[Digikam-users] Re: need advice re: format conversion

[Remco Viëtor]

on Monday 24 January 2011, Tom Cloyd wrote: 
(...)
> 
> My current revised archival storage plan is therefore -
> 
> CRW originals: store as such until 1.7.0 is readily available (no 
> problem), then convert to DNG if file size is tolerable. Otherwise, 
> convert to lossless PGF (which, I'm currently assuming, would be smaller).

I think you are missing an important difference between CRW/DNG and PGF/JPG 
here: CRW, DNG and other raw formats store the information as captured by your 
camera. To store an image as PGF or JPG, there are a few processing steps, 
that can be done in different ways (too long to discuss here, see for instance 
http://www.cambridgeincolour.com/tutorials/RAW-file-format.htm).

Short answer: keep your raw files (CRW or other), or perhaps convert to DNG. 
DO NOT store them only as PGF or (worse) JPG.

And wrt. size: PGF or PNG will be BIGGER than your raw files in most cases:
raw files store 12 or 14 bits/pixel, PGF/PNG will store 24 or 48 bits/pixel.

> JPG originals: store as such, period.
agreed, not much else you can do. 
Also, avoid repeated edit-> store cycles with JPG, if you have to edit them, 
store the edited copy as PNG or PGF, to avoid cumulative quality loss.

> 
> All originals: convert to lossless PGF for software processing, then JPG 
> for web use, retaining PGF for archival storage of processed image, if 
> desired.

See above about RAW/DNG. When I process a raw file, I usually store the result 
in PNG format (another lossless format, more commonly understood than PGF). 
Then, if I need an image for display, or printing, I convert to JPG.

> (...)

Hope this helps to clarify a few points

Remco