The problem here is that the cmyk image already has a decoloration when I bring the .PDF into photoshop no matter what profiles I use there is still that basterding color shift. On 12 Feb 2016 15:50, "Jason S" <jasonsta...@gmail.com> wrote:
> I found out when wanting to copy the lightness channel from the CMYK image > converted to lab to paste it in an RGB ver, and saw that just converting > all of it from there to RGB seemed to do the trick. > > Maybe because as lab works with a lightness channel, it doesnt need to do > any specific curve manipulations to recreate levels in another space > but go figure. > > nevertheless, hope that can work! > J > > On 02/12/16 10:13, Jason S wrote: > > You can have CMYK images in 16 or 32 too, but if your sources are 8 bit, > it can be fine if there aren't too wide gradients or making wild corrects. > > But here's what seems to work, > > converting from CMYK -> Lab Color seems to keep all levels as they were, > and then from Lab Color -> to RGB ... also seems to keep all levels as > they were! > > (It might be best to convert to 16bit (if they were in 8) before doing so.) > > Cheers, > J > > On 02/12/16 10:08, Sebastien Sterling wrote: > > I think it has to do with RGB being additive; adding all colors leads to > white > > and CMYK being subtractive. adding all colors leads to black > > RGB has so many more colors, it must be like clamping the bit depth but > not quite. > > at any rate you loose something going one way, so it is a destructive > workflow. > > On 12 February 2016 at 14:55, Jason S <jasonsta...@gmail.com> wrote: > >> It weird because if you take screenshot while in CMYK colorspace and >> paste in an RGB image, >> there you go, same blacklevels and everything as in CMYK but in RGB space. >> >> So would there be a way to "bake" color info from one colorspace to >> another? >> (assuming it's for hirez images, otherwise you could just take >> screenshots :P ) >> >> I find it surprising that something like photoshop cant manage to make a >> 1:1 conversion. >> >> >> On 02/11/16 18:19, Sebastien Sterling wrote: >> >> Have been doing variants of this, to no great success, it doesn't seem to >> want to change anything, haven't tried absolute colometric though, maybe i >> will try that. The Web converter actually does have an effect, but not >> perfect, it does bring the ultramarines back towards black. >> >> On 11 February 2016 at 23:02, Sven Constable <sixsi_l...@imagefront.de> >> wrote: >> >>> Photoshop Edit->Convert To Profile >>> >>> You will see the source color space embedded in the original (if there >>> is any) and the target color space. >>> >>> Choose one of the RGB spaces (eg. sRGB). >>> >>> Check blackpoint compensation and Relative Colometric. >>> >>> Tick Preview to see the result. >>> >>> Ideally you should see no to minimal color shifting, but this depends on >>> the original color profile within the CMYK file. >>> >>> >>> >>> I'm pretty sure this what you'll get with that web based converter. >>> >>> However, your problem is not to get a close color match but to change >>> colors (ultramarine blue to black). Not sure if this is possible without >>> manual grading but you can try *unchecking black point compensation* >>> and switch to *Absolute Colometric*. Then switch through the different >>> color profiles and see if any of it will change the ultramarine blue back >>> to black. >>> >>> If this worked somehow, do a second conversion to sRGB *with blackpoint >>> compensation ON and relative colometric*. >>> >>> >>> >>> If this won't work, I think there is only manual color grading or have >>> the client send you "correct" files. >>> >>> >>> >>> sven >>> >>> >>> >>> >>> >> >> > > >
