DNG use a JPEG loss-less compression, supporting 16 bits color depth.
It's an improvement of JPEG algorithm done by Adobe.
http://en.wikipedia.org/wiki/Digital_Negative_%28file_format%29DNG store RAW data, not demosaiced, from your bayet filter sensor :
http://en.wikipedia.org/wiki/Bayer_filterPNG (or TIFF), store demosaiced image data, which take more size.
http://en.wikipedia.org/wiki/DemosaicingPNG use LZW like compression for image data. It's loss-less too, but
compression ratio is not the same than JPEG lossless, or better than
Wavelets (JPEG2000 or PGF)
Gilles Caulier
2010/10/20 Josh Jones <
[hidden email]>:
> Hello,
> I am using Digikam 1.5 with Kubuntu 10.10. I shoot and import into
> Digikam with DNG and save as PNG when using the image editor. My
> question is why do I get such a large PNG file after performing very
> small changes (levels, etc) to the images? For example, I started out
> with a 10.7MB DNG file, adjusted the level, saved file as PNG with level
> 9 compression, and received a 45.7MB file. Both are 16bpp, and I just
> can't figure out where all the extra comes from. Any thoughts?
> Thanks
> _______________________________________________
> Digikam-users mailing list
>
[hidden email]
>
https://mail.kde.org/mailman/listinfo/digikam-users>
_______________________________________________
Digikam-users mailing list
[hidden email]
https://mail.kde.org/mailman/listinfo/digikam-users
Locked
