Comments

John_Cline wrote on 10/28/2006, 1:44 PM
That's what the waveform monitor and vectorscope in Vegas are for.
vicmilt wrote on 10/28/2006, 1:57 PM
Use the "Broadcast Colors" filter in Vegas - it will keep your output honest.

Then if you are on an Analog tape (BetaSP) make sure your levels are between 7.5 and 100 IRE - this is where you use the waveform monitor.

v
dvideo wrote on 10/28/2006, 2:15 PM
can you explain this further?
what is IRE?
Jay-Hancock wrote on 10/28/2006, 5:16 PM
The levels filter is also a good one for this. The broadcast colors filter chops off any colors that go out of range. With a bit more effort, using the levels filter you can squeeze all the colors until everything is in compliance. Which one works better can depend on the situation. If you've only got a little bit of color out of bounds, or you don't care about detail in the parts that are out of bounds (like a light fixture in the picture, for example), the broadcast colors filter may be better for you. In contrast, (pun intended), if there is a lot of detail that you want to preserve in the highlights and shadows, you may want to use the levels filter.

Also the broadcast colors can be used at the end of the FX chain as a safeguard to make sure nothing went out of range.
farss wrote on 10/29/2006, 12:11 AM
I use CC, made up my own preset.
Problem is Sony cameras run from 0 to 110 (that's with the Vegas scopes at Studio RGB) , the BC FX will clip the highlights. Don't know about the Levels FX but whatever you do, do it while watching on the scopes. Make certain you're not crushing the blacks or whites.
And just so no one in NTSC land gets confused, there's no 7.5 setup in DV, that gets added if needed during the D->A conversion.

Bob.
DataMeister wrote on 10/29/2006, 1:48 AM
"there's no 7.5 setup in DV, that gets added if needed during the D->A conversion."

Does that mean that DV colors are equivalent to 0-235 on the PC?

SimonW wrote on 10/29/2006, 2:03 AM
Also, don't forget to account for overshoot. You really need to find out what the broadcasters specs are. For example most of the channels here in the UK recommend -1 to +103. You also need to check on their colour specs too.
farss wrote on 10/29/2006, 2:07 AM
They should be 16 to 235, from most cameras they seem to go from 16 to 255.
SimonW wrote on 10/29/2006, 7:58 AM
Broadcast cameras most often have their black level set to 20mv which is above 16 digital black (although this can be reduced to taste). Consumer cameras are often terrible. For example the V1 that I tried out had black levels that went waaaaaaaay below 16rgb and whites that went all the way to 255.
Coursedesign wrote on 10/29/2006, 9:26 AM
The IRE standard is not used outside the U.S., and technically not in the U.S. anymore either (although you wouldn't know it from hearing everybody talking about it daily).

PAL broadcast standards can exceed 100 as has been noted, and Japanese NTSC doesn't use 7.5 setup.

This analog tube circuit coddling is ridiculous though. It's 2006 fer Chriss' sake!! Less' move on!

You really should learn a bit more than what' can be in one post. How about reading a few books on the subject while asking for help with your first tapes?

SimonW wrote on 10/29/2006, 12:39 PM
LOL! Well, you guys in the US are the ones wanting to continue using BetaSP. ;-) The rest of us have moved on to digital 16:9.
GlennChan wrote on 10/29/2006, 12:39 PM
1- In Vegas, there are three/four different color spaces you have to worry about:

a- Composite NTSC. There are transmission limits on the composite NTSC signals you can broadcast... for the composite signal (composite of both luma and chroma), the legal range should be around -20 to 115 IRE.

The NTSC standard allows for up to 120 IRE. However, (according to Charles Poynton's textbook) old TV receivers have problems differentiating video signals that high from audio... so the video will start bleeding into the audio. 115 IRE is more pragmatic for these old sets.

Some broadcasters will set even lower limits than 115 IRE, so you'll have to get their technical specs. One reason why they may do this is if they dub footage onto analog formats... some of them cannot handle composite video with very high IRE values. They may also do this for other reasons.

b- Y'CbCr (component digital video)
Most digital video formats use Y'CbCr colorspace. The legal range for Y' (luma) is always 16-235 (for 8-bit formats; 10-bit is 4 times that).

c- studioR'G'B'
This is Vegas' default color space. Vegas' scopes only monitor the 8-bit RGB signal. Your footage is processed in RGB, converted to Y'CbCr, and then later converted to composite NTSC.

studio R'G'B' differs from computer R'G'B' in the ranges for legal video. Studio RGB uses the 16-235 range, while computer RGB uses the 0-255 range.

When converting from RGB to Y'CbCr, you should ensure that the proper conversion is being done. Vegas' default for DV is that:
DV gets decoded to studio RGB.
When encoding DV, the sony vegas DV encoder expects studio RGB colors. So everything should be in that color space.

Unfortunately, Vegas is a little silly in that pictures decode to computer RGB space (so you need to convert them into studio RGB typically). As well, most filters assume computer RGB space.

2- If you are making a DIGITAL master, then you need to:

a- Ensure that the digital levels are correct. The YCbCr luma should range from 16-235 (assuming 8-bit). With the Vegas defaults, this will happen if your RGB levels are from 16-235. You can check this by looking at the histogram.
Vegas' waveform monitor is more complicated and inaccurate if setup wrong.

b- When your digital video is converted to composite NTSC, you want the composite NTSC video to be legal. To do this in Vegas, apply the broadcast safe filter:

Luma min 7.5
Luma max 100.0

Chroma max 100.00

Composite min -20
Composite max 115.0 *This varies from broadcaster to broadcaster!

Check both 7.5 IRE setup and studio RGB.

3- The broadcast safe filter can degrade the colors of your video; check that it doesn't. Here's how:

-Have the video scopes in the "all" mode.
-Put the BC colors filter on the preview output FX level.
-Go through your video, and toggle the BC colors filter on/off.
-If you see the scopes change, then your video is being affected. If not, then your video was legal to begin with (and the BC colors filter does nothing).
-Look at image visually on a calibrated external monitor. If the colors look worse visually, then you want to manually go in and color correct the footage.

Because some cameras record illegal superwhite levels (which are sometimes useful), you can use the levels filter to extract additional highlight detail.
article/tutorial
*Note that in the article, I recommend that you setup the waveform monitor so that it's (A) useful and (B) does not show you what the analog video levels would be. (B) doesn't matter much, as the BC colors filter means that you will have legal levels.

-At 115 IRE, the BC colors filter won't really do all that much. The only thing you have to watch for is that images are being converted into studioRGB color space. At more conservative levels (i.e. 100 IRE), then the BC colors filter can aversely affect the footage. If the highlights look de-saturated, use the color corrector secondary and target saturated highlights. Bring their gain down until it starts looking right.

4- An explanation of the whole 7.5 IRE setup thing (which you don't need to worry about too much):
http://glennchan.info/articles/technical/setup/75IREsetup.html
That article should hopefully clarify any misconceptions about 7.5 IRE setup.