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class="Paragraph" style="margin-bottom: 0">AG - DVX100 Black Levels

Published : 26th January 2004

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I know we've covered black level here before, but now I'm really confused. The JVC website claims that some* prosumer DV cameras can record a non-standard black level, if you have the setup properly switched for MONITORING at 7.5 setup.

What this says to me, is that I am not monitoring an image with the correct black level, as I shoot DV at zero setup. WTF, perhaps I misinterpret.

So I'm asking a favor: Could someone with gear run the following test?

There is a 5 minute flash tutorial about black level setup on the JVC website. It's largely about dubbing procedures, but if you can get through that, the last minute or two deals with cameras. It suggests changing the setup switch while viewing a monitor which is attached to the camera via a digital deck.

I'd love to know what cameras this affects, or if the claim if phooey.

Please go to :

class="Paragraph">http://pro.jvc.com/prof/main.jsp

class="Paragraph" and click on the black level setup tutorial.

Thanks!

Chris (I want to only shoot film now) Mosio
Cinematographer/Seattle



First of all, that's a great tutorial! I'm still confused, but at least now I'm more educationally confused.

I ran my DVX-100 through the test and it appears that it "suffers" from changing the black level output to the camera as well as to the monitor. But here's where I'm confused.

Is JVC saying that because all monitoring devices are analog, that the camera should output black levels at 7.5 setup regardless of how the camera is set up (small pun
intended)? So if the camera is set up for 0 IRE, the output would add setup to 7.5 IRE to be compatible with analog monitoring (otherwise the blacks would be...crushed? No, milky...wait...???) and if the camera was set up for 7.5 IRE, it would do nothing?

And if you set your camera to record 7.5 setup, then you're shooting non-standard milky blacks?

Dan Coplan
Cinematographer/Editor/DVD Authoring
www.dancoplan.com



>What this says to me, is that I am not monitoring an image with the correct black level, as I shoot DV at zero setup.

The JVC animation is factually correct on the tech (if you ignore the puppy pix, which have contrast as well as black level variations), but is hysterical in tone and offers an unworkable workflow.

Instead of flipping the "setup" on and off, simply set your monitor to 0 IRE setup instead of 7.5 IRE setup (which you can do using the camera's built-in colorbars if it's a half-decent camera) and leave the menu setting at zero. In that way, blacks will be shown as blacks. No problem.

But of course, you already *always* calibrate your monitor on-set anyway, right?

The Sony DSR-PD150 and Panasonic AG-DVX100 both have "setup" settings that bugger the digital data. The DSR-500 has a *proper* add-setup-on-analog-output setting.

More at :


http://www.adamwilt.com/DV-FAQ-tech.html#Setup

Cheers,

Adam Wilt
Menlo Park CA USA



I shoot stuff on DV. I Firewire into FCP. I output to DV, DVD, and VHS. I understand that going to DV and DVD, everything is cool. What about going to VHS? Do I need to add setup for that and if so, what's the best way?

My setup is very simple: FCP > DV camcorder (used as a deck) > higher end consumer grade S-VHS VCR (which I doubt, very much, has a setup switch).

If I do need to make a setup adjustment, this implies I can't master to DV and VHS at the same time unless I get an additional piece of hardware to do the setup adjustment between my DV deck and VCR, right?

I've read a number of articles on this whole setup issue including Adam Wilt's which really, just confused me more (not a knock on Adam - his site is like a bible to me, but his level of info processing is far beyond my limited capacity).

Dan Coplan
Cinematographer/Editor/DVD Authoring



>I shoot stuff on DV. I Firewire into FCP. I output to DV, DVD, and VHS. I understand that going to DV and DVD, everything is cool. What about going to VHS?

Run your DV camcorder's S-Video output into a proc amp and use it to add setup (and probably desaturate chroma a bit, too, if going to VHS), and use the proc amp's S-Video output to feed your S-VHS deck.

