I'm all perplexed: video scopes

[Josh Bass]

And one more thing, when calibrating the monitor on the shoot, I should add the in-monitor 7.5 IRE bias before setting it up according to the bars (from the XL1s, SEMPTE bars with no bias, as you said), or after?

And if you don't know about the web question, is the setup confusion issue a reason it might look dark on another TV, or projection screen?

[Bill Ravens]

1-before
2-setup level problems don't manifest themselves as pictures that are too dark. The only symptoms I'm familiar with are 1-the blacks being too light or washed out, muddy or 2-excessive color banding in the image.

[Bill Ravens]

hey Josh...

check this out....

http://pro.jvc.com/pro/attributes/pr...p/JVC_DEMO.swf


it makes it a lot clearer to understand.

[Josh Bass]

Holy crap dude. . .now I'm so confused I think I'm gonna cry. I will never shoot anything again.

Here's another NLE question:

The video scope, in addition to its "add 7.5 IRE setup option", also has a choice to select "Studio RGB 16-235". Now, do I want that checked if I'm not using a proc amp or anything? The tutorial mentioned black was ALWAYS recorded at 16 from DV cameras, but I'm still confused.

I can add setup in camera, to a certain degree. On the tutorial, the guy said that when changing setup levels, if you can see the level change on a monitor as you adjust it, that means that you have a camera that changes both the analog and the digital setup levels, instead of just the analog, right? Well I do, apparently. And tutorial guy also says if this is the case, then you have to add the 7.5 when lighting, but take it away to shoot, and add it again every time you relight?

[Bill Ravens]

first...ignore the part about changing when lighting...that was an example that confused me, too. he was talking about what was wrong to do, anyway.

The confusing thing for you, I suppose, may be that IRE and RGB are two different ways of measuring the color mapping. All DV cams map to RGB which is 0-255, BUT, to give DV some headroom, colors are mapped to 16-235 instead of the full range. SOooo, 16 corresponds to pure black and 235 corresponds to pure white. Now, if I speak of this in IRE terms, then I say 100 IRE is pure white, or 235 in RGB. Now the black or setup level is a little more complicated, yes? In IRE, black is 0 or 7.5 depending on the whether it's digital or analog. Both are RGB 16 if the setup level is set right. If it isn't set right, it can be higher or lower, depending on where the setup was fubared.

Confused yet?

[Josh Bass]

Yes. . .so, in my NLE, do I want to assume that everything was correctly setup and leave that box I mentioned above checked? Also, I'm thinking, if I use that switch in my NTSC monitor, the one that lets you add 7.5 IRE setup, and light and shoot to that, that shoot make me safe for NTSC broadcast sources, no? In other words, if I light referring to that, and I don't have any areas in my picture that are totally lost and black, then I should be okay for analogue sources, right?

And what if I just pump up all the blacks/dark areas in post (using color curves or somesuch), till the darkest dark reads 7.5 or above, according to the NLE software waveform monitor WITHOUT the "7.5 IRE setup" box checked. . .is that the same difference?

I just don't wanna be like the guy on the tutorial whose puppy pictures either looked too washed out or too dark, and I'm still not sure how to get there.

[Aaron Koolen]

Ok, I'm going to try and get things clarified myself as this still confuses me to a bit.

This is what I understand.

1) You can forget about setup until you are going to, or coming from an analog source. For this situation Josh is only talking about output anyway.

2) Josh needs to find out if his camera adds setup when it does the D->A conversion for output to his monitor. If it does, then he can set his monitor to 0 IRE. If it doesn't then he'll need to set it to 7.5 to add the setup itself. That way he can see what it would look like in broadcast.

3) When he output's his final project, depending on how it's done he *may* need to add setup. If he's outputting from comp->camera->VHS then he needs to know if his camera adds setup (as above) and if it does, he's ok, if not he needs to do the broadcast colours thing - right? If he's saying writing a DVD then he has no choice but to do Broadcast colours to make sure it's NTSC happy.

Is this right?

I'm in PAL land so I'm happy but I'd like to understand all this guff anyway.

Aaron

[Josh Bass]

Yes, I second what Aaron said, even though I hadn't thought about half that stuff. . .at least not in those terms. All I want is for my stuff not to look like crap, whether it be airing on a real TV station, or a digital projector.

[Bill Ravens]

The only REAL test, short of using a waveform monitor, is to create a test clip, maybe using a black and white 10 step ramp, then play it on a different system. Unfortunatley, testing it on your own system won't work because the error is self compensating within a single system.

Good luck. Oh, and you're right Aaron, you don't want to add setup twice...like once on the video card output and once in the monitor. Most monitors don't have that 7.5 setup switch. I 've read that if your video card or output signal isn't specified as one or the other, it's likely to be 0 IRE.

[Josh Bass]

Okay, were I using an external waveform monitor, during production, would I want to be safe and keep all video levels above 7.5 IRE? Or let the camcorder (or me) do what it (or I) want (s)? Add setup if necessary? This is keeping in mind that I don't have definite plans for final output, except that it'd mostly likely be NTSC.

[Bill Ravens]

Yes, by all means, keep it above 7.5 IRE. Many production studios will not accept an NTSC tape that exceeds legal standards. One note in Vegas4, there is a slider called "smoothness". Use this slider to blend the remapped blacks in a gradient rather than a step to avoid banding. I don't know how other pieces of equipment do the remapping.

[Josh Bass]

Sorry, confused again: if I do this during production, that is, while shooting--raising black levels and lighting so as to be above 7.5 IRE, I still need to remap in post with the broadcast colors filter?

[Bill Ravens]

Sorry to have confused you....I misunderstood your last question. No, if you raise the levels during production, obviously, there's no need to raise them in post. I would advise you not to raise the levels in production, however. Doing this in production means you're throwing away image information. From that point forward, you're constrained by that choice. If you capture the full range that the camera is able to capture, you always have the original tape to use, your options remain better.

[Josh Bass]

Okay. . .so you recommend what, then? Should I set my monitor only to the 7.5 IRE? So that I have to light. . .uh. . .brighter to get the same result as I would with 0 IRE? Or should I leave everything (monitor, camera) at 0 (though I've recently discovered I like the look of the pedestal lowered two notches from the default setting on the XL1s) and do all the screwing around in post?

[Rob Lohman]

Keep in mind that DVD players should auto conform the signal.
So you can burn a DVD with a 0 IRE floor and just leave it at
that (some testing might be in order to confirm this).

If you want multiple output options then I would shoot at 0 IRE.
If output is always NTSC broadcast or you know that for a
particular shoot set the camera up to start at 7.5 IRE and lower
the zebra stripes to something like 90% as well.

Last time I did a 7.5 IRE floor change in Vegas I could definitely
see the changes in the picture. It was almost like a shine through
curtain was put up. Contrast was dropping like a brick.