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I want to create a duplex printing which the back label need to be save as C1, M1, Y1, K1 channel (multichannel). The question is why did the image color shift to be more reddish look when saved as Photoshop DCS 2.0?

NORMAL PSD FILE

DCS 2.0

These are my steps in creating the multichannel:

  • I copy the Cyan channel, then I go to new spot channel on the dropdown menu, rename the channel as C1, edit the color to Cyan 100%, then paste it on the new spot channel. Then I repeat the same step to the remaining M,Y & K channels.

I really appreciate your wide explaination. There's so many usefull information i get..tq so much :)

But if it because of the color profile would this explain the reason of color shifting?

enter image description here

This is the screenshot of PSD different.left (normal psd), right (psd dcs 2.0) enter image description here

Then i tried place this two in Adobe illustrator. The color likely have no different. enter image description here

and this is when i rip the file onto HP Smartstream L&P Print Server 5.2 enter image description here

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  • The final result of a multichannel image responds to the channels order, which will be the printing order. For a better answer it might be interesting to see a capture of the image with the Channels Panel visible.
    – user120647
    Aug 23, 2018 at 7:11
  • See the answer update after your question editing
    – user120647
    Aug 23, 2018 at 10:22
  • My question is, why do you need to make a CMYK DCS when CMYK is already a valid print format?
    – user120647
    Aug 23, 2018 at 12:14
  • It is for the method of printing called "sandwich printing" for HP Digital machine. The printing material is transparent. and there was a white ink in between the front & back label..so that it was called sandwich. So here we need to separate the channel for front label & back label. I didn't really understands the reason.but it was the the machine requirement to read the color channel..
    – dayah_ML_malaysia
    Aug 24, 2018 at 5:12

2 Answers 2

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If you need to create a file in CMYK, but where the channels have been renamed to C1, M1, Y1 and K1 you only need to convert from CMYK to Multichannel and rename the channels. No need to make a new spot channel for each CMYK channel and copy the original channel, since they are already spot channels.

(I don't understand exactly why you need to do this, but there are of course many different workflows around the world.)

Now, why does the colors change when you convert from CMYK to Multichannel? This is an important question and a huge subject. I will just scratch the surface.

Basically a CMYK image is just a collection pixels which each have a set of CMYK percentages. Due to an array of physical reasons a certain CMYK color will look different depending on which device you print it on and which paper you choose (among other things). The CMYK percentages are in reality technical instructions to the printing device on which physical raster percentage to use and can't be seen as an objective way to define a color. There is no 100% reliable mathematical way to convert from RGB to CMYK.

The solution to this mess is to use a CMYK color profile which is made by measuring testprints made by a device which complies to a specific standard.

The idea is that if

  • your print shop complies to a standard (by certificate or practice),
  • you have a good calibrated screen which is in a room with the recommended lighting,
  • you convert your RGB images to the appropriate CMYK profile provided by the print shop,

you will get the best possible preview on screen of how the colors will look like on print.

CMYK images can be untagged, without color profile, but there is no way to convert an RGB image to CMYK without using a color profile. When you created the initial CMYK image you have (consciously or not) chosen a specific CMYK color profile. If you just choose Image > Mode > CMYK Color, Photoshop will use the color profile specified in Edit > Color Settings... > Working Spaces > CMYK. This profile is also referred to as Working CMYK.

The colors you see on your screen is how your CMYK image would look if it was printed by a print shop which complies to the CMYK color profile of the image. If the image is untagged it will be shown as if it were Working CMYK. There is no way to see it "without color profile".

Multichannel mode doesn't use color profiles. I believe it is mostly meant for spot colors. The colors you see on screen is Adobe's best bet on how the spot colors will look on print based on their Lab color. Unlike CMYK, the preview is not (directly) based on measurements on physical prints, so it's not completely reliable.

When you convert from CMYK mode to Multichannel mode, the CMYK percentages of each pixel are unchanged. It's the exact same data as before, but the preview of the colors change because you change from color managed CMYK mode to algorithm based Multichannel mode.

This image shows how a neutral gray sRGB color (RGB(128, 128, 128)) converts to different CMYK profiles:

And here is how these same CMYK percentages looks in Multichannel mode:

If the printer you use doesn't use a color profile and wants you to deliver a CMYK file, there is no way you can get an accurate preview on screen. The result might be "something in between".

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  • Dear @Wolff can u explain further about this sentence?? "because you change from color managed CMYK mode to algorithm based Multichannel mode."
    – dayah_ML_malaysia
    Aug 24, 2018 at 9:06
  • I'm just summarizing what I explain above: CMYK mode uses color profiles so the colors you see on screen are based on physical measurements and the colors should match the print of a print house which uses that specific color profile. Multichannel mode doesn't use color profiles and the preview is based on a mathematical algorithm made by Adobe and is therefore less accurate. The image is the same - the same CMYK percentages, only the preview changes.
    – Wolff
    Aug 24, 2018 at 14:45
  • dear @Wolff I've edited my question. From what i see here the CMYK value did shift a bit but not as much as the Photoshop review..What concern me the most is if the customer didn't accept the color.
    – dayah_ML_malaysia
    Aug 28, 2018 at 6:49
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Before changing the Image Mode to Multichannel be sure the image is in CMYK mode.

When transforming a RGB image to a Multichannel, the black channel is missing:

enter image description here

CMYK image to Multichannel:

enter image description here

Image from unsplash.com

Edit after the question update

Don't duplicate the C-M-Y-K channels to make a C1M1Y1K1 Multichannel file.

  • From a CMYK image go to Menu Image > Mode > Multichannel
  • Change the channel's names after

dcs

I tried with a screen capture of your image and the colors vary significantly. I've got some similarity duplicating the C1 channel but this is not a solution.

enter image description here

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  • ive already change the mode to CMYK first..but still when i save the file to Photoshop DCS 2.0, the color shift either to be reddish/yellowish..gosh.. im new here..how to load the screenshot image here? heee
    – dayah_ML_malaysia
    Aug 23, 2018 at 8:16
  • At the bottom of your question you will see the edit button. After editing, at the top of the text area there's an icon to insert images.
    – user120647
    Aug 23, 2018 at 8:46
  • Ive tried ur suggestion, but how come ur file color didn't shift at all?mine result is the same exactly as before eventhough the step is different. (T.T)
    – dayah_ML_malaysia
    Aug 23, 2018 at 10:33

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