Adam Wilt
Menlo Park CA USA



>My setup is very simple: FCP > DV camcorder (used as a deck) higher end consumer grade S-VHS VCR

Your DV camcorder has analog out so you can connect directly to your VCR and do both transfers at the same time.

Robert Rouveroy csc
The Hague, Holland



>simply set your monitor to 0 IRE setup instead of 7.5 IRE setup (which you can do using the camera's built-in colorbars if it's a half-decent camera) and leave the menu setting at zero.

Yeah, I follow, which is in theory what we've all been doing. But this assumes (I think) that the setup switch affects the setup of the bars as well. Since no one has complained of crushed blacks, I must assume this switch also changes black level on bars. Or am I still confused?

Chris (I got the white levels all figured out) Mosio
Cinematographer/Seattle



Dan Coplan writes:

>I've read a number of articles on this whole setup issue including Adam Wilt's which really, just confused me more (not a knock on Adam - his site is like a bible to me, but his level of info processing is far beyond my limited capacity)...

Adam gave an excellent talk on just this subject tonight at SF Cutters. The bottom-line rule of thumb, as I understand it, is fairly simple :

- When shooting digital video, leave your setup at zero.

- When dubbing from digital to VHS, don't worry about the setup level.

- When dubbing from digital video to any analog tape format **for NTSC broadcast in the Western Hemisphere**, check your analog signal with a calibrated waveform monitor and if your DV player's *analog* output has not automatically raised your setup to 7.5 IRE, then use a standalone hardware proc amp to raise it to 7.5. If a proc amp is unavailable, make a temporary digital version of your program that has its setup raised to 7.5. After dubbing it to analog, trash the temporary version to avoid any future mixups.

Did I get it right, Mr. Wilt?

Dan Drasin
Producer/DP
Marin County, CA



All this time, I've been color correcting my videos against the output to my analog monitor without referencing the monitor on my deck (camcorder). This suggests that my black levels are OK when I output to VHS, but are washed out when I dub to DV? I never considered comparing the two (never thought I had to!).

"You Live And You Learn...And You Learn...And You Learn..."

Dan Coplan
Cinematographer/Editor/DVD Authoring



>Your DV camcorder has analog out so you can connect directly to your VCR and do both transfers at the same time.

That's what I've been doing, but it sounds like I need to go through a proc amp to add setup to the analog out in order to do both transfers at once. Otherwise, my DV transfer is fine, but my analog transfer has crushed blacks.

Dan Coplan
Cinematographer/Editor/DVD Authoring



I feel like a first-grader with a short attention span trying to figure this s**t out.

>When dubbing from digital to VHS, don't worry about the setup level.


Doesn't this conflict with your following statement where you indicate going to any analog tape format (VHS is one) requires adding setup through a proc amp? Or is the idea that if it's not for broadcast it's not worth the trouble?

"An MFA Graduate With a Short Attention Span"

Dan Coplan
Cinematographer/Editor/DVD Authoring



>simply set your monitor to 0 IRE setup...this assumes (I think) that the setup switch affects the setup of the bars as well.

Ooh, good question!

On my PD150, the setup control has NO effect on bars: the black bar is ALWAYS at 0% / 0 IRE.

On my DVX100, setup affects bars.

I'll update my website to reflect that, thanks.

Cheers,

Adam Wilt
Menlo Park CA USA



>When dubbing from digital to VHS, don't worry about the setup level.

Erm, not really. For RELEASE copies, yes, you should add setup to VHS copies. But for home movies, quickie work tapes, and the like, it's not as critical, and you can get away without adding setup because (a) these aren't quality-oriented applications, (b) most consumer sets are so misadjusted that it's anyone's guess where their black levels are,

Every consumer-level Video8, Hi8, and VHS camcorder I've ever put on a 'scope fails to add setup, but their picture levels were so all over the place and so, err, "challenging" to use in multigeneration work anyway that no one ever noticed. 7.5 IRE setup maintenance was the *least* of the color-under crowd's problems.

Adam Wilt
Menlo Park CA USA



> Since [DV] audio is on the outside edge of the tape...

