Black blacks at DVinfo.net

Bob Grant · November 5th, 2010, 07:16 PM

I had an EX camera hooked up to a Panny monitor yesterday and looking at the waveform monitor I found it was impossible to get absolute black, even with the lens hood and iris closed. Changing Black in the PP to -5 to -10 solved the problem. I had a dead straight line with no dancing noise.
Opening the lens hood and iris I didn't notice any harm being done to the image. That is a based on a very quick eyeball though.
I typically do the exact same thing in post to reduce the noise level and save bandwidth for whatever I'm encoding to, doing the same in camera to save bandwidth seems logical enough to me. Anyone think of a reason why I should not leave Black set at -5?

Piotr Wozniacki · November 6th, 2010, 03:45 AM

Bob,

Based on the same observations/experience, I've had all my PP's with negative Black levels since the very early days of using my EX1. The exact value depends on the Gamma curve used in a given PP, but it usually is in the same range of -5 down to -10.

Piotr

Bob Grant · November 6th, 2010, 06:37 AM

Thanks Piotr.
In the past I've wound black gamma down a bit to push the noise down. Next time I have to shoot a lot of black I'll try the alternative of dialing Black down a bit.

Leonard Levy · November 7th, 2010, 01:23 AM

It may vary with the gamma you're using, but I've had my black at -6 ever since I got the EX-1. I use standard gamma 3. I don't know why they set 0 so high. The HVX did that also. On the HVX if you were shooting with 7.5 set up added, I think black at 0 was correct at 7.5, but if you went to 0 set-up, the Black would only go down to 5 IRE or so. Thus I also ran my blacks somewhere from -4 to -6.

I think that should be the correct way to shoot for maximum tonal values and bandwidth. You don't actually gain any information if you run the black higher, you just wash out the picture. If you want to gain grey scale down there do it with the black stretch or black gain - whatever they call it. Black should be black and that's around -5 or -6.

David Issko · November 8th, 2010, 02:09 PM

Quote:

Originally Posted by Bob Grant

Changing Black in the PP to -5 to -10 solved the problem. Anyone think of a reason why I should not leave Black set at -5?

Bob,

Checking & adjusting the black levels on my EX3 & PMW-350 was one of first things I did to my cameras. Both needed to be set down a little to the same waveform setting as you have. Not sure of the numbers but -3 to -5 rings a bell.

I have kept them there ever since and periodic checks reveal that they are sitting nicely at those settings.

I have never encountered any issues with either camera since adjusting the settings downwards.
Cheers

Olof Ekbergh · November 8th, 2010, 03:17 PM

On cinegamma 4 my standard settings are:
Black -3
Black Gamma -2

I also set detail to -10

I think all cameras need some dialing in. Scopes and good calibrated monitors makes this much easier. Modern eval monitors now come with scopes included a real money saver.

November 5th, 2010, 07:16 PM	#1
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	Black blacks I had an EX camera hooked up to a Panny monitor yesterday and looking at the waveform monitor I found it was impossible to get absolute black, even with the lens hood and iris closed. Changing Black in the PP to -5 to -10 solved the problem. I had a dead straight line with no dancing noise. Opening the lens hood and iris I didn't notice any harm being done to the image. That is a based on a very quick eyeball though. I typically do the exact same thing in post to reduce the noise level and save bandwidth for whatever I'm encoding to, doing the same in camera to save bandwidth seems logical enough to me. Anyone think of a reason why I should not leave Black set at -5?

November 6th, 2010, 03:45 AM	#2
Piotr Wozniacki Inner Circle Join Date: Aug 2006 Location: Poland Posts: 4,086	Bob, Based on the same observations/experience, I've had all my PP's with negative Black levels since the very early days of using my EX1. The exact value depends on the Gamma curve used in a given PP, but it usually is in the same range of -5 down to -10. Piotr __________________ Sony PXW-FS7 \| DaVinci Resolve Studio; Magix Vegas Pro; i7-5960X CPU; 64 GB RAM; 2x GTX 1080 8GB GPU; Decklink 4K Extreme 12G; 4x 3TB WD Black in RAID 0; 1TB M.2 NVMe cache drive

November 8th, 2010, 03:17 PM	#6
Olof Ekbergh Sponsor: Westside AV Join Date: Dec 2008 Location: Mount Washington Valley, NH, USA Posts: 1,365	On cinegamma 4 my standard settings are: Black -3 Black Gamma -2 I also set detail to -10 I think all cameras need some dialing in. Scopes and good calibrated monitors makes this much easier. Modern eval monitors now come with scopes included a real money saver. __________________ Olof Ekbergh • olof@WestsideAV.com Westside A V Studios • http://www.WestsideAVstore.com/

November 6th, 2010, 06:37 AM	#3
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	Thanks Piotr. In the past I've wound black gamma down a bit to push the noise down. Next time I have to shoot a lot of black I'll try the alternative of dialing Black down a bit.

November 7th, 2010, 01:23 AM	#4
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	It may vary with the gamma you're using, but I've had my black at -6 ever since I got the EX-1. I use standard gamma 3. I don't know why they set 0 so high. The HVX did that also. On the HVX if you were shooting with 7.5 set up added, I think black at 0 was correct at 7.5, but if you went to 0 set-up, the Black would only go down to 5 IRE or so. Thus I also ran my blacks somewhere from -4 to -6. I think that should be the correct way to shoot for maximum tonal values and bandwidth. You don't actually gain any information if you run the black higher, you just wash out the picture. If you want to gain grey scale down there do it with the black stretch or black gain - whatever they call it. Black should be black and that's around -5 or -6.