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Thread: RGB to CMYK conversion problems

  1. #21

    Default Re: RGB to CMYK conversion problems

    Quote Originally Posted by kahheng
    Nic you're absolutely spot on. However, lots of mags (even those with in-house separation) here tend to want the photographer to supply CMYK tiffs. Go figure. I keep telling them that conversion to 4 colour should be done on their end for best results to no avail. Most of the time is because the separators they use do not want the hassle of having to convert the RGB files themselves - yes it is either pure laziness, or incompetence, or ignorance, or whatever to 'sub' this impt step to the image provider; and the client has a tendency to believe the separator more than the creatives since the assumption is that the separator "ought to know better because they are the separation experts" ;-)

    A very experienced di friend agrees with me that that's true of quite a lot of the clients he works with here too. Hence, a 'general purpose' CMYK file and a proof is about as good a real world way of working as can be had to suit the client's way of working. Surely I am not going to piss off the client just because I think I know better ;-)

    Even FINAL sharpening should ideally be done ONLY when the picture has been cropped to size after layout, but it's also not done this way here nearly all the time.

    There are lots of cart-before-the-horse workflows to negotiate in the real world. I wished I had more enlightened clients like yours. But it is a lot better here these days already than even just five short years ago.
    Hey kahheng,

    I totally agree with you on the part that some local mags need CMYK files from photogs, that really explains the many color shifts in publications.

    Profiles aside, I must apologise for my harsh tone in the earlier post to mattlock. *i owe you a coffee* I am really just angry with the state of the industry here. If we want to go to first class creative hub, these problems must be addressed first.

    Gamut Labs exist for a simple reason, to make workflows seamless and in tune with current technologies. Maybe you are right about me and my bunch of photog friends being lucky to have the mags doing the "aRGB+Color Proof" way but we had to educate them, slowly but surely.

    I will be really happy to form a little user group to push forward a setup of workflow guidelines we all can use here at the meantime setting up the correct workflows for design houses.

    It's time we stop bitching about it and do something about it.

    I have managed to turned a little humble printshop to a WYSIWYG bureau because I believe it can be done, RGB or CMYK, no problems.

    Let's up the standards, starting with ourselves, making sure we get our workflows color-calibrated so we can say we have done our part.

    I have pm the moderator and propose that we can do a sticky primer (to be updated whenever there is new techonology) about the various workflows so that we move forward together.

    I can't do this alone as I do have limited knowledge only. Anyone with me on this?


    Cheers,
    nic

  2. #22

    Default Re: RGB to CMYK conversion problems

    Quote Originally Posted by mattlock
    hey there,
    I'm having problems getting accurate colours when I convert RGB to CMYK in Photoshop.
    Converting from Wide Gamut RGB or Prophoto RGB to US Web-based SWOP V2 ends up with the colours looking all wrong. In Photoshop, the CMYK conversion looks ok but when I view the converted TIF file in ACDsee, the colours are nothing like the RGB version.

    I've also tried converting from sRGB to CMYK, on occasions the conversion is quite accurate bu then there are instances when the CMYK file has inaccurate colours and the highlights get badly blown out, and the dark areas become almost pure black. Generally the image turns too contrasty. Am I doing something wrong here?

    any help will be appreciated, thanks
    On reading this again, Mattlock, er, are you actually expecting CMYK conversions to mirror your original RGB files very very closely in colour when you say "..the colours are nothing like the RGB version"?

    If you were, er, I'd say that no conversions can be perfectly consistent - certain colours for instance, are absolutely impossible to translate across perfectly.

    You do need to operate in the CMYK environment or at the least, simulated CMYK environment and tweak your files all so often to get the colours and tones looking right if you have to submit CMYK only tiffs.

    Also, Photoshop isn't the best 'converter' for the job, though even separators use it so often, so blindly. There are much better custom software for the job, in truth.

