What is Preferred Video Scope Setting?

Rich Parry wrote on 4/21/2012, 8:07 PM

Question: Should either of the two boxes (7.5 IRE and Studio RGB) be checked in the Video Scope Settings dialog box given the workflow described below.

I am a passionate amateur videographer who wishes to do a reasonable job color grading. I am not a profession producing for Hollywood studios. My work is for friends and family and will never be broadcast. My videos are rendered to MPEG format and burned to DVD or rendered to 1080P .MP4 format and uploaded to Vimeo. For rendering I use Main Concept codecs.

The Vegas Pro manual says both boxes should be unchecked based on my codec.
http://vegaspro.helpmax.net/en/using-vegas-software/adding-closed-captioning/video-scope-settings/#

I am currently adjusting levels with both Video Scope options unchecked. As a general rule, I adjust blacks close to 0 or slightly higher and whites close to 100 or slightly lower.

My research on the web, books, manuals, and forums say either both should be unchecked or only Studio RGB checked. With Studio RGB selected, true black is really a very dark gray, and true white is a very light gray.

Comments and/or suggestions welcome, thanks in advance.
Rich

Comments

SuperG wrote on 4/21/2012, 8:36 PM

There should be no 7.5 IRE setup. You should be using studio rgb with your project's pixel format set to either 8-bit or 32-bit (video levels).

NickHope wrote on 4/22/2012, 2:08 AM

I uncheck "7.5 IRE Setup" and check "Studio RGB (16 to 235)" and then I know that, on the waveform, 0 is black and 100 is white when the video ends up on DVD or the web.

If you are grading blacks to 0 on the waveform and whites to 100, and you do not have "Studio RGB (16 to 235)" checked, then all your lowlight detail (<16) and highlight detail (>235) will get clipped to flat black or white in the final video (in the vast majority of delivery scenarios).

To combat the "very dark gray" or "very light gray" you can check "Use Studio RGB (16 to 235)" in your Preview Device Preferences (for example if you're previewing on a Windows secondary display). Then your regular Vegas preview window will still show black as dark gray and white as light gray, but the secondary monitor preview will show you the extra contrast with black and white.

If you only have the preview window to monitor on then you can apply a "Studio RGB to Computer RGB" levels fx preset to get a preview of the final video, but remember to take the fx off again before you render.

If you've already mistakenly done a lot of grading to full range 0-255 and don't want to redo it, you could slap a "Computer RGB to Studio RGB" fx preset on the event, track, or video bus to get it back to the "correct" range of 16-235.

Grazie wrote on 4/22/2012, 2:43 AM

Nick! Fab-simple tutorial. Thanks.

Grazie

GlennChan wrote on 4/22/2012, 3:52 AM

Things would be a lot easier if Vegas were to handle levels for you.

The way Vegas currently handles things is extremely unintuitive and can be misleading.

2- Nick Hope's advice will work in most situations. If you want correct results for all situations... the answer is more complicated.

The simple solution is to put in a feature request. Vegas could potentially handle all this stuff for you like the other NLEs on the market.

Grazie wrote on 4/22/2012, 3:55 AM

Ok, Glenn, how would you frame such a request? What would I ask for?

G

paul_w wrote on 4/22/2012, 5:48 AM

This may or may not be of interest. I had a similar problem working out what exactly Vegas does with Black Levels. thread here:
http://www.sonycreativesoftware.com/forums/ShowMessage.asp?Forum=4&MessageID=804272Can someone explain to me Black levels in a track[/link]

It is quite a mess in Vegas and should really be improved. Has been like this for years :(

Personally, i would follow Nicks advice. I use 16-235 scopes (7.5 IRE is only for composit video signals using the NTSC system, not digital files, so keep unticked).
And basically, if you keep all your media on the TL within these 0 - 100% limits (with 16-235 ticked) you will be legal and the result rendered file will be correct for DVD, web etc.. Its more complicated than that, but basically thats the way to go.

Paul.

GlennChan wrote on 4/22/2012, 1:35 PM

Here's one possible approach:

1- Give an option for vegas to:
a- convert everything to studio RGB. This should probably be the default.
b- convert everything to computer RGB. (Probably make this the default for 32-bit projects.)

2- Vegas should automatically handle levels conversions when rendering/outputting the final product.

3a- In the scopes, have a dotted line at 7.5 IRE if the 7.5 IRE checkbox is checked.
3b- Highlight illegal values in red.
3c- There are other deficiencies in the scopes but I don't see the point in trying to solve them. For the very very few people where this matters, you should get scopes with SDI in/out anyways. Software scopes are a bad idea if you are making broadcast masters.

4- You can take things one step further and have a project setting for what type of NTSC country you are in. (Vegas can even auto-detect based on IP address possibly.)
If you are in a NTSC country which has black level at 7.5 IRE, then the broadcast colors filter and the scopes should be setup taking that into account.
If you are in Japan, then you would want to use the other option.

robwood wrote on 5/6/2012, 12:56 AM

^ +1 ...what Glenn said!

TeetimeNC wrote on 7/9/2012, 4:48 PM

Nick, thanks very much for your mini tut for color grading. I'm doing exactly that on a project that will be delivered to NTSC DVD and have a followup question. I have my waveform monitor set as per your instructions with Studio RGB (16 to 235) checked. My cam (HMC150) shoots 0-255, and that is what I see on the histogram unless I apply the levels filter for Computer RGB to Studio RGB.

My Questions:
1. Should my histogram be showing 16-235?
2. Am I supposed to apply the Computer RGB to Studio RGB filter?

/jerry

GlennChan wrote on 7/9/2012, 5:03 PM

Your camera probably does not shoot 0-255? It records to the AVC HD format. In Vegas, AVC HD will correspond to 16-235 in an 8-bit project (in in a 32-bit project it depends on a project setting). Your camera probably shoots illegal values above white level so you'll have values in the range of 16-255. The values above 235 will be clipped if you don't apply any color correction and if you apply the proper levels conversion.

If you see value below 16, it may be due to sharpening, noise, or any borders in the image.

TeetimeNC wrote on 7/9/2012, 5:37 PM

Ok Glenn, two things were screwing up the histogram. First, I had the sony sharpen fx on the video bus, set to 0.0. This, as you suggested caused the black to go to 0. Untick it and the value goes to 16. Second, I still had some faint values above the 100 line on the waveform which accounts for the 255 values on the histogram.

Thanks for the quick response Glenn.

/jerry

NickHope wrote on 7/10/2012, 3:20 AM

Jerry, take a look at this project I set up which includes a colour curve you might use as a starting point to grade footage that was shot nominally 16-255.

Please also consider doing the levels test with your camera and adding the results to that thread.

farss wrote on 7/10/2012, 3:29 AM

Nick,
I use a similar curve however I add a node near the top so that the slope (gain) remains same for all but the highlights which then roll off a bit sharper than in your curve. All a matter of taste plus it depends on what your camera does. Many cameras today have "cine" curves and "auto knee", the latter means just what your highlights are doing depends on exposure.

Bob.