Re: Lighten dark colors

Le 10/07/2020 à 12:00, Bert Driehuis a écrit :
> If your printer is an offset outfit, chances are they are using
> Fogra39. 

Yes they are !
I could talk to a pre-press person and learned that the ICC is Fogra39.

He said that "Offset paper increases red chanel by 2 or 3%".
That could contribute to darkening effect.

> You probably don't have a cheap way to do a trial print, do you ?

Printer proposes Cromalin or Chrome-alun.
It's 200km away... So maybe i'll go there and also have a splash in the closeby mediterranee.

> Don't know an answer to your question, but using ImgeMagick to fix up
> jpg colors will significantly reduce image qsuchuality, 

Ah :-/
What sort of quality is reduced with ImageMagick ?
Even with that quality loss, maybe lessening that bad "dark area flattening and darkening" effect
would be worth some imagemagick quality loss ?
I could apply it selectively.

 > so figuring out the ICC profile is your best bet.

Until now i used "ISO Coated V2 300%" becauses this was the ICC for the previous printer.
Now i'll switch to FOGRA.
But even before, I didnt achieve perfect photo rendering except on specific photos.


JL


> On Fri, Jul 10, 2020 at 10:09 AM JLuc <[email protected]> wrote:
>>
>> Le 10/07/2020 à 09:56, JLuc a écrit :
>>> My new printer didnt provide an ICC profile file when asked (said it's not required afaicr).
>>>
>>> Printed photos are not too bad but are quite often too contrasted
>>> and dark areas appear flattened and shifted to the very dark.
>>> Sometimes also the light areas appear also flattened and shifted to the very light
>>> but most issues are with darker areas.
>>>
>>> I've asked some advices to the printer but i'm afraid i wont get usefull answer.
>>> (Do you sometime get any usefull answers from your printers ?)
>>>
>>> As for now i'm thinking of bash-editing all images so as to curve the dark colors lighter.
>>> How could i best bash achieve this on linux ?
>>
>> After trying a few parameters it looks like this command could do :
>> convert cheval.jpg -level -0%,100%,1.5 cheval-level0,100,1.5.jpg
>> My other questions remain open.
>>
>>> What should i care do to avoid worsening the print ?
>>
>> JL
>>
>>
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