7.5 IRE Setting at DVinfo.net

Go Back   DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony HDV and DV Camera Systems > Sony VX2100 / PD170 / PDX10 Companion

Sony VX2100 / PD170 / PDX10 Companion
Topics also include Sony's TRV950, VX2000, PD150 & DSR250 family.


Reply
 
Thread Tools Search this Thread
Old November 24th, 2004, 08:56 AM   #1
Trustee
 
Join Date: Jun 2003
Location: Somewhere in the Negev
Posts: 1,189
7.5 IRE Setting

My PD 170 has a 7.5 ire setting. When I select 7.5 ire in my menu, does this mean that my B & W viewfinder is automatically set to properly expose (through manual settings, of course) what I tape.

In others words, at the 7.5 ire setting, can I light accurately using my viewfinder as if I had proerly calibrated the viewfinder to the pluge bars?
__________________
Interesting, if true. And interesting anyway.
Hugh DiMauro is offline   Reply With Quote
Old November 24th, 2004, 09:51 AM   #2
Wrangler
 
Join Date: May 2002
Location: Vallejo, California
Posts: 4,049
It should not reflect any change. Try it and see if there is a difference.

DV captures at 0 IRE. It is the spec and there is nothing you can do about it. The 7.5 should only apply to analog video out.
__________________
Mike Rehmus
Hey, I can see the carrot at the end of the tunnel!
Mike Rehmus is offline   Reply With Quote
Old November 24th, 2004, 12:33 PM   #3
Regular Crew
 
Join Date: Mar 2004
Location: Palo Alto, CA
Posts: 55
Mike is right about the DV spec mandating recording black at 0 IRE. Unfortunately, the PD150/170 is among a handful of prosumer camcorders that PRINT TO TAPE black at 7.5 IRE if you flip on the "setup" feature in the menu. I learned this the hard way when I first shot with this cam. I ended up having to bring the black levels down on my captured footage. (I had turned setup to "on".)

The good news is that if you accidently do this, the cam does the equivalent of "adding brightness", so you don't lose much in terms of image information since information is still captured above 100IRE and not clipped. Everything is just digitally moved up by 7.5 IRE. The bad news is that you have a bit of extra work in post to fix this.

If you want more information on 7.5 IRE setup, Adam Wilt has written a lengthy FAQ on it, including a section (last one on the page) about cams like the PD150/170, et. al., which I wish I had read before that shoot:

http://www.adamwilt.com/DV-FAQ-tech.html#Setup
Harris Ueng is offline   Reply With Quote
Old November 24th, 2004, 01:37 PM   #4
Wrangler
 
Join Date: Dec 2002
Location: Mays Landing, NJ
Posts: 11,542
This raises an interesting question about setup and the analog s-video output. When I edit I use firewire output through a DVD recorder which transcodes to component video to drive my monitor. I have calibrated my monitor for this arrangement. However when I capture video using either my VX-2000 or PDX-10, I send s-video from the camera to the same DVD recorder which converts to compenent for the monitor.

I notice that the s-video from the camera is significantly darker, and assume that this is because the Sony camera's are outputting at 0 IRE black level instead of the 7.5 analog standard. Am I correct in this assumption? Too bad that the setup menu item doesn't behave as Mike suggests, it would be nice to add it to the analog port. I'm curious as to why it isn't already using a 7.5 analog black level too, makes it a problem if you want to dub directly from the camera to VHS.
Boyd Ostroff is offline   Reply With Quote
Old November 24th, 2004, 01:39 PM   #5
Wrangler
 
Join Date: May 2002
Location: Vallejo, California
Posts: 4,049
The reason for the switch is because in Japan, the legal IRE lower limit is 0
__________________
Mike Rehmus
Hey, I can see the carrot at the end of the tunnel!
Mike Rehmus is offline   Reply With Quote
Old November 27th, 2004, 06:30 PM   #6
Regular Crew
 
Join Date: Sep 2002
Location: St. Paul, MN USA
Posts: 151
Black Level

Boyd, maybe somewhere in my lengthy note is a clue to what you are seeing. I recently began burning DVD's from VX2000 captured footage. I noticed DVD colors looked "washed out" when I played DVD on stand alone DVD player compared to just outputting DV tape from camcorder to S-VHS input on same TV that plays the DVD. An article by Bob Hudson at www.signvideo.com explained as other notes in this thread note that USA analog inputs designed for 7.5 IRE whereas most DV camcorders output 0 IRE. Most DVD players in US however output 7.5 IRE. Anyhow, consequence of all this is that DVD's burned from DV tapes (I use Pinnacle's Liquid Edition non-linear editor) will consequently looked "washed out" or brighter. The article says this brighter output from DVD is actually closer to what camera actually shot since most DV camcorders tend to overexpose. I am still experimenting with various settings in Liquid Edition post editing to adjust gamma and black level and saturation on material I am burning to DVD---if anyone has found a good combination of settings please post it. Looking forward to reading the Adam Wilt article as his articles are great.
Dennis Hull is offline   Reply With Quote
Old November 28th, 2004, 01:03 PM   #7
RED Problem Solver
 
