Convert to CMYK

Discussion in 'Digital Discussion & Q&A' started by lunes, Apr 10, 2017.

  1. lunes

    lunes TPF Noob!

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    Hello, i have a picture that i will send to a press to get printed, but the press want the picture to be in CMYK and 300dpi minimum.

    How do i convert this file/picture to cmyk and how do i check how many dpi it have?

    The picture is now in sRGB and 3072x3072 px.


     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    What software do you have?
     
  3. Ysarex

    Ysarex Been spending a lot of time on here!

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    What you're being asked to do is inappropriate -- it's incorrect procedure in the processing sequence to print your image. The people at the press should know this. If they don't that's a problem. If they do and they're asking anyway that's a problem.

    Joe
     
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  4. KmH

    KmH In memoriam Supporting Member

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    Is this in regards to a photo contest?
    Or the better question is - How is the print going to be used?

    Digital photo print resolution is ppi - pixels per inch.
    The print resolution determines the print size.
    3072 x 3072 is the image resolution.

    An EXIF reader will show what ppi the photo has assigned to it now, and most decent image editing applications can be used to change the ppi to whatever value is appropriate for the print size.

    Like Joe says, it's odd the printer is saying you have to handle setting the color space and the print resolution.
    The printer should be able to set the print resolution (ppi) to the appropriate value with software they have.
    The printer should also be able to change the color space from sRGB to CMYK.

    In other words the print resolution is not fixed until a digital photo is printed and can be changed before printing.

    Here's the basic math.
    3072 pixels divided by 100 ppi = 30.72 inches
    3072 pixels divided by 200 ppi = 15.36 inches

    So as the pixels per inch value increases the print gets smaller.

    By the way - Press printers usually concern themselves with lpi - lines per inch.
    Dpi - dots per inch - is a resolution value of inkjet printer machines. It takes many dots to print 1 pixel.
     
  5. lunes

    lunes TPF Noob!

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    It's actually not the press itself which i will send the file to, but to a intermediator, which is a site you can buy stickers from..

    My stickers will be in 10x10cm, the site says: "designs must be set to the correct dimensions and of 300dpi or more and in CMYK"

    I found this site: Online RGB to CMYK conversion Will it do the job?
     
  6. Ysarex

    Ysarex Been spending a lot of time on here!

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    OK, so I'm going to assume you're dealing with a cut-rate and cut-corners business. The site you found online to do the conversion will work. BUT it also illustrates what's at issue here. To use that site you are given two options to select a CMYK profile to handle the conversion. You can either 1. chose a generic profile from a drop box or 2. upload the profile for your press. The correct procedure is to upload the profile for your press. The option to chose a generic profile is provided for people who can't do the job correctly but still want to do the job.

    The job of CMYK conversion, requiring a press specific profile, is the responsibility of a respectable press operator. That's why I first responded that the request to you to do that job was inappropriate. I'm going to assume you don't have that press specific profile. The result of not doing the job correctly is typically a noticeable variation in color and tone between the original and the press output.

    Joe
     
  7. lunes

    lunes TPF Noob!

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    I have encountered some problems..

    I take it from the beggining, i made an image on my ipad (in sRGB) which i converted with rgb2cmyk.org

    When i open the picture in "photoshop fix" i can see what kind of colour it has and which file type, but for some reason the file type and colour seem to have change back to sRGB, and for some pictures (i made a few converts with both different and same profiles) it don't show which colour type it has, it only shows the size (as PX x PX dimension)

    So i sent the file through my email and open it on my desktop, with the picture on my desktop i open the tab "characteristics" to watch the colour-scheme. It had 72dpi and was in sRGB!

    So i tried to convert the files (i also sent the original file in sRGB to my desktop), through rgb2cmyk with my desktop, but it didn't change anything.

    So i start to explore rgb2cmyk.org, and tried their PDF-format conversion, which says it automatically makes the picture to 300dpi.

    So i took the file (.jpeg) searched up a site to convert it from .jpg to PDF, when done with that convertion, i convert it on rgb2cmyk from rgb to cmyk, and it worked out.

    So i open the file, open the characterisrics >information checked the "colour presentation". It says 300dpi, but nothing on "colour presentation", simply empty..

    I try to explore more and open the "print out" window instead, under "alternative" i found "colour management", opened it up and came to different profiles.. Under "advanced" there was something called "unit profile", which was set on "system standard sRGB (with a code behind). All the options contained different codes with sRGB, except one which was called "Agfa : Swop Standard", so i changed to that one.

    When done, the picture basically turned black and white. I tried the same settings on the other files, which i never converted to pdf, to and the same happen there..

    I also changed "profile for impressions conditions", which where right below "unit profile", and set it from "system standard (WCS-profile for sRGB- impressions conditions)" to "WCS-profile for ICC-impressions conditions)", but it didn't changed the colours of the picture.

    Right now i'm pretty tired of this, and i don't know much about what i'm really doing.

    When i convert through rgb2cmyk, it changed the tone of the colours, and maked some colours more dark, not any radical changes..

    What should i do? I don't want to risk the image to be printed black and white. How should i convert this image to 300 dpi (which i guess i already done) and in cmyk, and be sure that it really is 300dpi and cmyk?

    How can i make sure that there won't be any risk for radical changes on the finish output?
     
    Last edited: Apr 11, 2017
  8. Ysarex

    Ysarex Been spending a lot of time on here!

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    You can't. You shouldn't be doing this in the first place and the reason is because you can't do anything to make sure there won't be a risk for radical changes on the finished output. That's why this is not your job to do; it should be done by the press operator. The fact that you've been instructed to do something you shouldn't do says volumes about the business you're dealing with. Proceed at your own risk and my advice would be to expect to live with what you get.

    Joe
     

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