About television range

[C. Ryan stemple]

Hey Marco,

Your scopes look perfectly normal! The full range of a 10-bit video signal is in fact 0-1023, but for broadcast, SMPTE has set the legal standards at 64-940. I know you don’t come from a tv/tape/video background necessarily, but think of it in terms of IRE: On a 0-100 IRE scale, 64 is remapped to “0” IRE, and 940 is remapped to “100” in broadcast.

Does that make a whole lot of sense? Probably not on the surface, but trust me that it is a good thing (any overexposed signals that you do have will not be clipped off, and it helps going from RGB to YCbCr).

And most importantly, be reassured that your scopes look fine! Hope that helps!

—
Carl Ryan Stemple
Color | Editorial | Photography
digitalbarbershop.com

[Marco Amaral]

Thanks Carl.
everything is the way I imagine. No surprises!

So, I delivered the right signal,
but… (and there is always a but)
I don’t know the process that transfer this signal for Digibeta and HDcamSR,
How can I control that the “tape lab” will do the things right?

I image that they receive a lot of full range videos from people that finishes the workflow in FCP,
and I think they put the signal in legal values…
If they changes anything the picture will be “double legal” so… grey!

I really want to learn more about this workflows from digital to tape.

[C. Ryan stemple]

I’m personally not familiar with this concept of “double legal” that you’re speaking of, but I do know a bit about laying off to tape. However, in my experience, I’ve always done online lay-offs via Avid, not FCP. Though I’m relatively certain that the basic concepts are sound either way.

(Converting a digital sequence from a computer NLE to an analogue signal into tape form is all about signal flow and color space – specifically, interpreting an RGB color space in YCbCr space. This is key in laying off to Digibeta via component lay-off, as your video signal will flow into the tape deck and onto the tape via three cables – Luminance (Y), Blue-minus-Luminance (Cb), and Red-minus-Luminance (Cr). For an HD lay off, all of these signals flow through the same cable. There is LOADS more to digital-to-tape lay offs, but that’s the basic gist.)

As I had mentioned before, it’s key to think in terms of IRE, especially when you’re dealing with tape. Where as broadcast-safe black for 10-bit video is 64, broadcast-safe IRE for analogue video is 7.5, which is also established by SMPTE and corresponds to it’s digital video equivalent.

I guess what I’m trying to say in a round-about fashion is…I really wouldn’t worry too much about it. If you’ve graded within the broadcast-safe limits, then your project should in theory be fine whether it goes out through digital broadcast or to tape media.

If it’s still concerning you, talk it over with your lab – they’re generally very helpful and competent!

—
Carl Ryan Stemple
Color | Editorial | Photography
digitalbarbershop.com

[Marco Amaral]

Thanks Carl,

yep, I think I will talk with the lab.
this way I can sleep better 😉

thanks