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Best way to convert RGB < CMYK?

Jan 2, 2013 11:49 PM

Tags: #photoshop #help #color #cmyk #rgb #printing #color_management #print #convert #convert_color #ps6 #web_to_print #convert_rgb_to_cmyk #rgb_cmyk #print_cmyk

Hello Everyone ...                                                                                                Level: Newbie  OS: Win7 64bit  Ps: Cs6

 

 

 

I have made a few QR Codes using a generator and a URL shortener and then I used Photoshop to add Actions and some Styles.

 

The person for whom I made them initially only wanted them for his website so I made them in RGB and saved them for the web in 24 .png. However, he liked them so much he asked if I could send him the images in a file in which he can print them.

 

Now, from what I understand ... (what little I understand of Ps and graphics etc. at this point), I should send him the images in the .eps format ~ which is Best for printing~??

 

I've just read a lot of different information about converting from RGB to CMYK and so now I am hoping someone can help me outta the crazy maze my mind has found itself in

 

Should I Flatten the layers in my image? Or should I simply Merge the layers?

 

If I understand correctly I should not use the: Image > Mode  but rather, I should use the Edit > Convert to Profile ... or, is this really Only for Photographs?

 

What is meant by Target Space? Does this refer to rather the image is RGB, sRGB or CMKY?

 

Any tips for when I should and/or shouldn't check the options in the Convert to Profile dialog box?

 

I read this: go to > Edit > Convert to Profile and once there select your target profile ( a copy of which should be in the [your computer] > Library > ColorSync > Profiles folder, or else it won't appear in the pulldown menu.

 

Um. What? (lol)

 

A Copy of what? My image? A Target Profile? A Target Space?

 

any way, moving along ...

 

Am I making this too complicated?

 

In your opinion and by your experience what would be the best way to get the best printing results? Meaning, how can I get the colors to look the same or as close to the colors of the image that displays on the web?

 

If you need me to post the image just let me know.

 

Sorry for the wicked long post. I appreciate your time and efforts w/all my <3

 

Thanx!!

 

PS. I just did a Preview of my image with the Convert to Profile and the background color (which is: c6fbd9) of the image becomes rather dull. So, all in all there must be a way for people that work with computers to generate images that are as colorful as they appear on their sreens. Right?

 
Replies
  • Currently Being Moderated
    Jan 3, 2013 3:45 AM   in reply to Kar209

    Now, from what I understand ... (what little I understand of Ps and graphics etc. at this point), I should send him the images in the .eps format

    No.

     

    A Copy of what? My image? A Target Profile? A Target Space?

    The icc-profile representing the target space.

     

    What is meant by Target Space? Does this refer to rather the image is RGB, sRGB or CMKY?

    The target space is the one into which the image is to be converted.

    In your case this would be the required CMYK space – if you have that information.

     

    Am I making this too complicated?

    Yes and no.

    First it can be OK to pass on RGB files and let the person/s who know what the target space actually is handle the separation if you have not been given specific requirements. But the appearance of the image may change in separation.

    Secondly you may want to read up on Color Management and printing.

     

    So, all in all there must be a way for people that work with computers to generate images that are as colorful as they appear on their sreens.

    If you work in a larger Color Space and have to output the image in a smaller one a trade-off is necessary.

    Many/most RGB spaces contain colors that are simply out of gamut for many/most CMYK spaces.

    One has to live with that and just try to get an acceptable result.

     
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  • Currently Being Moderated
    Jan 3, 2013 4:00 AM   in reply to Kar209

    In your opinion and by your experience what would be the best way to get the best printing results? Meaning, how can I get the colors to look the same or as close to the colors of the image that displays on the web?

    How an image appears »on the web« may be a more vague description than you appreciate.

    You can work in srgb and embed the color space, but what if the the image is viewed with a non color managed browser?

    And what about the screens it is being displayed on? They may have vastly different gamuts and may or may not be regularly calibrated/profiled.

    And if you consider tablets, mobile phones etc. there is no color management to begin with (at current).

     

    he asked if I could send him the images in a file in which he can print them.

    Did your client mention which print process they intend to use?

    Are they printing as in »print on a desktop printer« or »offset/gravure/flexo/… print« or something else?

     

    Any tips for when I should and/or shouldn't check the options in the Convert to Profile dialog box?

    Have you read what the Reference/Help have to state about those settings yet?

    In any case: The »Intent« can make a considerable difference, but with photographic images the decision is usually between Perceptual and Relative Colorimetric. With graphic elements Saturation might also be worth checking out. (edited)

     
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  • Currently Being Moderated
    Jan 3, 2013 4:26 PM   in reply to Kar209

    First, you don't need to convert the file from RGB to CMYK in order to print if the person is using it for in-house printing on inkjet printers or office laser printers etc. The only time you need to convert a file to CMYK for printing is if you are sending it out to a commercial printer that uses plate printing. And if you or the client doesn't know what that means, then it really means you don't need CMYK.

     

    All of the office and home office printers we use can print RGB files. I know this can be confusing, especially since if you look at the ink set, it's clearly C (cyan) Y (yellow) M (magenta) and K (black), with many printers having variations in between, like light cyan, light black etc. But all of these printers take your file, whether it be CMYK or RGB, and they interpret it and output it CMYK on the fly, so you don't need to think about it.

     

    Commercial printers that use plate printing, whether it be digital plates or the old fashion aluminum plates, they have to separate the colors to CMYK, and the paper is passed through four plate presses, one for each color. So then the color has to be physically separated to make the plates. But for most printing that's old school and you don't need to think about. One example of when you might need to do that would be if you're creating packaging, or a brochure that will be sent to a printer.

     

    If you want to convert a file to CMYK, the best thing to do is go to edit ->convert to profile. Don't use assign profile, as it can change your colors.

