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black levels and the pd 150


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#1 Bob Hayes

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Posted 11 July 2005 - 10:17 AM

Where do you PD 150 users set your black levels? Factory setting is 0 ire but it also has a 7 ire setting.

Edited by bob1dp, 11 July 2005 - 10:18 AM.

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#2 Peter J DeCrescenzo

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Posted 11 July 2005 - 11:14 AM

Where do you PD 150 users set your black levels?  Factory setting is 0 ire but it also has a 7 ire setting.

<{POST_SNAPBACK}>

My understanding is that for an all-digital post path (for example, capturing via Firewire and editing in an NLE), you keep a DV cam's Setup setting at "0" (zero) IRE.

For example, a 7.5 IRE setup value would be used in a multi-camera shoot if any of the cams were connected to an analog switcher via composite or S video. But if all the cam connections to the switcher are via Firewire, then 0 setup is used.

Adam Wilt discusses this topic on his website:
http://adamwilt.com/...tech.html#Setup

All the best,

- Peter DeCrescenzo
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#3 drew_town

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Posted 11 July 2005 - 12:14 PM

I shoot at 0. It's really just a preference. You can see a little more detail in the shadows with 7 but normally you'd just crush it back down in post. So for me it saves a step.
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#4 Peter J DeCrescenzo

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Posted 11 July 2005 - 12:35 PM

I shoot at 0. It's really just a preference. You can see a little more detail in the shadows with 7 but normally you'd just crush it back down in post. So for me it saves a step.

<{POST_SNAPBACK}>


Hi Drew: I may be mistaken, but I thought you actually "lose" (as in gone for good) some dynamic range on "low end" DV camcorders if you use 7.5 IRE Setup and (for example) capture via Firewire and edit in a computer NLE.

Again, I may have this wrong, but that's my understanding of what Adam Wilt & others have described.

Can you (or maybe Phil R.) clarify this?

All the best,

- Peter DeCrescenzo
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#5 drew_town

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Posted 11 July 2005 - 04:10 PM

So you're talking about how you would set it up if you were using S-vid (analog) out? I really don't know about that one. I've never used a digital camera's analog comonents other than to monitor.
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#6 Jeremy Russell

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Posted 11 July 2005 - 04:27 PM

I don't think it matters in what situation you are shooting. Be it multi camera or single camera, switcher or no switcher, s-video or anything else.

NTSC standards are setup for black level to be a 7.5 IRE. 0 is designated as "super black".
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#7 Bob Hayes

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Posted 11 July 2005 - 04:34 PM

I felt that when I shot the PD 150 with blacks set at 0 they looked really crushed. And with blacks set at 7.7 they looked great.
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#8 Peter J DeCrescenzo

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Posted 11 July 2005 - 05:04 PM

Hi everyone.

In Adam Wilt's article at the URL noted in my previous post, he says in part:

==============
"... Some DV and DVCAM camcorders like the AG-DVX100, DSR-PD150, DSR-250 can record a video signal with "7.5% setup." Is that OK?

The AG-DVX100, PD150 and DSR-250 have a "7.5% setup" setting in the menu. Don't use it! It does not add setup to the analog outputs; it modifies the digital data coming from the camera head by boosting the black level, resulting in washed-out blacks, reduced precision, and nonstandard tapes as described above. As a result the analog video played back from the camcorder or viewed live has its blacks at 7.5 IRE, so the signal looks like it has setup, but what it really has is a too-high black level!

The "7.5% setup" setting in these cams are really only useful if you're:

* using the camcorder as a camera only, in switched multicam shoots where the other cameras have setup;
* intercutting camera footage with off-air signals recorded on a deck like the DHR-1000 that similarly does not remove setup on analog inputs, thereby creating washed-out-black footage;
* intercutting camera footage in an NLE with images brought in via analog dubs to DV tapes or live E-E digitizing when such A/D is done using low-end decks/camcorders that do not properly remove setup from incoming analog signals.

In these last two cases be aware that you're essentially working in your own little nonstandard "island" of washed-out-black digital data, and that intercutting with properly-digitized material won't be possible without (a) black level shifts or (B) lots of annoying rendering using the levels filter.

Do not confuse these cheap imitation "7.5% setup" controls with the genuine, pukka article as present on DSR-300s and 500s and the like. Those "add setup" controls in "Real" cameras are proper analog setup tweakers that do not screw up the digital data. ..."
============

(Refer to the link above for the rest of Mr. Wilt's article.)

The above is what leads me to believe that NTSC PD-150 (and many other) DV users should not typically adjust their camcorders to record with a 7.5 IRE "Setup" value. Instead, the "Setup" feature on these cams should typically be set at 0 (zero).

Also, you may have noticed a PD-150 doesn't feature built-in SMPTE color bars, the ones with PLUGE bars in the lower right corner. My understanding is that you should adjust/calibrate your production monitor by connecting it to the analog outputs of a camcorder like the PD-150 and play a tape in the cam which has SMPTE bars recorded onto it. Or, connect the monitor to the cam, and connect the cam's Firewire port to a computer running an NLE which outputs SMPTE bars. You can record these bars onto tape or the cam's memory stick for later use.

If my understanding concerning the above is incorrect, please advise.

All the best,

- Peter DeCrescenzo
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#9 Gordon Highland

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Posted 11 July 2005 - 05:13 PM

I felt that when I shot the PD 150 with blacks set at 0 they looked really crushed.  And with blacks set at 7.7 they looked great.

<{POST_SNAPBACK}>


Are you talking about in the viewfinder, on your field monitor, or in the computer?

Whether it's at 7.5 or 0, if your monitor is calibrated according to bars set up for having "setup" or for not having it, it should look the same by eye. When you capture that footage and cut it alongside Betacam footage (that always has 7.5), the DV blacks will look crushed assuming your monitor is set up for Betacam. If the monitor was set up for 0 DV stuff, the Betacam footage will have milky-looking blacks, and you'll want to use levels to crush it back down to match with the DV.

Also, the color viewfinder on the PD-150 is notoriously misleadingly bright, thus resulting in underexposure if you're not careful. I leave LCD brightness control all the way down, and still rely on the B&W most of the time. Another gotcha with that camera, the early models had problems with audio hiss when in MANUAL mode, but NOT with auto gain control. Weird.

In Japan, I hear 0 is the broadcast standard.
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#10 drew_town

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Posted 11 July 2005 - 07:09 PM

The PD-150 and 170 are the worst cameras I've ever used in terms of judging exposure without using a field monitor (which you can't propperly adjust w/o color bars). It really just takes some test shooting to see what's going on. The LCD is completely useless to me other than for framing. 0 setup might be a little crushed but I think 7.5 setup looks too pale and milky. There's a number of things that will decrease performance from that camera, but it's not like you're working with most stellar machine.
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#11 Phil Rhodes

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Posted 11 July 2005 - 07:50 PM

Hi,

I'm afraid this isn't something I regularly deal with, as in PAL world, black is zero. It's my understanding though that non-EIAJ NTSC should always be shot with setup. Otherwise, you risk the codec misinterpreting what's going on and your blacks getting suddenly crushed when rendering a transition or something. In actuality I'm pretty sure most codecs are too stupid to take this into account so you'll usually get away with it, but I'd prefer to do it right and make adjustments rather than do something that happens to look right and risk it suddenly blowing up on you later in the process.

Phil
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#12 Sam Wells

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Posted 12 July 2005 - 10:17 AM

NTSC standards are setup for black level to be a 7.5 IRE. 0 is designated as "super black".

<{POST_SNAPBACK}>


DV cameras are based on Japanese NTSC which uses 0 IRE black level.

-Sam
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