abrupt highlights clipping

[Piotr Wozniacki]

Originally Posted by Michael H. Stevens

Very good point Piort. I knew this and totally forgot the problem of the Zebra #1 95 being 90-100.

Actually, it will appear everywhere between 85 and 105%, Mike.

Originally Posted by Michael H. Stevens

Maybe, if you set Zebra #1 to 100, then when zebras FIRST appear you are at 95?????????

It will then appear between 90 and 110%.

None very useful for highlight clipping control. Very good for your main subject (e.g. human skin) controlled exposure.

[Piotr Wozniacki]

I think I should add that I find the solution of Zebra1/Zebra2/histogram very useful and properly thought-through by Sony.

- zebra 1 for controlling your main subject exposure (e.g. face skin at around 70%), and only activated when needed (to avoid cluttering of the VF)

- zebra 2 fixed at 100% and always on, to control and prevent clipping when possible

- histogram: this is a bit more complicated, but also works properly. For example, with Cine2 it will never go to the very RH end (zebra 2 is never triggered within the resonable overal exposure of your scene). So, how can one control the highlights exposure? Well, just try this: overexposure by 2-3 stops and - even though the Zebra 2 is still absent - you will notice a vertical bar at the RH end of the displayed histogram range (NOT at 100% - a bit to the left of it). This is because Cine2 will compress highlights enough to never exceed 100% - now turn the exposure down, and you will see this vertical bar going down... Try to make its hight more balanced with the rest of your histogram, and you'll be fine.

With the STD1 being the opposite extreme, the vertical bar can appear at the most RH end of the histogram scale, which of course is confirmed by the Zebra 2: you're clipping at over 100%.

[Michael H. Stevens]

Originally Posted by Piotr Wozniacki

- you will notice a vertical bar at the RH end of the displayed histogram range (NOT at 100% - a bit to the left of it). This is because Cine2 will compress highlights enough to never exceed 100% - now turn the exposure down, and you will see this vertical bar going down... Try to make its hight more balanced with the rest of your histogram, and you'll be fine.

.

Thanks Piotr: I have been taking that vertical line right down to zero when using the histogram. I'll try your way.

[Piotr Wozniacki]

Originally Posted by Michael H. Stevens

Thanks Piotr: I have been taking that vertical line right down to zero when using the histogram. I'll try your way.

There's certainly no reason to take it down to zero, Mike - it represents pixels with completely legitimate exposure (brighness) value! Of course, I'm talking now about the cine gammas, which generally prevent from clipping above 100% - compressing everything gracefully much "to the left" of 100% (especially the Cine2 gamma).

[Piotr Wozniacki]

Reading about the ongoing problems that so many users have with their camera's vignetting and/or backfocus, I'm thinking the "abrupt highlights clipping" can indeed be treated as a "peculiarity" rather than a flaw...

On the other hand, while the vignetting (or even backfocus, as it seems to depend on the ND filter use) might be difficult to fix (the worst scenario being they're inherent in the design's tight tolerances, and/or ND filter implementation) - the knee/hightlight compression algorithm is a purely software issue, so I'll appreciate input from people like Adam Wilt or Leonard Levy or Tom Roper, who appreciate this problem - it would help greatly in articulating our wishes for some future firmware update in this regard.

[Randy Strome]

Originally Posted by Piotr Wozniacki

There's certainly no reason to take it down to zero, Mike - it represents pixels with completely legitimate exposure (brighness) value! Of course, I'm talking now about the cine gammas, which generally prevent from clipping above 100% - compressing everything gracefully much "to the left" of 100% (especially the Cine2 gamma).

Really only Cine 2 will limit to 100%. On 1, 3 and 4, the curves will deal with the rolling of the whites nicely under 100%, but rescuing whites above 100 can be more work. I think Michael was on the right track. Find Zebra 100, and back off till none. Then use the black level that best pulls the histogram (or waveform) to your floor.

This is what I am considering pushing right "with safety" on this camera.

[Piotr Wozniacki]

Originally Posted by Randy Strome

Find Zebra 100, and back off till none.

Exactly what I've been saying (and doing), Randy.

[Bill Ravens]

holy mother of God! I've said that since day 1!
http://www.dvinfo.net/conf/showthrea...=110902&page=9 see post no. 128
Welcome to the club.

[Piotr Wozniacki]

But so have I, Bill - like here: http://www.dvinfo.net/conf/showpost....&postcount=174

"- if in manual iris mode, with zebra set to 100%, never allow ANY zebra in the sky (some traces only allowed in pure white areas, like birch barks; the sky - even cloudy - is NEVER pure white so NO zebra there!)"

[Michael H. Stevens]

Me too....

..................................................

[Michael H. Stevens]

Originally Posted by Randy Strome

Really only Cine 2 will limit to 100%. On 1, 3 and 4, the curves will deal with the rolling of the whites nicely under 100%, but rescuing whites above 100 can be more work. I think Michael was on the right track. Find Zebra 100, and back off till none. Then use the black level that best pulls the histogram (or waveform) to your floor.

This is what I am considering pushing right "with safety" on this camera.

JUST SO THERE IS ABSOLUTELY NO CONFUSSION do you mean "black level" and not "black gamma"? If you DO mean "black level" what do you do, if anything, with "black gamma"? Is that just for the internal strech - ie detail vs noise?

[Piotr Wozniacki]

"Black" shifts the middle (gray) level of the gamma curve, while "Black gamma" is responsible for what on many prosumer cameras is called Black Stretch/Compress.

My experience from the much less light-sensitive (and hence noise-prone) V1 us that if noise is potentially a problem, you'll be better off crushing the blacks to get rid of it (along with details in dark areas, but I personally prefer such picture than a stretched one, with lots of detail and chroma noise).

[Michael H. Stevens]

Originally Posted by Piotr Wozniacki

"Black" shifts the middle (gray) level of the gamma curve, while "Black gamma" is responsible for what on many prosumer cameras is called Black Stretch/Compress.

My experience from the much less light-sensitive (and hence noise-prone) V1 us that if noise is potentially a problem, you'll be better off crushing the blacks to get rid of it (along with details in dark areas, but I personally prefer such picture than a stretched one, with lots of detail and chroma noise).

Piotr: I know quite well what Black Level and Black Gamma are I was asking Randy wht settings he used.

[Piotr Wozniacki]

Oh, sorry - was reading too fast :)

[Randy Strome]

Originally Posted by Piotr Wozniacki

"Black" shifts the middle (gray) level of the gamma curve, while "Black gamma" is responsible for what on many prosumer cameras is called Black Stretch/Compress.

There are a lot of settings, and as always I claim no expertise. That said, my understanding is different than Piotr's.

I think visually, so in terms of curves:

Black level, (called just "Black" in PP) is your master black and sets only the black point. Middle Gray is shifted by "Gamma". "Black Gamma" Would be like setting a point on the lower region of the curve and adjusting from there.

I have been leaving the Gamma and Black Gamma settings alone, but I am sure I will start to meddle with those too.