     

    The target space is the color space you want to convert TO. So if you convert from RGB to CMYK, then CMYK is your target space.

     

    An ICC profile describes the colors in your file. This too can be confusing because you have printer profiles and paper profiles (output profiles), and you also have ICC profiles for the file (input profiles). You're concerned with the ICC profile of the file, or embedded in the file. Think of the ICC profile as a color map. It maps the mathematical value of the colors in your file to a chart that tells the output device what the values are. That's how these new printers can print without needing you to convert a file to CMYK. It takes the color mapping of your file and maps it to the color mapping of it's Ink output, so that ICC profile tells it how to translate the color in the file to the colors of its ink.

     

    That's the quick and easy explanation. This is a topic though that's covered in books and wiki articles, so if you want further explanation a quick online search will provide you with days of reading.

     
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  • Currently Being Moderated
    Jan 3, 2013 11:45 PM   in reply to Kar209

    Thought I had read that format is used for printing ... ??

    tif or psd are just fine when used in most layout applications.

    And if one provides the final data for print (meaning in the right dimensions, with all graphic elements etc.) then nowadays pdf is the preferred format.

    Also I think one should not use destructive compression (jpg for example) until producing the final document for print; because if an image will be used by someone down the line in a layout application and the final output file created from there this would likely cause additional image degredation (in most cases it may be imperceptible, but nonetheless).

     

    I need to look up what icc-profile means.

    Bellevue scott explained already, but let me add:

    One can think of the profile as the scale on a map; a distance of 7 means something diferent if you are talking miles or km. Without the scale one can determine that one distance is longer than another, but what it is exactly is not clear.

    And with an unprofiles RGB-file one could  determine that one pixel is darker, more red, … than another but not what exact color it is supposed to represent.

    The icc-profile is used to assign a color appearance to the various values in an image.

    This is done by connecting the various points in the Color Space to corresponding positions in the Profile Connection Space (PCS) which represents the totality of humanely perceptible colors (basically the Lab-space).

    CMYK-profiles also contain information on the allowed Total Area Coverage (how much ink may be printed on any point in total), how gray will be mixed from the four colours (Gray Component Replacement (GCR) etc.), the paper color …

     
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  • Currently Being Moderated
    Jan 17, 2013 11:35 PM   in reply to Kar209

    Well, you’ve certainly been generous with the Helpful-rankings … and it is a credit to you that you got back to the thread and posted your findings so that others may profit from them.

     
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  • Currently Being Moderated
    Jan 18, 2013 1:48 AM   in reply to Kar209

    I think that perhaps you are overanalyzing the problem.  First of all, it is pretty safe to say that the images that you provided to your customer aren't color managed.  That is fine for web use since most browsers are not color managed either, nor do most people have monitors that are color calibrated. Additionally, most computer monitors are only capable of displaying a small range of colors (known as a color gamut). This means that the colors you saw on you monitor won't be quite the same as what your customer sees nor what anybody else sees when viewing his web page.  Imagine going into a store like Best Buy and seeing all the TV's showing the same thing, but the color looks a bit different on every one.  You probably would like the printed results to look like what you see on your monitor.  The bad news is that with a color managed workflow, it may be close, but it won't be quite the same.

     

    Probably the best course of action (without spending the time needed to learn about color management and the money needed to get a calibrator) is to just use sRGB as the color profile of the image and Absolute Colorimetric as the rendering intent when you create the print file.  More important than the color is the image resolution.  Given that the images were created to be displayed on a web page, they are probably fairly small in height and width pixel dimensions.  For printing, it is important to consider the number of image pixels per inch.  Since you would like each of the QR matrix dots to be clear and sharp without fuzzy edges, I think that something in the neighborhood of 300 pixels per inch or better is desirable for printing QR codes.  This means that your images will print too small unless your original images were much larger than the ones that you delivered to your customer.  Upsizing an image is fraught with perils, but you might want to try "Nearest Neighbor" for resampling in order to maintain hard edges.  For better quality, you might need to recreate the images in a larger size.

     

    It appears that from what you have posted that this will be printed on a desktop printer, but even if it isn't, RGB color mode is most likely what you want.  Even if you were to convert the image to CMYK, the computer would automatically convert it back to RGB before sending t to the printer because that is the way that the computer to printer interface works.  After the printer gets the RGB file, its built-in processor converts it to the necessary CMYK or CMYKGR format that it needs to send commands to the printhead.  The reason things are done this way is that every printer is different when it comes to ink colors, ink formulation and paper interaction, how the ink is laid on the paper, how PPI (pixels per inch) gets converted to ink dots per inch, range (gamut) of colors that can be printed compared to what was sent to the printer, and on and on.  Also, things are different depending on whether Photoshop manages the colors or the printer does.  Given that your Photoshop editing environment is not color managed, you may as well let the printer manage the colors [to the limited extent that it can].

     

    The only time that you might need to convert the image to CMYK would be if you need to view color separations for an offset printing process.  It would be best to speak directly to the print service provider to get their requirements.  From my experience, an RGB file is probably still what they need, but it probably ought to have sRGB assigned (assigning a profile is different than converting), but it depends on whether you have color management turned on or off in Photoshop.  (It will probably be obvious if you do the wrong thing because the colors will be way out of whack.  In that case, undo what you did and get them back in whack.)  Unfortunately, some print service providers still don't know anything about color management and wind up mostly flying by the seat of their pants when setting up color adjustment on their printers.

     

    Regarding file format, I would suggest using any non-lossy format which means do not use JPG or PNG.  I would probably use TIF or PDF.  Ideally, the files should have originally been created as PDF vector images so that they would have been scalable.  I do not see a reason to use Encapsulated Postscript (EPS) unless required.

     
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