" are checked? This will bring your display closer to WYSIWYG on DVD or Blu-Ray output. You don't want to check those if your output is computer based for Youtube or Vimeo.
Click to expand...

This does not change my preview at all.


c3hammer said:
Second I believe you want to use "Studio RGB to Computer RGB" to adjust your display for editing AVCHD directly if your playback device is 16-235. Then remove this filter before rendering. This will give you a very contrasty crushed image for editing. Exactly what converting from your AVCHD 0-255 to broadcast 16-235 will give in the final output.
Click to expand...

Yep, that´s just a different approach for step 6. But doing it that way means I don´t have a flat image to grade. That´s just unusual for me.

I think I just keep converting everything to cineform. Maybe that´s better to grade with anyway

There is another very weird thing.
When I directly export mainconcept mpeg 2 DVD from vegas a 0-255 grade looks fine in WMP and on my TV when playing the DVD. Same with Sony AVC and Bluray. Only the cineform export looks different from the preview monitor and needs to be "leveled" to 16-235
 
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Well, it seems to me that you should just skip Cineform. I don't really think it's adding anything to your workflow.
 
Sorry,I think you didn´t read my issue properly.

The first Cineform conversion is a benefit because 8 bit and 32-bit project settings then look identical.
But I really like to skip that. Directly work with AVCHD. But ingesting AVCHD in Vegas on a 32bit timeline results in a "destroyed" imagewith to much contrast and gone information in the highlights and shadows

The second Cineform conversion is just to get a master file out for external encoders.
 
Which version of Vegas is this? If it's Vegas 10, you can use the 32-bit floating point (video levels) option and AVCHD doesn't change.
 
AVCHD may not work in the demo version due to licensing issues. But at least you'll be able to see the option in the drop-down menu.
 
Yep, that was correct.

But I tested 32bit Videolevel in Vegas 9 and it also works!

AVCHD now behaves like cineform files.

Even when rendering out, there was this issue that cineform changed contrast but Sony AVC and Mainconcept Mpeg2 did not.
I think, that´s because cineform always decodes to studio rgb but 32 bit full range with the implemented sony codecs decodes to computer RGB


Now they all change contrast, just like 8-bit rendering. One Computer-to-Studio RGB filter before rendering (which is normal in vegas) and that´s it. Perfect.
That´s the solution to all problems! :)

Can you explain the difference between 32 bit videolevel and 32 bit full range?
Is the a downside of using videolevel when working with an 8-bit source?
 
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Didn't know if V9 had it or not; I never had V9. I skipped it.

(video levels) keeps you in the video RGB range, eliminating the problem you were encountering.

Check out Glenn Chan's website; he goes into a lot of detail about all sorts of things having to do with color and Vegas.
 
FelixGER said:
Let´s say the editing is now over. I want to set the project to 32-bit float to CC it and render. Now this happens
Click to expand...

...Have you tried editing with your project set to 32-bit float ( video levels ) ?

Normally I start with my project set to 32-bit float ( video levels ), and I grade in the same color space. No problems at all.

For work that I am archiving, bringing in to another program, or sharing with a Final Cut Pro person, I then export as a Cineform AVI.
 
Felixger, I shoot AVCHD and never have used the 32 bit float. Just so I can be sure I understand the conclusion of this thread, could you list your newly revised workflow steps? I'd like to give it a try in Vegas 10.
 
Alright

1. Import AVCHD, Cineform or Prores with correct project settings
2. Edit in 8-bit for better speed
3. Switch to 32 bit Videolevel
4. Apply the Levels Filter "Computer RGB to Studio RGB to all clips. This has to be done now because the filter must be the first effect. When you apply it as the last one, the contrast will be wrong, too flat
5. Deactivate filter before you grade a clip
6. Colorgrade
7. Activate filter
8. Render

That´s what I´m currently doing but I´m testing if there is a more efficent way.


Edit: ...AND found one.

Main problem is -as stated above- that applying the levels filter last or on the timeline will not result in an identical picture when playing the file in WMP and looking at the vegas preview. When apllying the filter at first, the result is more similiar but still not the same and the workload when you want to deactivate all filters is not acceptable. So I altered the filter setting using a high contrast scene.

http://www.imagebanana.com/view/5kasp6nc/EinstellungVegas.jpg

When you take the Computer-to-Studio RGB Filter and modify it like in the screenshot, you will be able to apply this filter to the timeline, getting a file that looks similar to the Vegas preview. (Except for colours. Vegas preview is always more saturated than WMP, I don´t know why)

So, the final workflow is:

1. Import AVCHD, Cineform or Prores with correct project settings
2. Edit in 8-bit for better speed
3. Switch to 32 bit Videolevel
4. Colorgrade
5. Apply the "special" Computer-to-Studio RGB Filter to all videotracks
6. Render

Maybe this modified filter can be twaeked even more but I think it´s about 95% correct
 
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Hi, my first post.

I recently got Vegas myself. I edit AVCHD files from the GH2.

As far as I understand the MTS files are recorded in sRGB, meaning values 16-235 (correct me if I'm wrong), so Vegas 32bit float video levels seem fine to me.

But when you work in FULL RANGE 0-255 Vegas defaults to a linear gamma of 1, not the sRGB standard of 2.22. But there is a pulldown menu in the program so that you can chose 2.22 gamma in full range too.

But I have read that if you want to do better compositing effects in Vegas you should work in full range mode with a 1.0 gamma.

Maybe this gamma thing in full range mode is what the problem was?

BTW, I use Vegas Pro 10.
 
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