capture one 11, jpeg2000 lossless

philip brown

• November 11, 2018 03:39

Hello,

I read that unlike original jpg, jpg2000 supports losslesscompression.
In the export menus, C1 seems to only have the same normal-jpg settings. You can change the quality up to "100".

however, since 100 on regular jpeg is still lossy, I'm wondering if 100 on jpeg2000 is also lossy, an there's some other toggle to turn on pure lossless format?

when I export in 16bit jpeg2000, the filesize is about 10% smaller than compressed ARW, so I can believe that might be lossless.

However, when I export in 8bit.. the filesize is CRAZY small.
whereas 8bit jpg is half the size of 8bit png..
8bit jpg2000 is half the size of the jpg, or even smaller?
Can it still be lossless, taking into account the 8bit conversion??
Something seems wrong here...

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  Rob Wiejak

  • November 12, 2018 17:02

  I would approach it like this:
  
  1. save the original image as uncompressed TIFF.
  2. save the same image as lossless JPG2000
  3. in another picture editing application (i am working with affinity photo) I would put the TIFF image at the bottom layer and JPEG2000 on top layer, then select 'difference' merge mode.
  4. Merge visible to apply a filter to it
  5. Using exposer filter I would add enough exposure to see the difference (+5...+30, etc.)
  
  If there is no difference between the two images, you will see a black screen
  If on the other hand there are differences you will see them
  
  Example, original image:
  http://zabcia.ca/GFX/diff.jpg
  
  TIFF - J2K@100% + 10exp:
  http://zabcia.ca/GFX/diffj2k%2B10exp.jpg
  
  TIFF - JPG@50% + 10exp:
  http://zabcia.ca/GFX/diffjpg%2B10exp.jpg
  
  This is not scientific, but you can experiment with it and conclude what is acceptable to you.

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  Pavel Derka

  • December 17, 2018 19:47

  ^ that's a fantastic tip! Thanks.

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