[digiKam] -- extracting jpegs from RAW

[Remco Viëtor]

On mardi 20 février 2018 18:22:32 CET Tac Tacelosky wrote:
> I'm a bit confused about something, and hoping someone can help.
> 
> I read that saving RAW+Fine in the camera was a waste of space, because the
> JPEG image is stored as a preview in the RAW file itself.

A jpeg preview is usually stored in the Raw, but at a much smaller size, like 
1/4 of the full size. Those jpegs are rendered with the same settings as for a 
camera-generated full jpeg apart from the demosaicing, so they should look 
identical on screen.

> But I also read that the JPEG rendering in my Fuji x100 is quite good, and
> is often better than "Save as JPEG" image I get when simply adding RAW
> images to a queue as saving them as JPEGs in another folder.
> 
> So I'm either doing something wrong, or misunderstanding something.
> 
> I don't care much about the disk space, but it's a bit of a pain to have 2
> images, displayed identically (the jpeg and the embedded jpeg preview) when
> using digiKam to rate my images after import, when I'm trying to decide
> what should happen next for each one.
> 
> And certainly I don't want to archive both the raw and jpeg if the jpeg is
> indeed embedded in the file.
 see above.

> So the question is, can I extract the camera-rendered JPEG using DigiKam,
> and would it be any different than storing the RAW+Fine or Raw+Normal?  Or
> does digiKam render it's own JPEG file from the raw, based on the camera
> settings (e..g while balance, constrast).
As explained above, the difference between the embedded and the separate camera 
jpegs is the size/resolution.
Digikam only renders a jpeg when you ask it to, using the editor. And in 
practice it's very difficult to get output from a given raw file  that's 
identical to the corresponding camera jpeg.

> Should I be saving RAW+(Fine|Normal), or is that duplicating data I can
> easily get.

If you mean "should I be saving Raw + fine to get the proper preview in 
Digikam", the answer is "no", if you want to have a full format jpeg without 
doing the editing yourself, the answer is yes (but if you don't want to edit 
the raws yourself, why do you shoot Raw as well?).

Remco