  3. #23
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    Default Re: RGB to CMYK conversion problems

    Back at my office, we leave everything in the good hands of the printing company. They would provide us with a color proof, everything looks ok, we sign off, keep the extra copy and everyone goes home happy. If anything goes wrong, we only need to refer back to the proofs and we invite the printing boss for coffee. :P

    The photographers I've hired, would normally send their photos in the highest resolution possible with all the color profiles tagged. I wont ask them to convert the colors to CMYK mainly because I would need to edit them to fit into my design layout. My main prob is usually monitor color calibration over time (mainly due to stress and no time to actually calibrate). With the new Indesign CS2 I m using now, the black output is much more richer than my old and clunky QuarkExpress. I used to have many things to worry about that I didnt spend much time on my actual work, that is to plan the layouts but now, I leave all the color issues to the printers. They would offer to calibrate my monitor over time if the colors is starting to look 'weird' on their end.

    So the moral of the story is, its more than just sending your photos in the right color space. Sometimes I wish there was just one standard that we could follow so that everyone could be on the same page. But then again, there's Pantone color and wide gamut printing which always give me headaches when dealing with the printing company that cant provide almost accurate color proofs. They would always charge us extra. We are a budget concern publishing house and my boss would normally decline the extra cost. All I could do was to keep my fingers crossed and pray that the color will turn out 'all right' when the magazine hit desk.

    Anyway, dont fret too much about the CMYK thingy. Its not the end of the world. There are solutions but sometimes these solutions provided adds more cost. Normally from the printer side. The safest bet for most photographers is to work and save their files in the highest quality possible and send over to the design houses in RGB. Then the rest is up to the designers and finally the printers. Just sharing my experiences. I might be wrong but then they are experts here who can correct me.

    Cheers!
    Last edited by hazmee; 4th March 2006 at 12:57 AM.

  4. #24
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    Default Re: RGB to CMYK conversion problems

    Hi Mattlock,

    Wish this would help,

    at your photoshop/edit/colour setting../Pls check advance mode(by doing so, then only you will be able to choose these..

    then choose these..

    Working space--
    RGB: sRGB IEC61966-2.1
    CMYK: Photoshop 5 default CMYK
    Gray: Dot gain 20%
    Spot: Dot gain 20%

    Colour management policies--
    RGB: Preserved embedded profile
    CMYK: Convert to working CMYK
    Gray: Off

    Profile mismatch+ missing profile check box-- all uncheck.

    --Forget about ACD SEE to view CMYK, stick with PS
    --For printing press definitely have to change to CMYK
    --Swop coated for US will give a warm cast... not meant for this.. more for news print..

    Try it... If you see the magic, just PM me..

    I am just a printing Guy..

  5. #25
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    Default Re: RGB to CMYK conversion problems

    By doing so... you can switch mode with minimun loses..

  6. #26

    Default Re: RGB to CMYK conversion problems

    guys, thanks for the help, I really appreciate it.

    The problems started when I did my conversions using Photoshop and the CMYK image looked absolutely ok, but when I viewed the saved CMYK Tiff file in ACDSee, the colours were all messed up. These were the colours that were reproduced when I sent them in for printing at a print shop at Peace Center (they require a CMYK conversion)

    Maybe it is just an ACDSee issue but somehow it's too coincidental...

    So I started trying to figure out what was wrong with my Photoshop conversion. I ended up having to do very careful Selective Colour adjustments to the CMYK file (generally a removal of reds in the Magenta channel and yellows in the Yellow channel) just to get a fairly accurate reproduction of the sRGB version of the image. But it is very time consuming and I rather fix the source of the problem

    kahheng, when I say nothing like the RGB image, I mean that the skintones turn into garish red, greens turn neon, greys turn to black, highlights blow out totally. I'm lucky that I haven't had any magazine work turn out like that (apart from a big shoot that came out with a horrendous yellow cast throughout), but I don't want to find out for myself.

    and, yes, as much as I would love the printers to be all great at converting files to CMYK, I don't have alot of say in who does the printing sometimes. I'm especially worried about low-key, dark images. greys tend to clog up into pure blacks when they convert the files. So I'm trying to see if I can control the process abit more on my side (get an idea of what they are seeing so I can throw a curve to raise the detail in the shadows, that kind of thing)

    erizai, I really really really appreciate that. I don't get enough information on the different CMYK profiles so it's just trial and error...I'm gonna try using the info you gave me.

