Eternal color space dilemma, your workflow?

essami wrote on 5/23/2011, 5:13 PM

Hi!

Yep, still after years with Vegas Pro 10 I'm asking the same question! :) I'm still unable to wrap my head around this problem and would like to try and make sense of it to myself once and for all!

I've created a workflow that works with DVD and web based video delivery but lately I've had to deliver videos to be transferred to Digibeta and Blu-Ray. But let me explain my workflow as it stands now:

1) I bring my footage (Red One or Panasonic GH1) to Vegas Pro 10
2) I color correct
3) I render to WMV and upload to Vimeo and Youtube
(This is very simple so I use this for all my personal projects)

or

1) I bring my footage (Red One or Panasonic GH1) to Vegas Pro 10.
2) I color correct and apply Sony Levels FX with computerRGB to Studio RGB preset
3) I render to AVC or MP4 / Mpeg2 and upload to Vimeo or Youtube / or burn a DVD
(This method is I use if I need to provide a client who uses a Mac or needs a DVD)

So this works and I get the results I'm after. Now my problem is that I still don't fully understand what I'm doing. I've read the Glenn Chann tutorial about 100 times all the way through but it's just not clicking for me. Partly because english is not my mother language but also there's a few fundamentals that I'm not fully understanding. So! The questions:

A) How do I find out what codec decodes to which color space? Do I take the footage to Vegas and look at the histogram. If it goes below 16 and above 235 I can say "this is cRGB?" If not I can safely assume it's sRGB?

B) The codec doesn't always decode the same way right? If I play it in Quicktime Player or if I put into Vegas it can look different, so does this mean the player/NLE has a setting for how it decodes the color space? Or is this random?

C) But even if it doesn't always decode the same way it still fundamentally is in the same color code no matter what? The player/NLE just decodes it wrong or correctly and this is something one just needs to know?

D) Do I really need to know how my client will be using the file I'm going to provide to him? I've sent files to TV stations and they've been broadcast in the wrong color space. I want to learn to make sure this doesnt happen because of what I've done.

E) An example: I need to send a Quicktime file with DXnHD codec to a client. Original footage was shot with Red One camera. Workflow: R3D files imported to Vegas Pro 10. Color corrected. Rendered out to Quicktime DXnHD. The rendered file looks good viewed with quicktime player and it looks the same if I import the rendered file back to Vegas. The files look like they are all in cRGB mode, blacks go below 16 when I look at the Vegas histogram and whites go above 235.

What can I expect if the client decides to put it in a Mac NLE and put to Digibeta for screening. How about if they decide that they're just gonna render it to a DVD and project it from that? How do I take this into account?

Phew. You guys have helped me so much throughtout the years it's unbelievable, I aks your help once more! What I would really appreaciate is to go through this step by step if anyone has the patience for that :) I need to understand things bit by bit and once I understand a few fundamentals I'm sure the big picture will reveal itself to me!

Thank you!

Sami

Comments

musicvid10 wrote on 5/23/2011, 5:59 PM

Sami,
That's a lot of questions, and I don't know that there is a single set of answers for all the possible combinations you listed.

The places where unwanted or deliberate changes in levels can occur include the shoot and codec, decoders, encoders, and players. That's a lot of places for some thing or another thing to change. One codec that you mentioned WMV, is notorious for not behaving the way one would normally expect.

Best thing to do is actually shoot a grayscale (I like the old Macbeth Color Checker) with the footage, so you can see visually how it holds up throughout the workflow. Also, placing a grayscale image on the timeline will give you something you can scope through different iterations or porting to another OS.

I suspect by the time you are done, you will have developed several workflows that will serve different purposes, and that others will benefit from.

Here's a free grayscale I designed just for HD work in Vegas.
It will tell you instantly if you are getting unwanted levels conversion at any point in your workflow:
http://dl.dropbox.com/u/20519276/dualgray1.png

farss wrote on 5/23/2011, 7:21 PM

For me the most fundamental thing is looking at the waveform monitor. Cameras today can record in three different ways:

1) Y' = 16 to 235 What video camera should have recorded to.
2) Y' = 16 to 255 What video camera do by 'accident' and increasingly by design
3) Y' = 0 to 255 Mostly the vDSLRs record this way.

Other thing worth knowing, Vegas decodes Y'CbCr to the same values, no clipping will take place. Most other NLEs do not work this way and will clip anything outside "legal".

Tape formats such as DigiBeta should be recorded with legal levels but they will preserve values outside legal.
DVDs are the same except the players will generally clip anything illegal. So if you don't want your blacks and white clipped or a DB tapes rejected keep things legal.

