An interesting concept but I know nothing about JPEG-2000 other than it
exists and provides support for more than 8 bits (or so I thought, keep
reading).
I just decided to look it up in PhotoShop to see if it's even supported.
It is but only by installing a special plug-in (on the CS3
distribution CD but not installed by default). The PS help file gives a
fair amount of information about the file format and its control
parameters but says nothing about bit depth or how bits are treated.
Next I looked at the Wiki page. Not too much enlightenment there on a
single quick read. I think it will take me 10 readings (at least) to
understand it. No specific mention of bit depths at all which is very
confusing. But I think what you're referring to about "adaptive range
compression" may be the section on "quantization". It says:
"After the wavelet transform, the coefficients are scalar-quantized to
reduce the amount of bits to represent them, at the expense of a loss of
quality. The output is a set of integer numbers which have to be encoded
bit-by-bit. The parameter that can be changed to set the final quality
is the quantization step: the greater the step, the greater is the
compression and the loss of quality. With a quantization step that
equals 1, no quantization is performed (it is used in lossless
compression)."
Anyhow, I can see that JPEG-2000 is very, very computationally
intensive. I can see why it has yet to show up on a camera near me. :-)
Chuck Norcutt
On 9/19/2010 12:26 PM, Jan Steinman wrote:
>> From: Chuck Norcutt<chucknorcutt@xxxxxxxxxxxxxxxx>
>>
>> If you shoot JPEG only, the 10 stop dynamic range you mention below
>> cannot be contained within a JPEG which has, theoretically at
>> least, an 8 stop range.
>
> Is this still true with JPEG-2000? I thought it had adaptive range
> compression -- in other words, a bit is not restricted to a doubling,
> but could be 2.5 times, for example.
>
> ---------------- When you blame others, you give up your power to
> change. -- Robert Anthony :::: Jan Steinman, EcoReality Co-op ::::
>
--
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