more studioRGB questions

kairosmatt wrote on 4/1/2009, 5:55 AM
Hi all,
There is a very good thread going about this, but I had some specific confusions I wanted to clear up.

1. If I calibrated an external monitor (JVC TM-H150c via S-video) with the color bars in Vegas, I think then it is calibrated to computerRGB. Is this true?

2. If true, if I put the computerRGB-StudioRGB filter on the bars could I calibrate the montior to studioRGB?

3. It seems that when I render to DVD everything looks great, but when broadcasted it is clearly not right. Does this mean that Vegas is converting the levels when rendering to MPEG2 or that DVD players are able to convert computerRGB themselves?

Thanks for any help clearing this up!
kairosmatt

Comments

rs170a wrote on 4/1/2009, 6:14 AM
1. Colour bars are already Studio RGB (16-235), not Computer RGB (0-255).

2. See #1.

3. What do you mean by "clearly not right"?

Mike
kairosmatt wrote on 4/1/2009, 6:19 AM
Thanks Mike,
What I mean by clearly not right is that you can't see the features on the faces of my host (he's black) and the highlights are blown out.
It could be something to do with how the cable company handles stuff (they aren't really on top of everything technical) but I know that if I convert everything to studioRGB before sending it things look better.

kairosmatt
Robert W wrote on 4/1/2009, 6:54 AM
I think there is some confusion here. You would not calibrate a monitor to Studio RGB or Computer RGB. These are theoretically just ways of storing colours digitally. If rendered correctly they should look similar (but not the same) on screen.

You could calibrate to an actual colourspace, such as a sRGB standard, or Adobe RGB, or whatever the rest of them are called, but Studio RGB and Computer RGB are completely different things.
kairosmatt wrote on 4/1/2009, 7:19 AM
Okay, looking at what Robert said and re-reading Glenn's stuff I am getting closer to understanding. Its just different units...but I'm still not 100% certain of everything.

I shot video, its measured in studioRGB. When I come to edit, my displays are in computerRGB. When I go to output, I need studioRGB (unless its for the computer display).

So my display won't be exactly correct as I try CC?

Another things is that some video I shot (on HDV) has values on the Vegas histogram more than 235 and less than 16. Is that the overhead built into the camera? If I understand it correctly: those values under/over can be saved with levels, but if untouched when broadcasted they would be lost?

thanks for everyone's patience!
Robert W wrote on 4/1/2009, 7:34 AM
Working in Studio RGB and Computer RGB depends on the codec and what it expects to "see". In Studio RGB the values below 16 and above 235 provide headroom. So if you darken as Studio RGB image in post, there will be data that is out of the normally visible range brought into view. With Computer RGB you would get hard and possibly visible 'clips' (solid demarcations of colour at the darkest points) as it runs out of data.

HDV is generally Studio RGB. Vegas displays all video by default in Computer RGB. That means it will display the data in the headroom range on screen, and squash up all the colours inbetween to make room. Hence the whites are dimmer and the darks are lighter, and everything looks a bit washed out. There is a way to change that from within Vegas, but it is a bit erratic. So upon advice from people here, if I want to work in the correct colours, I use a colour corrector plugin on the track, using the Studio RGB to Computer RGB.

As MPEG 2 is a Studio RGB format, it is important to remember to disable the Studio RGB to Computer RGB conversion before rendering.

If you are rendering to a Computer RGB format like WMV, then you need to make sure all Studio RGB files have Studio RGB to Computer RGB conversions in place prior to rendering.

Please note: As a few people on here will tell you, Studio/Computer RGB mode handling is broken in Vegas's 32bit video mode, so my best recommendation would to be to stick to 8bit mode for the time being.

I hope this is of help.
kairosmatt wrote on 4/1/2009, 7:50 AM
Robert: "I hope this is of help."

Very much so! Thank you.

Just one more question: When Vegas displays HDV (or other formats) in computerRGB is there any actual information lost when the middle colors are squashed up?

kairosmatt
richard-courtney wrote on 4/1/2009, 7:55 AM
While not technical answers to studioRGB thought I'd chime in on seeing
facial features on dark skinned talent.

This creates some issues while recording so additional lighting
techniques will help.

Adding some yellow to your key light will help warm the face. Normally, on light
skinned talent you powder, I have an assistant simply blot the perspiration.
A small amount of shine actually helps outline the features.
Obviously don't cook your talent with your lights just to get specular highlights!

LCD's are terrible in the way thry present near black level so you can, if
your cameras has the function, adjust the luminance curves.

Just some thoughts.
kairosmatt wrote on 4/1/2009, 8:01 AM
Thanks Courtney,
We have been using gold reflectors lately and the results are dramatically improved.

Often times though its just me one chasing our host around in the outdoors, so I was thinking about getting a small LCD, like the litepanels.. But its seems this might not be the right approach for us based on what you are saying. I can't adjust the luminance curves directly onmy camera, but I have several preset gamma curves I can play with. Any suggestions?

kairosmatt
Robert W wrote on 4/1/2009, 12:09 PM
"When Vegas displays HDV (or other formats) in computerRGB is there any actual information lost when the middle colors are squashed up?"

I might have the numbers wrong here, but this is rough how I understand what goes on. If you decode a Studio RGB image as Computer RGB things like this happen:

1) Pure Black in Computer RGB is R=0 G=0 B=0. Pure Black in Computer RGB is R=16 G=16 B=16.

2) If a decoder looks at a Pure Black in a Studio RGB image and thinks it is looking at a Computer RGB image, it displays the colour you would get with Computer RGB at R=16 G=16 B=16. That colour is a dark gray.

3) Pure White in Computer RGB is R=235 G=235 B=235. Pure White in Computer RGB is R=255 G=255 B=255.

