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Question: Relationship between Chroma Subsampling and Bit Depth?

 
Author desmondqford
ZRO
#1 | Posted: 28 Aug 2012 15:34 
How is chroma subsampling related to bit depth?

I mean, if you have RGB 444 at 8 bits, versus RGB 422 at 12bits, what is the difference? I know that RGB444 at 12 bits is about as good as it gets, but is actually happening here?

How do the two interplay, or what is the difference between them?

My apologies for the newbie questions. Kindly explain in layman's terms.


Thanks a lot... This forum has been a major help in my color education!

DF

Author Steve

INF
Male
#2 | Posted: 28 Aug 2012 17:54 
desmondqford:
How is chroma subsampling related to bit depth?

It's not... The two are not related at all.

Chroma sub sampling is a form of compression that only affects colour.
It is actually a lot like a Bayer sensor, which a lot of supposed RGB 444 cameras use, so all is often not as it seems.
There is a lot more behind your question than a simple reply can answer.
When I have more time I'll try to expand on this, but I'm sure others can add info as well
Steve Shaw
Mob Boss at Light Illusion

Author desmondqford
ZRO
#3 | Posted: 28 Aug 2012 19:48 | Edited by: desmondqford 
Thanks for the response.

On set I keep coming across people mixing and misusing terms... as mentioned in another post regarding gamma and color spaces. Now it seems that I'm one of them! For example, producers often ask if a camera has a big enough color space to get the image they want, but if I understand color spaces correctly, that question makes no sense...

Truly understanding the actual science behind what is happening while filming in regard to color, light, sensors, debayering, etc... is mind-boggling. I've always thought that it would make me a better filmmaker, but it seems to just complicate things and make me question my gut...

I've only met a handful people in person (all brilliant DITs) that can actually explain these things, yet I've worked with hundreds of people on set...

Thanks again, Steve. You're awesome!

Author Steve

INF
Male
#4 | Posted: 29 Aug 2012 18:10 
I have to say that being knowledgeable about how cameras work actually rarely makes for better images...

This is 'Show Business', not a 'Let's use the most technology' industry - pictures should just look good, and often the technology has nothing to do with it.

Most cameras have a WYSIWYG capability, or at least quick and easy on-set review capability - that means there is no real excuse for poorly captured images any more.

It's a major reason why the recent dick swinging from various camera manufacturers makes me smile. There really isn't much difference, if the images are just checked during shooting - the results are usually all very good.

Steve
Steve Shaw
Mob Boss at Light Illusion

Author Jay Friesen
ZRO
#5 | Posted: 1 Sep 2012 14:08 | Edited by: Jay Friesen 
Subsampling is how. Camera does its "thing." Well beyond my expertise or even desire to understand. Bit depth or color depth is a bit easier to manage and makes my life much better the more I have . Adobe actually has a decent explanations but because Steve has a nifty anti-spam policy, I can't post the links so I'll copy/paste:

"Color depth (or bit depth) is the number of bits per channel (bpc) used to represent the color of a pixel. The more bits for each RGB channel (red, green, and blue), the more colors each pixel can represent."

"Bit depth specifies how much color information is available for each pixel in an image. The more bits of information per pixel, the more available colors and more accurate color representation. For example, an image with a bit depth of 1 has pixels with two possible values: black and white. An image with a bit depth of 8 has 28, or 256, possible values. Grayscale mode images with a bit depth of 8 have 256 possible gray values.

RGB images are made of three color channels. An 8‑bit per pixel RGB image has 256 possible values for each channel which means it has over 16 million possible color values. RGB images with 8‑bits per channel (bpc) are sometimes called 24‑bit images (8 bits x 3 channels = 24 bits of data for each pixel)."

Chromo subsampling is how the camera takes this info off the sensor

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 Question: Relationship between Chroma Subsampling and Bit Depth?

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