Join Date: Sep 2003
Location: Ottawa, Canada
Posts: 1,365
Digital video doesn't have any IRE. There's no such thing in digital video as IRE is an Analogue measure of voltage.

A fully digital workflow is the same the world over, with the same black and white levels, wether you're shooting DV, DVCpro50, DigiBeta, HDCAM etc. etc. As long as you don't convert to analogue or from analogue, you're fine. In that respect the 7.5 IRE switch on the Sony cameras is wrong as it raises recorded blacks from digital 16 (the correct number) to 32 which is WRONG.

If you need to add setup to the output of a DV camera for dubbing to VHS etc. then buy and use a proc amp.

A DVD player adds setup on it's analogue outputs. It is, however, a digital device so you should never raise your blacks from your DV camera edit in your NLE.

If you're monitoring through a DV camera, then just calibrate your monitor to the camera and NLE - don't worry about setup. Setup is just a brightness control, so by altering the brightness on your monitor, you're doing the same as a proc amp, and you can calibrate to the PLUGE bars. Similarly, burn a testcard easter egg onto your next DVD, and use that to calibrate your DVD monitor.

Graeme
Graeme Nattress is offline   Reply With Quote
Old November 28th, 2004, 02:14 PM   #8
Regular Crew
 
Join Date: Sep 2002
Location: St. Paul, MN USA
Posts: 151
Adjusting DVD

Graeme, I guess I just "discovered" the obvious when I noted the "washed out" look commonly observed when burning DVDs as output media for DV footage (re the article I referenced in my earlier post). Given all the digital/analog conversions and various conversion codecs that can occur from subject matter to output media (including various settings on TV's used by viewing audience) it is not unusual to get different "looks." The Sign Video website/store I mentioned does indeed suggest and sell process amps. I know those involved full time in this industry (I am just a hobbyist) adjust media in post to get different looks hence my experiments in different settings to get darker richer look I was used to even if not exactly what camcorder recorded. Since I output to VHS as well as DVD (now) for various friends I am making change in post rather than adjusting VX2000 settings.
Dennis Hull is offline   Reply With Quote
Old November 28th, 2004, 02:42 PM   #9
RED Problem Solver
 
Join Date: Sep 2003
Location: Ottawa, Canada
Posts: 1,365
If you're going to DVD, you'd have to adjust the video differently to VHS if you're trying to get black levels right. Best to leave black levels correct for digital and as anyone who watches a VHS is used to VHS looking bad, and that any black output on a VHS deck is not likely to be accurate anyway, it could look just as bad if the black is right as it is when it's wrong.

Graeme
Graeme Nattress is offline   Reply With Quote
Old November 28th, 2004, 07:53 PM   #10
Regular Crew
 
Join Date: Sep 2002
Location: St. Paul, MN USA
Posts: 151
Black Level

Graeme, Good points. As the article I referenced earlier says (at least I think it says) the DVD that looks ''washed out" is actually the more realistic portrayal of what the VX2000 shot and shows more detail in shadows. It just does not appear to have the darker (although less accurate) colors that I was used to when viewing DV tape from DV camcorder plugged into NTSC TV monitor (due to O IRE analog out from DV camcorder into 7.5 IRE tuned analog inputs of NTSC monitor). Since beauty is in eye of beholder I have been fiddling slightly with color settings in NLE just to see how DVD's burned after color setting adjustments look when played back on DVD players. However, since color settings vary on TV sets from person to person who knows how it will look at some friends/relatives homes.
Dennis Hull is offline   Reply With Quote
Old November 28th, 2004, 08:46 PM   #11
Wrangler
 
Join Date: Dec 2002
Location: Mays Landing, NJ
Posts: 11,542
Re: Black Level

<<<-- Originally posted by Dennis Hull : It just does not appear to have the darker (although less accurate) colors that I was used to when viewing DV tape from DV camcorder plugged into NTSC TV monitor -->>>

But if you properly calibrate your monitor to the camera's s-video port this shouldn't be a problem, as Graeme suggests.