4) If a decoder looks at a Pure White in a Studio RGB image and thinks it is looking at a Computer RGB image, it displays the colour you would get with Computer RGB at R=235 G=235 B=235. That colour is a light gray.

5) The result of this is a colour shift across the whole range of colours.

6) Also data in the headroom will be visible in the bright whites and dark grays.

In answer to your question, if you convert Studio RGB to Computer RGB, you will lose colour information in the headroom, as it should be clipped in the conversion. If you render to a Studio RGB format you should remove all Studio to Computer RGB conversions. Also, you should place the conversion at the end of the plugin list, after any colour curves to ensure you do not clip useful data which will come into play when you remove the conversions.

I hope this makes sense. I may have over complicated it a bit.
rs170a wrote on 4/1/2009, 12:24 PM
Don't overcomplicate things here.
All you need to do is to open up a new instance of Vegas, drop colour basrs on the timeline without adjusting or addding any FX to it and set your JVC accordingly.
I've got the exact same monitor in 4 student edit suites and that's how I set them up.
BTW, I feed colour bars from a broadcast-grade Leitch test signal generator to the B input of the JVC and my monitor display is identical to what's coming out of Vegas.

Mike
kairosmatt wrote on 4/1/2009, 1:39 PM
No, not overcomplicated, but starting to make sense. Is this right below?

Vegas is looking at StudioRGB and thinking its seeing computerRGB, hence it is washed out. And it makes sense, as suggested, to add a converter to the trackFX for reference and then turn it off when rendering. Because Vegas will just pass through the original video to the new codec without converting the colorspace (unless you add a filter to do this.)

Getting there....I hope!
kairosmatt
Robert W wrote on 4/1/2009, 2:19 PM
Yes, I believe that is spot on.

It does take a little while to get your head around. You also have to be very careful when using the presets because it is easy to place both a Studio RGB to Computer RGB and a Computer RGB to Studio RGB preset on the same timeline, and end up with a slow change between the two modes in your final video.
farss wrote on 4/1/2009, 2:52 PM
You said somewhere above that your camera is recording blacks below Y' =16, I've yet to see a video camera that does this and I've looked at a lot of video from a lot of cameras with the Vegas waveform scope. Are you certain you scopes are setup properly e.g. do you have the 7.5 IRE Setup box checked?


Black people on blackout cloth are a regular gig of mine.
If your camera has an adjustment called Black Stretch or Black Gamma this may help. Lighting as you've been advised and found out also helps.

Bob.
Yoyodyne wrote on 4/1/2009, 3:01 PM
Interesting discussion, I'm with Mike on this one.

You should be able to set your monitor to the color bars out of Vegas and have that be an accurate reference.

This is via "preview device OHCI Compliant IEEE 1394/DV" - correct?
kairosmatt wrote on 4/1/2009, 3:33 PM
You know what Bob-I think you're right. I don't see any values below 16, very few even near it really. But I definitely have values above 235.

I don't know if my scopes are set up correctly. The studioRGB box is checked, but I'm not sure why setup would be checked. I know that my camera can add setup, but everything I've read said that you shouldn't do that.

Yoyodyne, my preview device is off S-video cable from the graphics card. I calibrated it as Mike suggested above, so I think its right.

thanks
kairosmatt
Yoyodyne wrote on 4/1/2009, 3:52 PM
"preview device is off S-video cable from the graphics card."

Hmmmm, I have never been able to get any kind of reliable preview running this way.

I am no guru but I'm thinking either preview to firewire device or secondary monitor with "use studio RGB" selected (sRGB color space profile) is going to give you better results. Is it possible to do a test?



rs170a wrote on 4/1/2009, 4:07 PM
Hmmmm, I have never been able to get any kind of reliable preview running this way.

Yoyodyne, that's my thinking as well as reading in various Vegas forums.
My signal goes from the computer to a miniDV deck via firewire and then to the monitor.
A Canopus box or a camcorder with pass-through would work the same way.

kairosmatt, check out Glenn Chan's article called The 7.5 IRE Setup Problem.

Mike
GlennChan wrote on 4/1/2009, 7:30 PM
Yoyodyne, my preview device is off S-video cable from the graphics card.
For reasons unrelated to levels, I wouldn't do this. Preview through firewire to a camera or something like that. You'll see the proper handling of the non-square pixels, interlacing, overscan, etc.
(And use a SD CRT.)



No???

You're looking at it the wrong way I think.

What's happening to the signal is this:

RGB --> Codec / compressor --> Firewire (as Y'CbCr values) --> D to A converter --> monitor as an analog signal.

What you need to do is to send the type of RGB values that your codec expects. In this case, it would be the Sony Vegas DV codec (unless you mucked with the preferences; don't do that). The Vegas DV codec expects studio RGB levels. The color bars generator in Vegas is appropriate for studio RGB levels. So do nothing.

2- The D to A converter may not correctly convert from digital to analog. It may put black at 0 IRE when the standard in your country is 7.5 IRE. This is ok if you calibrate that away (calibrate color bars like you would normally).

Just be aware that your monitor would then be calibrated to your DV camera, and may/will not have the right calibration for other sources.

=======
Recap:
1- Don't do anything to the bars, just throw em on the timeline.
2- Calibrate your monitor. Done. That's it!!!
Ok ok, 3- Be aware that your monitor is not calibrated to other sources (e.g. DVD players... some put analog black level at 0 IRE, others at 7.5 IRE).
GlennChan wrote on 4/1/2009, 7:33 PM
BTW, I feed colour bars from a broadcast-grade Leitch test signal generator to the B input of the JVC and my monitor display is identical to what's coming out of Vegas.
Are you sure about this? I believe Vegas gets the I and Q bars wrong (the blue and purple bars in the lower left corner). But nobody use those, so it's ok.