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[OM] Re: Scan sizes, was Unbelievable Conversion on OM 2S

Subject: [OM] Re: Scan sizes, was Unbelievable Conversion on OM 2S
From: Chris Barker <ftog@xxxxxxxxxxxxxxxx>
Date: Mon, 5 Apr 2004 06:29:46 +0100
Parzival

Thanks for the hint about PNG.  I came across this format only when I 
started using Fireworks, and I thought it was a bit of a distraction.  
However, I now see that it is smaller than TIF.

Chris

On 1 Apr 2004, at 20:44, Parzival Herzog wrote:

>
> On April 1, 2004 11:45, Chris Barker wrote:
>> When you use this format, you have the choice of qualities or
>> 'lossless'.  I should have expected that to fulfill its description.
>> Are you telling me that this dialogue box is an out and out liar? ;-)
>
> The, JPEG 2000 file format includes a lossless option., in which 
> residual
> error from the main image compression result is also stored. Of 
> course, if
> your program is not doing it correctly, then its dialog box may indeed 
> be
> lying. Its easy to check though: Compress your image file with Jpeg 
> 2000 then
> expand in your image processing program, subtract expanded image from 
> the
> original, and you will get the error image. This will appear black 
> until you
> expand its (hopefully minuscule) tonal range to full scale. Lossless 
> will
> stay black, as there is no tonal range.
>
> Try this with the same image compressed to the same compressed file 
> size,
> using jpeg and jpeg2000. You should see that for most photographic 
> images
> jpeg2000 is indeed much better, and the error is generally well below 
> the
> noise inherent in the photographic image (although it is not uniformly
> distributed,) so that going "lossless" is practically speaking, a 
> meaningless
> waste of storage and processing. Some artifacts in digicam images with 
> Bayer
> mask sensors will greatly exceed jpeg2000 artifacts at reasonable 
> compression
> ratios.
>
>
<|_:-)_|>

C M I Barker
Cambridgeshire, Great Britain.

+44 (0)7092 251126
ftog at threeshoes.co.uk
http://www.threeshoes.co.uk
http://homepage.mac.com/zuiko
... a nascent photo library.


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