So my workflow is to look at what I'm working with if I don't know for certain and my goto tool is the waveform monitor. I have no hard and fast workflow. I work from what I have preserving as much of it as possible and then using the video buss conform it as needed via a Color Curve although you could just as easily use the Levels FX.
I also have an old CRT that's in a reasonable state of calibration as a visual check. Hopefully this week I'll add a decent HD LCD monitor.

Bob.

essami wrote on 5/24/2011, 3:11 AM

Thanks guys! You are definately helping here, I'm slowly getting there!

I use the Vegas preview window to preview. Theres the IRE 7.5 button and the RGB 16-235 button in the video scopes settings. This will change how the histrogram shows the values right?

So how have you guys set it up? And how would you recommend me to set it up for myself since you know I'm previewing and color correcting on my computer screen and not using an external monitor.

Sami

Rain Mooder wrote on 5/24/2011, 5:26 AM

Aside from the 0-255 versus 16-235 levels issue which I'll get to in a moment, what
you color correct to is what your space is.

If you pull a bunch of Red material on to the timeline and then color correct it using
an sRGB calibrated computer monitor, your colorspace is for all intents and purposes
sRGB. You can feed that out through whatever plugin to Vimeo and it is going to look
great provided you and vimeo agree on the 0-255 versus 16-235 thing.

If you watch this video on a TV monitor (or send DNx to a TV station) the colors are going to be wrong AND the levels too contrasty. The colors will be wrong because the monitor wants REC709 and you did not color correct to make the video look good in RED709. The video will ALSO look too contrasty because vimeo loves sRGB packed into 0-255 RGB and TV loves REC709 packed into 16-235. Even if you do a levels change from 0-255 to 16-235 though, the colors are still going to be wrong because sRGB is not REC709.

If you want to render to broadcast and the web and keep all of the colorspaces honest,
here is one strategy. Get a decent SD broadcast monitor off ebay like a sony PVM and
plug it into a bmd intensity pro. Do all of your color correcting on the sony PVM monitor
and keep your levels legal (16-235). Render out the DNxHD and mail it to the TV station.
You have just sent them legal REC709 with (16-235). Next, load up adobe after effects
and use their color conversion utility filter to do a colorspace conversion from REC709
to sRGB. You will now have honest 0-255 sRGB that has proper colors. If you don't have
AE or want to stay in vegas, drop a second color correction filter on your timeline
and stretch the 16-235 up to 0-255 and add a bit of saturation back in. This won't be
a perfect rec709 to sRGB conversion but it may be good enough for your task.

Again, which codecs render what to 0-255 and 16-235 is not the important thing. The
important thing is how you color corrected the footage.

farss wrote on 5/24/2011, 6:53 AM

"Theres the IRE 7.5 button and the RGB 16-235 button in the video scopes settings. This will change how the histrogram shows the values right? "

Yes. I have the 7.5 IRE unchecked and the Studio RGB checked.
With that setting I know my blacks should just kiss 0 and the white peaks 100, assuming of course they are any in the current frame. Of course I may have to spool through a fair amount of footage to determine that.
In general though I can be quite confident in knowing that the cameras I mostly use will go from 0 to 109. Any still images from a DSC or my scanners will go from -9 to 109.

" And how would you recommend me to set it up for myself since you know I'm previewing and color correcting on my computer screen and not using an external monitor."

If you're trying to do half decent color grading an external monitor from my experience is kind of mandatory. I'm yet to get much joy out of the cheaper "computer" monitors and typically a monitor used for general computer use should / could be setup differently to one used for evaluating video.

Personally if I was spending the kind of money it costs to shoot on a Red One I'd be wanting to look at the footage on a fairly decent monitor that was reasonably well calibrated. I'm only talking about spending less than what a Red One and a set of primes costs to rent for a day.

Bob.

musicvid10 wrote on 5/24/2011, 8:00 AM

The checkboxes do NOT affect the histogram.
They change the colorspace of the Waveform.

I leave both boxes unchecked, preferring to see the Waveform report the levels in the scene, the same as the Histogram and Parade, and not expanded.

I believe the 16-235 switch was originally there for MS DV files, which misreported their true output levels.

essami wrote on 5/24/2011, 9:05 AM

Bob, thanks for the advice! Thats the default settings that I use as well. I'll stick with that.

I understand what you are saying about the need for external monitor. I'm on a small budget and will have to hold off for the moment unfortunately. So far I've been lucky enough to be able to shoot with the Red One for free on occasion. Music video projects in Finland are extremely low budget and we can barely afford to rent out lights.

But that said I've actually never had a problem with color correcting on the computer screen. Only problems I've had so far have been with blown higlights and washed out blacks due to this color space issue being so problematic and confusing.