    Alternatively, is there any dedicated software that can do a RGB to CMYK conversion?Maybe that will be the end of my worries and I don't need to make things more complicated for myself

  7. #27

    Default Re: RGB to CMYK conversion problems

    Quote Originally Posted by mattlock
    guys, thanks for the help, I really appreciate it.

    The problems started when I did my conversions using Photoshop and the CMYK image looked absolutely ok, but when I viewed the saved CMYK Tiff file in ACDSee, the colours were all messed up. These were the colours that were reproduced when I sent them in for printing at a print shop at Peace Center (they require a CMYK conversion)

    Maybe it is just an ACDSee issue but somehow it's too coincidental...

    So I started trying to figure out what was wrong with my Photoshop conversion. I ended up having to do very careful Selective Colour adjustments to the CMYK file (generally a removal of reds in the Magenta channel and yellows in the Yellow channel) just to get a fairly accurate reproduction of the sRGB version of the image. But it is very time consuming and I rather fix the source of the problem

    kahheng, when I say nothing like the RGB image, I mean that the skintones turn into garish red, greens turn neon, greys turn to black, highlights blow out totally. I'm lucky that I haven't had any magazine work turn out like that (apart from a big shoot that came out with a horrendous yellow cast throughout), but I don't want to find out for myself.

    and, yes, as much as I would love the printers to be all great at converting files to CMYK, I don't have alot of say in who does the printing sometimes. I'm especially worried about low-key, dark images. greys tend to clog up into pure blacks when they convert the files. So I'm trying to see if I can control the process abit more on my side (get an idea of what they are seeing so I can throw a curve to raise the detail in the shadows, that kind of thing)

    erizai, I really really really appreciate that. I don't get enough information on the different CMYK profiles so it's just trial and error...I'm gonna try using the info you gave me.

    Alternatively, is there any dedicated software that can do a RGB to CMYK conversion?Maybe that will be the end of my worries and I don't need to make things more complicated for myself
    mattlock,

    there's an "early binding" technique, i.e open up file in PS, duplicate, convert to CMYK (best if you have final destination profile) then edit+save in CMYK.

    pros - if the profile is correct, no more heartaches.
    cons - you have to do a RGB version from scratch for web or RGB printing

    if that is the only way with that mag, you might wanna try that.

    "late binding" - convert after editing - is always the best to ensure maximum color info in source file.

    that was the old skool method and should save your from the messy conversions.


    cheers,
    nic

  8. #28

    Default Re: RGB to CMYK conversion problems

    Quote Originally Posted by mattlock
    guys, thanks for the help, I really appreciate it.

    The problems started when I did my conversions using Photoshop and the CMYK image looked absolutely ok, but when I viewed the saved CMYK Tiff file in ACDSee, the colours were all messed up. These were the colours that were reproduced when I sent them in for printing at a print shop at Peace Center (they require a CMYK conversion)

    Maybe it is just an ACDSee issue but somehow it's too coincidental...
    ACDsee? It doesn't translate CMYK files properly. Never has AFAIK and I have been using it since v2.x. ;-) It's pointless to view CMYK files with. Try something else like Iview Media Pro or something if you need a cataloguing app. Otherwise, just browse with Photoshop since you already have it.

    Quote Originally Posted by mattlock
    So I started trying to figure out what was wrong with my Photoshop conversion. I ended up having to do very careful Selective Colour adjustments to the CMYK file (generally a removal of reds in the Magenta channel and yellows in the Yellow channel) just to get a fairly accurate reproduction of the sRGB version of the image. But it is very time consuming and I rather fix the source of the problem
    That's just the nature of CMYK versus RGB (and why would you be working in the sRGB colour space at all? No, seriously.)

    Reds are always hard to reproduce accurately in CMYK. Period. (Er, 'pure' blues as well)

    In the ideal workflow world, the separator would use his specialist RGB-CMYK converter with a tightly tuned set of target CMYK profiles for his various inksets-paper combinations, to minimise this problem when you submit RGB-only files.