The audio sectors are on the lower ends of each slant track, just above the ITI sectors. Check out : Figures 3 & 4 at


http://www.chumpchange.com/parkplace/Video/DVPapers/dv_formt.htm

S o yes, it's possible to get transport misalignment such that audio get glitched a lot more than video.

Only DVCPRO adds a control track (really LTC) and a linear audio cue track (the optional tracks 1 & 2 in figure 3). Both of these are used only for stunt-mode playback; the control track allows the tape to be unloaded from the scanner for really fast shuttling without losing track of position, while the linear cue track allows Mickey Mouse (tm) audio during jog and shuttle ops. In normal playback auto-track-finding is used for tape positioning and the embedded PCM audio is used for audio, just as in DV and DVCAM.

Adam Wilt
Menlo Park CA USA



Dan Coplan wrote:

>What about going to VHS? Do I need to add setup for that


Yes.

>If I do need to make a setup adjustment, this implies I can't master to DV and VHS at the same time unless I get an additional piece of hardware to do the setup adjustment between my DV deck and VCR, right?

Yes.

The "correct" method would be a proc amp between the analog output of the DV camera and the analog input of the VHS machine. A low-cost consumer-level proc amp like the Sima model SSC (under a couple hundred bucks) should be adequate for making VHS dubs.

The seductive, yet dangerous, alternative is to add "fake" setup digitally through a "broadcast safe" filter in FCP. Then you can master simultaneously to DV and VHS, but you MUST then understand the following …

A) You've added a layer of rendering to your DV master, which can significantly degrade DV footage, defeating one of its prime attractions (that edited material is essentially a clone of the original)

B) Your DV master is WRONG. Your footage no longer conforms to digital video black level standards (setup is an NTSC analog-only standard). If you, or someone else, uses the finished footage in the future, you will run the risk that it will not match black levels with properly-recorded DV footage. In addition, if it ends up going through a broadcast filter again in FCP, its black levels will be raised again...

I'm not saying you should never make a master in that way. There could be some legitimate reasons to do so in a particular case. But it is a very tricky proposition.

Incidentally, the same issue applies captured in a DV system from material dubbed from an analog source...if it was dubbed to DV from Beta SP, for instance, was the analog setup removed? (IT SHOULD BE, but often isn't).

If, as is the case where I work, Beta material is routed through a DV deck and captured directly into a DV-based NLE, then there should be a proc amp to REMOVE setup when digitising.

The correct workflow is that ALL (NTSC) ANALOG material should be recorded with setup, and NO DV footage should have setup (whether imported from Beta, or DV camera original, or finished DV masters.) Proc amps should be inserted in your dub chain where necessary, and dub houses should be reminded of your requirements, to meet this standard.

That's the gist of what Adam is getting at on his site.

Then there is the whole can of worms having to do with color bars...I believe that color bars are commonly miss-used in the DV world and do more harm than good, for a number of reasons, including this black level issue.

Best,
Mark Schlicher
Writer/Producer/Camera
Point 3 Nashville



>The "correct" method would be a proc amp between the analog output of the DV camera and the analog input of the VHS machine.

If I sent my DV tape master to a dub house like Lightning Dubs, would they add the set-up for VHS dubs? Would you have to tell them?

David Mullen
Cinematographer / L.A.



>If I sent my DV tape master to a dub house like Lightning Dubs, would they .add the set-up for VHS dubs? Would you have to tell them?

David,

I don't know if you directed this question at me, but my answer is :

1. If you have color bars at the head of your DV tape, the dub house should line up your dub to bars. Make sure your bars are correct. I was messing with FCP today and it appears that they generate the appropriate bars, which I believe should be the SMPTE bars with the "super black" -- the leftmost bar of the black "pluge" bars-- at the same black level as the middle pluge bar. This is the area that should be raised up to 7.5 units of setup.

2. They "should" add the setup for the VHS dubs. Whether they would, I don't know.

3. If it were me, I would tell them.

Best,
Mark Schlicher
Writer/Producer/Camera
Point 3 Nashville