Check out a few of my work here: http://www.vimeo.com/essami

Sami

Rain Mooder wrote on 5/24/2011, 12:39 PM

<partial retraction> I just read that Youtube and Vimeo do some sort of auto
16-235 to 0-255 extraction. I run my own hosting so I missed this important bit.

If all Youtube and Vimeo is doing is the contrast stretch then life is a bit
more complicated. If you have REC709 that is 16-235 you need to do color
conversion in AE from REC709 to sRGB 0-255. Then you have to drop the
contrast down to sRGB 16-235/this weird cRGB thing. At any rate, cRGB 16-235
is still not REC709 16-235 so the colors are going to be slightly different
colorimetry.

Depends on what you want to look right. If you want to web to look better than
broadcast than do everything in sRGB or cRGB on an LCD. If you want broadcast
to look right then REC709 on an external monitor etc....

essami wrote on 5/24/2011, 3:26 PM

Yep thats true about Youtube and Vimeo.

This is also a good thread to read on this: http://www.sonycreativesoftware.com/forums/ShowMessage.asp?MessageID=764042&Replies=14

I myself dont mind if the colors are slightly off. They will be most likely off a bit anyways because of the different settings on televisions, projectors etc. What I do mind is my darks being washed out and whites being clipped.

amendegw wrote on 5/24/2011, 4:33 PM

"<partial retraction> I just read that Youtube and Vimeo do some sort of auto 16-235 to 0-255 extraction. I run my own hosting so I missed this important bit."I'm a little late to join this discussion, but in our testing, we also see this idiosyncrasy in all locally hosted flash players tested.

First, I give credit to Nick Hope for this. A test Vegas project is located here: NickHopeLevels.zip The project uses Generated media to create panels of 235, 245, 255 white & 0, 8 & 16 black. As you can see in the Vegas Preview, shades of white & black are visible.

However, when rendered to an h.264 (mp4) and played with JW Player, the panels are all seen as black (255) or white (0). Click here for an example.

...Jerry

farss wrote on 5/24/2011, 4:55 PM

Musicvid said:

"I believe the 16-235 switch was originally there for MS DV files, which misreported their true output levels."

My understanding is that the waveform monitor attempts to report levels the same as a hardware waveform monitor would which is why it's scaled according to IRE levels. Roughly eyeballing the signal on a hardware scope and the waveform monitor in Vegas set to "studio" they're close enough. I've even more roughly checked this with XDCAM EX from the HD SDI output of the camera and looking at the decoded output in Vegas they're close.

Of course all of the above is technically a bit of a crock. All that Vegas is working with are binary numbers that don't have any dimensions whereas a true waveform monitor is reading volts and using a defined stardard to convert volts to "IRE" levels. With HD SDI the system is digital but again there is a defined set of standards.

The RGB parade displays the binary values and is scaled accordingly. It isn't concerned with even trying to emulate what the image would look like on a hardware device. This is probably why the Computer / Studio RGB switch has no effect on it.

If I put the 0 to 255 linear gradient onto the timeline the RGB parade displays 0 to 255 which is correct, that's what the generated media is set to. Looking at the waveform monitor set to Studio RGB it shows levels that are illegal going from 109 to -8 which is what I'd anticipate if I printed that to tape as is.

Of course all of this is purely a matter of personal choice. So long as you know how to interpret what you're looking at it matters naught. The only bit that caught me eye was "preferring to see the Waveform report the levels in the scene". With the waveform monitor set to Computer RGB and Luminance it is not showing the levels in the scene. The blacks will read as not being black for DV and HDV etc. The only time it correctly read the levels in the scene is if the footage was shot with a vDSLR or if it was a still pulled from DSC.

Bob.

farss wrote on 5/24/2011, 5:02 PM

" At any rate, cRGB 16-235 is still not REC709 16-235 so the colors are going to be slightly different colorimetry."

Possible source of confussion here is that "sRGB" is an Adobe defined colorspace. What's really being talked about here is not "color space" at all, only the luma component. All the issues regarding primaries etc are left for another day, thankfully.

Bob.

musicvid10 wrote on 5/24/2011, 6:36 PM

"If I put the 0 to 255 linear gradient onto the timeline the RGB parade displays 0 to 255 which is correct, that's what the generated media is set to. Looking at the waveform monitor set to Studio RGB it shows levels that are illegal going from 109 to -8 which is what I'd anticipate if I printed that to tape as is"

Understood. And if 16-235 material is on the timeline it maps to 0-255 on the waveform with the Studio RGB switch "on," which is also to be expected.

But I'm kind of a lazy slug anyway, and use the histogram for most of my leveling. Histogram does not use that switch, and rereading the Help file tells me it is there to emulate PTT levels on the waveform, the way you are using it. These days maybe more useful to visualize YUV playback levels on flash-based and the majority of PC players. . .