    In the non-ideal world that you live in where you are expected to do the conversion, you can do no better than to ask them for their custom CMYK profile for the press/ink/paper (if they know what they are doing, and pray they are as colour managed as you are), or just work using that profile I had mentioned, and continue to tweak.

    Time consuming? Yes, it is, since you care enough.


    Quote Originally Posted by mattlock
    kahheng, when I say nothing like the RGB image, I mean that the skintones turn into garish red, greens turn neon, greys turn to black, highlights blow out totally. I'm lucky that I haven't had any magazine work turn out like that (apart from a big shoot that came out with a horrendous yellow cast throughout), but I don't want to find out for myself.
    It's an ACDsee illusion. For a supposed Swiss Army knife of an image browser, ACDsee is surprisingly limited in this regard. Always has been as far as I can remember. Stop using it for CMYK files.

    Quote Originally Posted by mattlock
    and, yes, as much as I would love the printers to be all great at converting files to CMYK, I don't have alot of say in who does the printing sometimes. I'm especially worried about low-key, dark images. greys tend to clog up into pure blacks when they convert the files. So I'm trying to see if I can control the process abit more on my side (get an idea of what they are seeing so I can throw a curve to raise the detail in the shadows, that kind of thing)

    -snipped-

    Alternatively, is there any dedicated software that can do a RGB to CMYK conversion?Maybe that will be the end of my worries and I don't need to make things more complicated for myself
    You really need to speak with the the client, and their separator - and ask them to help you out with these types of pictures. Explain what you're trying to do. Otherwise, it's really just too bad. Just dump them the RGB file, a colour proof, and tell them to handle the conversion because you feel you're not confident enough in getting the best quality out of the conversion.

    There's no panacea for the RGB-CMYK translation problem you're facing. Having the target CMYK profile and working within its contraints is your best option if you have to submit CMYK tiffs. If the target profile is not available, I'd just go the general purpose CMYK conversion way (US Sheetfed coated - until such time it ceases to be a good general purpose profile), and submit a proof print at the same time.

    The 'better' dedicated converters are dedicated to the output devices and inksets the press itself is using.
    Last edited by kahheng; 4th March 2006 at 11:01 AM.

  9. #29

    Default Re: RGB to CMYK conversion problems

    ok, thanks for the info. down the toilet you go, ACDsee!

    out of curiosity,is there a good guideline for the values of the black points and white points for CMYK files that I can safely follow to prevent clipping, while maintaining a decent contrast, when printed in CMYK?
    Last edited by mattlock; 4th March 2006 at 11:00 AM.

  10. #30

    Default Re: RGB to CMYK conversion problems

    Its not just local mags that ask for CMYK...I've done images for a few international ones that want CMYK as well...so much so that I would rather work in the limited colour space of CMYK than have head/heartache later on...but for images with alot of difficult colours like light purple and yellowish green or BW images, still have to use RGB...and sRGB to be safe...

    and some "pro" local printers don't even have calibrated monitors...went to one once asking to tweek some colours on the spot and they told me that their monitors not calibrated and assured me the colours would be good...not...

    Oh yeah, agree with the others...send colour proofs...I usually send one A4 and the rest 2 to an A4 (A5)...
    Last edited by theRBK; 7th March 2006 at 04:26 PM.

  11. #31

    Default Re: RGB to CMYK conversion problems

    same here, i colorproof with epson2100 (which matches to my screen.)

    I send a A4 for every image i give to the magazine.

    i use the 'late binding' approach.


    Gamut Labs, I think i need a new profile for my paper, it's running a little. can you do it? PM me.

  12. #32

    Default Re: RGB to CMYK conversion problems

    Quote Originally Posted by anka
    same here, i colorproof with epson2100 (which matches to my screen.)

    I send a A4 for every image i give to the magazine.

    i use the 'late binding' approach.


    Gamut Labs, I think i need a new profile for my paper, it's running a little. can you do it? PM me.

    Been out of the radar for awhile, just settling down in London and using dialup till my broadband is up next monday!

    My very first post recommended a color proof everytime since most people do a "late-binding" method.

    anka - will pm you, but i will only be back on april 3rd.

    cheers,
    nic

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