601 or RGB when importing Avid color bars?

[Jon Zanone]

I use 601 for everything. There is a very good reason for this, and I researched it completely before making the switch.

Unfortunately, the buffer overwrite has kicked in and now all I can remember is something about eggs….

I recall the RGB bars came in hot on our scopes. Not screaming, but hot enough so that if someone set our video to bars, the video would be about 5-10 IRE to high. 601 seemed to come in at the correct levels.

Jon

“So you want to throw out the old you – but the old you is old enough to know it won’t make it better”
Del Amitri – “Make it Better”

[Bill Russell]

Well, thanks. Oh how confusing. There is no danger of “doubling up” — adding 601 to 601? Funny — when importing Avid’s own bars tif using 601 they scope internally (Avids software scope) too low, just the opposite of what you get externally. Do you get that too? I don’t have SDI out or any external scopes to compare.

Sigh — I’m accustomed to FCP world where levels (on video, but graphics another story) are just plain correct in and out or import to export. Somehow not having the RGB / 601 /709 video options is not a disadvantage in FCP.

– B

[Ra-ey Saleh]

The bars were created with ‘601’ levels – as they are video in origin – so need to be imported with ‘601’ levels.
You also want to select ‘Non-interlaced’ or else you’ll get a weird black line on the left of frame.

Ra-ey

[Bill Russell]

Makes sense, except… why do they scope too low in Avid’s internal waveform when brought in as 601?

[Jon Zanone]

Do you have “NTSC has setup” box checked in the (I think) general settings?

Jon

“So you want to throw out the old you – but the old you is old enough to know it won’t make it better”
Del Amitri – “Make it Better”

[Richie Morgan]

I am writing this response for the original poster as much as for myself to help get this straight in my head, so please bear with me.
I consider myself a very novice user, but a quick search on google brought up a nice FAQ about this… https://xdvfaq.tripod.com/#4.12. I found it to be very descriptive. For the click impaired here is my take:
There are 2 types of color
You have Video color and Computer color:
Video color White to Black is 16-235 (601)
Computer color White to Black is 0-255 (RGB)
When you import with Avid you tell it what your source is by selecting 601 or RBG.
If you specify the source as RGB it will push the Whites and Blacks together to fit into the 16-235 range for video use
If you specify the source as 601 it will leave your colors alone (because it expects them to be already in the 16-235 range).

That’s my take, but read the linked material and compare.
If I understand it correctly,
Bars already in the 601 colorspace should be imported 601 to avoid Avid “Crushing” the colors
Bars in the RGB (standard graphics editing output) colorspace should be imported RGB so Avid can put the 0 whites and 255 blacks into the 16-235 range.
Does that sound right?

[Chaz Shukat]

Video color White to Black is 16-235 (601)
Computer color White to Black is 0-255 (RGB)

I think you’ve got this backwards. Video is RGB (16-235) and computer is 601 (0-255). So if you are importing a 601 computer graphic, you want to select RGB to have the file adjusted for video. If it’s already in an RGB color space of 16-235, select 601 so that Avid won’t adjust it further. However, for a matt, you want to leave that in 601 space so select 601 when importing so that it is not adjusted to RGB space, or else you won’t get a clean key.

Chaz Shukat
Author of “EDITING REALITY”
http://www.chazmoedit.com

[Robert Combs]

Can anyone else confirm or deny which of the last two posts in this thread are correct? They both sound possible so I’m now even more confused. Thanks. Rob

thanks

[Richie Morgan]

After doing a bit more reading, In essence we are both right, I just got my labels off.
The essence is:
-When you import as RGB it will push the Whites and Blacks together to fit into the 16-235 range for video use.
-When you import as 601 it will leave your colors alone.

Chaz is correct in that RBG = Video Colorspace and 601 = Computer Graphic Colorspace. The matte comment is one worth paying attention to, as well. Always import your mattes with 601.

[Bill Russell]

Thanks guys!!!

“Video is RGB (16-235) and computer is 601 (0-255)”

Must actually mean:
VIDEO = a subset of RGB
COMPUTER = 36 more bits than VIDEO

Is that right? I think so. Here’s why. Certainly in the graphics world, when you are working in 8-bit RGB (or CMYK, or Grayscale) you have 0-255. Period. True white is 255, true black is 0, and you have a full 256 extent per channel to work with. (16 bit gives you a whopping 65,536. 10-bit RGB image, for that matter, would be 1024.) Just open any graphics program (like Photoshop) and look at the levels you can work with per RGB channel. Graphics world does not know of any “601” where dark gray (16) is black and light gray (235) is white.

When creating titles in the 8-bit RGB graphics world to give to the video world (like when working in After Effects), I make whites slightly “gray” — darken them to about 229 or so — so they do not go over 100 IRE in the video world — I often shoot all the way down for close to 90 IRE. So it seems video world recognizes my 0 black, and (ah ha! I get it now) also recognizes my 255 white — it just puts that 255 white at IRE superwhite (above IRE 100). I think I get it — the video world is squeezing my black and white into video’s more limited 16-235 extent, video’s full black to SUPERwhite spectrum (0 to 105 / 110 IRE, whatever the digital above legal max is).

If I told Avid to import my graphic as 601, it would clip off the first 16 levels of my black and the last 20 levels of my whites? Just chops ’em off, throws ’em away from each end, that detail gone forever. But it keeps the middle level detail intact, one for one. Thus 601 is some weird 220 digital level space carved out of RGB. So in order to not lose end-to-end detail (but instead evenly diffuse the detail loss in downconversion from 256 steps to 220) I tell Avid to import as RGB, which causes it to squish 0 to 16, and 255 to 235 such that my RGB video “safe” of 229 white becomes, oh, something like level 208 of 601’s extent inside Avid.

The video world uses fewer steps between black and white than RGB. Thus Avid will scrunch an RGB image to within 16 to 235 (235 being well above 100 IRE).

So, the labels quoted at top confuse me, but Chaz and you are on in the description of the results. Video seems to throw out 36 bits from the “ends”. Here’s a description:
https://www.digitalvoodoo.net/products/10bit/

> -When you import as RGB it will push the Whites and Blacks together to fit into the 16-235 range for video use.
> -When you import as 601 it will leave your colors alone.

I get it. This is from Video’s perspective.

Not because Computer is 601, but rather, VIDEO is 601, right?

So then, when EXPORTING video to a DV stream, or to an uncompressed movie, whatever, where color bars would be correct in a straight video import to any system (like FCP, which doesn’t offer a 601 / RGB distinction) — one should use 601 or RGB? In other words, how to export video so that the exported DV (or uncompressed or whatever) is identical to the very original DV (or uncompressed) stream before it went in? Like say, I capture color bars from a DV tape, then I want to export back to a file as a DV stream or DV Quicktime movie. Which is “unfiltered” / “undistorted” export — 601 or RGB? (I mean, I could test this if I had a deck!)

What does Avid do with each of these options on export? My brain hurts.