Re: [Gimp-user] image work

[Pat David <patdavid gmail com>]

If you’re not calibrating your monitor and proofing with profiles from your
printer you’re likely facing a long, painful road to “good” results...

If you want accurate colors, calibrate, profile, proof.


On Sun, Jul 12, 2020 at 5:48 AM JLuc <jluc no-log org> wrote:

> Hello
>
> I'm using gimp and scribus to produce CMYK PDF
> and i have issue with the photograph rendering of the printed books or
> magazines.
>
> The original image files come from various cameras or smartphones
> and lots of différente photographers, none of them being professionnal.
> They all are RGB and many of them are not technicaly perfect
> but at least i manage to get high-enough resolution pictures.
> The issue is with colour rendering :
> many of them are printed too dark,
> and the dark parts are over-dark, flattened and with no details.
>
> AFAICT my scribus settings for colour management are OK (ICC profile...).
> I havent a calibrated monitor.
> What is see on screen is very nice - or at least nice enough -
> Only printing is the issue.
> The industrial printer i send my PDFs to prints on offset paper
> - which i was told adds 2 or 3% to the red channel.
> When i print localy on my deskjet printer, i kindof reproduces the "too
> dark" effect,
> which can help me "debug" and improve the rendering.
>
> When scribus displays the "out of gamut" areas, i see that much of these
> pictures are out of gamut.
> Bringing these picture more "in gamut" could help.
> How can i achieve this ?
>
> EG this public domain picture https://pxhere.com/en/photo/1575227
> This one is not dark overall compared to others.
> I can see the tomatoe are a bit dark but overall the picture looks bright
> and balanced enough,
> or at least there is a clear color contrast between tomato and salad
> colors.
> Dont you think so ?
> When printed, both the salad and the tomato looks much darker
> and there is no more contrast betwen tomato and salad.
> I tried editing this photograph with gimp so as to improve print :
> - selected tomato red area with progressive selection, boosted the red and
> calmed down the blue and green
> - selected the salad green area with progressive selection and added some
> saturate effect
> On screen the result is better, brighter.
> But when printed, it is only very slightly (allmost not) improved.
>
> Another example picture is here :
> https://pic.infini.fr/40kyb5S0/L6oygOf7.jpg
> This is not so good a picture.
> It's been edited a bit but that's not enough.
> The dark part (door and water) are dark but we can see details in them on
> screen.
> When printed, these dark parts look flat dark brown-black with no details
> at all.
>
> How can i improve that ?
>
> JLuc
>
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