Black Gamma and Noise.

[Keith Moreau]

Alister, thanks for taking the time for the explanation,. I think it makes sense to me now. I also do audio and your explanation is akin to turning up your electric guitar as hot as you can and then reducing the signal down at the mixing console, the noise floor is reduced. I guess if you want to keep your recorded levels below what is possible then the brick wall is ok and you don't have to deal with superwhites in post.

Do we all know scientifically for a fact that -3db actually results in lower noise for a given signal level, up to the point where it hits the brick wall other than the assumptions about what is going on with -3db vs 0db?

Bill, I've tried adjusting the black level but no matter what I do I can't get the left side brick wall to go away, I can get it to move the wall to the right but not all the way to the left.

Thanks all again for the good info.

[Alister Chapman]

I can see the differences in noise in my images between 0db and -3db.

[Michael Maier]

Originally Posted by Alister Chapman

Crisping sets the level at which detail correction is applied to the image. My trials indicate that increasing the crispening to a positive value makes the camera apply less detail correction to low contrast areas of the image. From my experiments I have decided that a value of +20 to +30 helps control noise in darker areas. It's not a massive difference but it does help.

Interesting findings, specially given the BBC tests produced very different recommendations. The BBC tests recommend a crispening setting of -45. What’s your opinion on that Alister?


By the way, any new findings on the cinema matrix use?

Also, when you use the matrix set to cinema, do you use all factory default settings for Level, Phase and color settings (R-G, R-B, G-R etc) or do you use Bill’s TC3?

Thanks.

[Simon Wyndham]

The BBC tests recommend a crispening setting of -45.

There is a big difference in aims between what Alister is aiming for in his PP and what Alan Roberts was. Roberts is aiming for as close to a scientific replication of the way film handles detail.

You will notice that Alan reduces the detail right down, so the crispening gives some compensation to this. It would be more useful if the EX included a Level Depend setting.

One thing to be careful of with the cinegammas is shooting interview shots. Better to use STD gammas for such shots since the cines can compress those tones in a not very nice manner. I prefer Cine 4 out of all of them.

[Michael Maier]

Originally Posted by Simon Wyndham

There is a big difference in aims between what Alister is aiming for in his PP and what Alan Roberts was. Roberts is aiming for as close to a scientific replication of the way film handles detail.

You will notice that Alan reduces the detail right down, so the crispening gives some compensation to this. It would be more useful if the EX included a Level Depend setting.

Hi Simon. Not really sure I understand what you mean above.

Originally Posted by Simon Wyndham

One thing to be careful of with the cinegammas is shooting interview shots. Better to use STD gammas for such shots since the cines can compress those tones in a not very nice manner. I prefer Cine 4 out of all of them.

Cine4 if you would "have" to shoot an interview with a cinegamma or for general use? I find Cine1 to be best in handling high contrast scenarios like day externals with shadows than Cine4. I like Cine 4 for low light.

[Michael Maier]

Hi Simon, I'm still interested in your reply :)

[Alister Chapman]

I can't work out why Alan suggests setting crispening to -45. It increases noise in the shadows. I know Alan did not spend a large amount of time with the camera and didn't find many things such as the difference in cinegamma peak levels at different gain settings and differences in noise with different gammas.

With all these settings there is no right or wrong way to set the camera up. Different people and different projects will have different needs and want different things from the camera. For many years European broadcast cameras were set up according to a setting called EBU75, developed by the BBC and EBU. The whole idea behind this setting was not to get the best out of the camera, but to provide a setting that restricted the gamut to a level that could be displayed on even the cheapest of CRT TV sets without any artifacts. Sadly the BBC's standard HD setup is still largely based on the old EBU75 setup, restricting the colour range to around 75% of what is perfectly legal for broadcast.

I almost always use the cinema matrix at +30 as at 0 the chroma levels are way down.

I also completely agree with Simon about not using cinegammas for interviews as even the slightest over exposure of skin tones will not look natural.

[Serena Steuart]

Crispening affects the lower luminance regions of the image where you find noise.Giving it a positive value ensures that detail isn't applied to noise, and the higher the value the higher the threshhold at which sharpening is applied. To quote Sony:
"Crispening is a function that prevents detail signals being generated around noise or small picture edge transitions, when the DETAIL function is set on. This allows you to select the threshhold (based on transition level) of picture edge transitions to which detail signals should not be added. "

[Michael Maier]

Makes sense Alister.
Maybe the BBC setting is a typo and he really meant +45?
Maybe somebody who knows him should ask. If it's a typo it needs to be corrected. Noise is a big thing.

Although I tend to agree with the BBC settings in using the cinema matrix if you are shooting drama or want to emulate film or are going to filmout. The normal matrix is too saturated for that, looks more like TV in most cases.

[Simon Wyndham]

Crispening affects the lower luminance regions of the image where you find noise.Giving it a positive value ensures that detail isn't applied to noise, and the higher the value the higher the threshhold at which sharpening is applied.

No. Crispening affects the whole image. The Level Depend function that I mentioned earlier that appears on higher priced cameras would enable tuning of the luminance level at which detail is applied.

I can't work out why Alan suggests setting crispening to -45. It increases noise in the shadows.

True, very true. But I think the reason is that Alan doesn't aim to perform functions such as reducing noise. He actually aims for the opposite, to eliminate as much as he can the electronic processing while using some functions to subtly get the result he wants. *However* like Alister I do not always agree with the settings that Alan comes up with. He rarely gets the time he needs to do these setups with any degree of fine tuning, by his own admission.

[David C. Williams]

http://pro.sony.com/bbsccms/assets/f..._Sharpness.pdf

Not specifically the EX, but Sony jargon stays fairly consistent.

[Serena Steuart]

Originally Posted by Simon Wyndham

No. Crispening affects the whole image.

Gosh, Sony don't understand their crispening function!

[Simon Wyndham]

Originally Posted by Serena Steuart

Gosh, Sony don't understand their crispening function!

No, they understand it perfectly. Read again the quote you gave from the Sony description

"This allows you to select the threshhold (based on transition level) of picture edge transitions to which detail signals should not be added."

That description is not talking about luminance levels, but edge frequency. The crispening function tunes the point at which the detail circuits kick in. By tuning the crispening you can fine tune things to make sure that the camera is not applying any detail correction to the noise in the picture at all levels of luminance.

The Level Depend adjustment found on cameras like the PDW-700, 510, 530 etc allows you to adjust the luminance level at which the detail correction kicks.

The function is explained here http://pro.sony.com/bbsccms/assets/f...Dark_Areas.pdf

[Serena Steuart]

Ok!............

[Bob Grant]

Would not the Black Limiter setting in Detail achieve what you're looking for?