[Digikam-users] jpeg compression

[Liquiddoom]

Actually, I believe it is the other way around. PNG destroys EXIF metadata,
while TIFF keeps it intact. As for which to use, it really depends. I tend
to use TIFF because it can support other color spaces and greater bit depth
(as I shoot RAW).

On 6/28/07, Bjørn Kvisli <bjorn.kvisli at tele2.no> wrote:
>
> Torsdag 28 juni 2007 23:09, skrev Jakob Østergaard:
> > On Thursday 28 June 2007 18:20:43 Daniel Bauer wrote:
> > > On Donnerstag, 28. Juni 2007, Bjørn Kvisli wrote:
> > > > If I understand this right, assuming that the Kodac C340 uses jpeg
> > > > quality of 70 internally, it makes no sense to set a higher value in
> > > > Digikam?
> > >
> > > it still makes sense, because every new save looses some more
> > > information. Although its not that dramatic in reality, you could
> think
> > > of percents just to better understand: then if you save the 70% with
> 100%
> > > you get 70% again, if you save it with 70% you get only 49% (70% of
> 70%)
> > > and so on.
> > >
> > > I found that a jpg value of 88 in digiKam gives approx. same results
> as
> > > 80 in photoshop (in quality and size). That's the value I use for my
> web
> > > pics.
> > >
> > > However, as long as you work with the pictures better use a lossless
> file
> > > format and only save the final pictures to .jpg (if at all). And leave
> > > the originals untouched.
> >
> > A tip;
> >
> > When order paper photos from my digital images at the local shop (which
> > uses a Fujicolor service which means the actual paper photos get
> developed
> > somewhere in germany then shipped back to .dk so I can pick them up at
> the
> > local shop), I found that JPEG images are a lot better than uncompressed
> > TIFF.
> >
> > It turns out, that if I deliver TIFFs, the "clever" kiosk system will
> > convert them (most likely to JPEG) with a pretty heavy compression. If I
> > deliver JPEGs (at 95% quality) the images are not further compressed,
> and
> > they look crisp and sharp on paper.
> >
> > I tried a test run with several different pictures, two copies of each
> > picture (one JPEG one TIFF), and the TIFFs were very noticeably
> "smudged"
> > or "blurred", suffering the artifacts of a heavy JPEG compression (or
> other
> > compression that cuts out high frequencies).
> >
> > That's one case where I've found JPEGs to be superior to TIFFs, although
> > not for the reasons one would usually expect  ;)
>
>
> Interesting! I'll probably do as you in the futures. keep my images in a
> lossless format and convert to jpg before sending them off to the print
> shop.
>
> Now, I've heard about two lossless formats here on the mailing list: tiff
> and
> png. Which one is bes to use with Digikam? It seems like you keep all the
> exif data with png, but lose them with tiff.
> -Bjørn
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