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DPChallenge Forums >> Tips, Tricks, and Q&A >> 12-bit A/D conversion?
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 10/10/2005 03:39:54 AM · #1
"12-bit A/D conversion provides a finer tonal gradation" what does this means basically?
 10/10/2005 04:08:24 AM · #2
12bit=4096 steps potential steps from dark to light areas in an image.

8 bit = 256 steps..

Finer tonal gradation = Smaller/more steps from dark to light.

Sorta, in an oversimplified nutshell. :-).

Cheers, Me.

edit: jpeg=8bit, raw=12bit

Message edited by author 2005-10-10 04:09:15.
 10/10/2005 04:14:58 AM · #3
Originally posted by KiwiChris:
12bit=4096 steps potential steps from dark to light areas in an image.

8 bit = 256 steps..

Finer tonal gradation = Smaller/more steps from dark to light.

Sorta, in an oversimplified nutshell. :-).

Cheers, Me.

edit: jpeg=8bit, raw=12bit


Thanks! :)
So there is NO WAY Jpeg can contain 12bit of tonal data (dynamic range?)
but then some cameras have 12bit AD conversion in their hardware specs, but do not support RAW output. what gives?
 10/10/2005 04:33:10 AM · #4
Correct, jpeg is an 8bit per colour format. 24 bits per pixel.

The a/d reads in some cameras reads in the data in 12 bit and uses that information to create the 8 bit jpeg image. There is an advantage in using 12 bit processing as it allows the camera to do better in-camera white balance etc.

A camera with only 8 bit 'internals' would have trouble making fine adjustments to whitebalance, sharpening, contrast etc without horrendous artifacts showing in the output jpeg...

Cheers, Me.
 10/10/2005 05:00:51 AM · #5
Originally posted by KiwiChris:
Correct, jpeg is an 8bit per colour format. 24 bits per pixel.

The a/d reads in some cameras reads in the data in 12 bit and uses that information to create the 8 bit jpeg image. There is an advantage in using 12 bit processing as it allows the camera to do better in-camera white balance etc.

A camera with only 8 bit 'internals' would have trouble making fine adjustments to whitebalance, sharpening, contrast etc without horrendous artifacts showing in the output jpeg...

Cheers, Me.


SUPER! thanks for the clarification. wish i could mark your replies helpful :)
 10/10/2005 09:09:35 AM · #6
Originally posted by shadow:
Originally posted by KiwiChris:
12bit=4096 steps potential steps from dark to light areas in an image.

8 bit = 256 steps..

Finer tonal gradation = Smaller/more steps from dark to light.

Sorta, in an oversimplified nutshell. :-).

Cheers, Me.

edit: jpeg=8bit, raw=12bit


Thanks! :)
So there is NO WAY Jpeg can contain 12bit of tonal data (dynamic range?)
but then some cameras have 12bit AD conversion in their hardware specs, but do not support RAW output. what gives?


the size of the ADC (Analoge Digital Converter)is only one factor
255 level (12bit) DAC has 2.4 levels of dynamic range (log base 10)
4096 level (12bit) DAC has 3.6 levels dynamic range (log base 10)

what is missing is the linearity/log'arity of the sensor ....
you are only as good as your sensor AND ADC ...

(oh & skill is in there to .....;)

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