I'm still a little confused as to why the s-video port on the PD-150, PDX-10, et al don't add the 7.5 IRE setup like a DVD player would however. But it isn't a big deal for me one way or the other. When I make VHS copies I do them from DVD's using s-video from the DVD player to a VHS recorder - this also provides the letterbox for my 16:9 footage without having to render a separate version.
Boyd Ostroff is offline   Reply With Quote
Old November 28th, 2004, 10:03 PM   #12
Wrangler
 
Join Date: May 2002
Location: Vallejo, California
Posts: 4,049
Everything I send to my VHS or S-VHS decks goes through a proc amp monitored by a waveform monitor. That way I can adjust setup if needed.

Ignoring the principles of making the best video tape possible, given the circucmstances isn't a very good idea. Most of my customer's televisions are not adjusted correctly but that doesn't mean one should deliver anything but the best possible recording.
__________________
Mike Rehmus
Hey, I can see the carrot at the end of the tunnel!
Mike Rehmus is offline   Reply With Quote
Old November 28th, 2004, 10:10 PM   #13
Regular Crew
 
Join Date: Mar 2004
Location: Palo Alto, CA
Posts: 55
Hey Boyd, this is in reply to your question...

The most plausible answer I've heard about why these cams don't simply add setup on the analog outputs is that this is one feature out of an entire set that Sony uses to differentiate these cam's on the feature-set side of things from the DSR-250's, 390's, 570's, et al. This way, Sony creates sufficient product differentiation across the line so that they can continue to justify the substantially higher cost of their pro cam's and continue to recoup development costs. The 150/170's already are diverting more attention than Sony would like from up the product line, so they really need to "design-in" per se, certain features that maintain that differentiation. You gotta admit, these puppies do a lot for the price.

Another reason it's not a priority feature with these cams is because NTSC in the US/Canada/Mexico is the only standard that requires setup at 7.5 IRE, while the rest of the world is on PAL or an international version of NTSC, which, as Mike pointed out, specs black levels out at 0 IRE. A digital implementation of adding a few bits to the data stream is a lot easier than implementing an independent analog fixed brightness circuit with digital controls. Think cost savings and simplified circuit architecture.

Whether these have been the right places to draw the lines or not is debatable, but that's what was done in the corporate circles, and that's what we're living with now.

Now, this is mostly talk with other people outside the walls of Sony Corp., since I don't work for their product marketing team, nor for Sony at all, for that matter, it's just an educated guess.
Harris Ueng is offline   Reply With Quote
Old November 29th, 2004, 05:52 AM   #14
RED Problem Solver
 
Join Date: Sep 2003
Location: Ottawa, Canada
Posts: 1,365
Also, add in the fact that in an all digital environment, IRE is a none issue, and you can see Sony's point of not spending any money to do it "right". Boyd, you're idea of making the VHS from the DVD is best of all. And you're right that calibration of the monitor to the system is the important one. Do that and you're A-ok fine.

Mike, you're right that you should make the best VHS you can, but I must admit that because I'm in a dual standard environment with moving to Canada from England, and have PAL and NTSC VHS S-VHS tapes, I'm always adjusting brightness levels anyway, and in every place I've ever seen VHS used, the TVs are so far off calibration I've never thought that the 0 or 7.5 IRE would make enough difference to warrant worrying about or spending money to put right. After all, 7.5IRE is no longer needed for you to avoid seeing the flyback on TV or whatever it was designed to "fix", so it's just a brightness control now. OK - enough justifying my lazyness... Perhaps I'm just PAL at heart.

Graeme
Graeme Nattress is offline   Reply With Quote
Old November 29th, 2004, 07:49 AM   #15
Wrangler
 
Join Date: Dec 2002
Location: Mays Landing, NJ
Posts: 11,542
Harris: thanks, your ideas seem to ring true.

Graeme, I have to agree on a practical level with your sentiments about VHS, although Mike is of course right about the need to take pride in your work and produce the best quality end product. However during the past year I've only recorded two T-120 tapes. These were archive tapes provided to a director by request because he didn't have a DVD player. I just made those tapes a couple days ago, and I had forgotten just how bad VHS looks! I'm sure some of this has to do with my VCR, although it does have s-video in/out and can record s-vhs. If I was making lots of VHS tapes for paying clients then I think Mike's approach would be the way to go.
Boyd Ostroff is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Sony XAVC / XDCAM / NXCAM / AVCHD / HDV / DV Camera Systems > Sony HDV and DV Camera Systems > Sony VX2100 / PD170 / PDX10 Companion

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 02:17 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network