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elveto
08-02-2011, 12:08 AM
hi,
i'm working on a low key 3d short as a solo project where dark area's should remain hidden for the audience.
Now that i rendered and cut most of the film i noticed that certain software players, or HD television screens (in my case with internal player via usb) blow up the gamma quite alot so all the dark area's become exposed thus revealing the whole scenery. This kills the mood and story completely.

I looked at the 'YC waveform' in premiere and saw that all dark area's are close to the 0.3 margin what seems to be 100% black (after testing with a pure black image) but not completely. They are more like 0.33. I can't imagine that this small percentage could have such an affect.

A friend told me that this is due the fact that they are rendered images, thus having 100% color info per pixel... so the overall image is always present even when 99% black. In other words dark area's don't get 'dropped' as pure black.

First off i dont want pure blacks, i like the little color/value differences when watched on a optimal screen/ player. How do i get the image to appear optimal on all players without losing quality?

thanks!

tested with 1920 x 1080 mp4 h264 video.
rendered in maya/3delight
sequenced & composited in adobe AE
cut in adobe premiere.

This will get played on computer/dvd/blueray/ via computer screen/ HD television/ HD projector etc..

evanfotis
08-02-2011, 08:41 AM
each output medium has differences depending on the hardware ability and calibration (projector, tv, monitor) and signal (pc:0-255, dvd:16-235).
Don't know if it what you're looking for but I'd apply a curves/levels adjustment to crush blacks and gradually restore them.

scrimski
08-02-2011, 12:44 PM
workaround for h264 gamma shift
http://forums.cgsociety.org/showthread.php?f=10&t=643310&

elveto
08-03-2011, 04:40 PM
each output medium has differences depending on the hardware ability and calibration (projector, tv, monitor) and signal (pc:0-255, dvd:16-235).
Don't know if it what you're looking for but I'd apply a curves/levels adjustment to crush blacks and gradually restore them.

Yes i can see your method, i'll use it if nothing more elegant turns up. thanks

elveto
08-03-2011, 04:54 PM
workaround for h264 gamma shift
http://forums.cgsociety.org/showthread.php?f=10&t=643310&

Doesnt affect the the fact that the gamma can get shift revealing the dark area's.

VLC doesnt even pick up this fix ??

WickedP
08-04-2011, 04:11 AM
The short answer to this is you're not going to get the best in both worlds without creating a video that suits each output type.

For computer screens etc you're standard renders will be fine with full 0-255RGB values. But for TV for instance, as evanfotis has eluded too, you'll need to create safe colours. In AE try this to all your footage (or use premiere):

Add an adjustment layer on top of everything. Add a levels filter effect to this layer. Change to following values:
Input Black 16
Input White 235
Gamma 1.00
Output Black 16
Output White 235

You will notice small changes on your computer screen - there's nothing you can do about that other than to bare in mind you're adjusting it for TV. When viewing on a TV screen your viewers, and any untrained eye for that, won't know the difference.

See how you go with that. Hope it helps!

WP.

elveto
08-04-2011, 06:24 AM
following values:
Input Black 16
Input White 235
Gamma 1.00
Output Black 16
Output White 235


WP.

Yes thanks for this hands on approach,
it does do the trick in uniforming the blacks although there is a big (and i mean big) loss of definition of objects shadows due a flattening effect. I take that 16 will appear totally black on a dvd to screen but what would happen when I stick to a black value of 5 which in my case shows best? (... dark area's are optimally crushed but objects remain defined.)

I know that I could compromise the lack of definition with another adjustment before the safe colors...

But I wonder what exactly would happen with the YUV (luma) to RGB expansion calculation?

16 => 0
5 => -11,9 ??
how would it handle it

thanks

WickedP
08-04-2011, 01:23 PM
Sorry I might have made an error in my first post. The method I suggested will clip the values at 16 I think, so you will lose definition in your darker areas below the 16 RGB value. They will simply be black.

Instead, try this:

Input Black 0
Input White 0
Gamma 1.00
Output Black 16
Output White 235

This way, your colour values should be 'scaled' instead of clipped to fit the broadcast rule. So, your shadows being 5, will become something like 19. My apologies for that, I should have picked up on that earlier.

As for the 'what might happen' scenario - I believe TV and broadcast will accept colours outside the safe zone (maybe -5% to 105%?) but I'm not sure what it would do if you did. Perhaps best avoid it if possible. Just to be safe.

WP.

scrimski
08-04-2011, 01:48 PM
As for the 'what might happen' scenario - I believe TV and broadcast will accept colours outside the safe zone (maybe -5% to 105%?) but I'm not sure what it would do if you did.
Illegal colors will get clipped( not that bad, but not ideal) or the whole luma range from 0 to 255 will get compressed into 16 to 236( very bad)


[QUOTE]I take that 16 will appear totally black on a dvd to screen but what would happen when I stick to a black value of 5 which in my case shows best? (... dark area's are optimally crushed but objects remain defined.)I would stick with black at 5 but lower the whites to 225 and lift the result back to 16 to 235. That way you keep the luma range but don't reveal the dark parts, keep the blacks uniform and don't lpose details(at least I hope so).

elveto
08-04-2011, 05:08 PM
ok guys,
I think we got it nailed.
here are the results, correct me if i did something wrong.

thanks again!

http://img41.imageshack.us/img41/6889/bwclippingsafecoloringf.png

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