Which image mode to use

[Reddhare_]

Hi,

I am going to create a series of posters where all of them will have the same style:
a black and white image with a red (multiply blending mode) object on top.

My question is, which image mode is it best to work in? I want to use a black and white adjustment layer to give all the images the same type of black and white effect, but this adjustment layer cannot be used in CMYK mode. It can be used in RGB mode, but then it will be difficult to work with the exact correct red color (0,100,100,0), plus it eventually needs to be converted to CMYK mode for printing.

I have also tried first to work in RGB, then switch to CMYK before applying the red object. But then some of the adjustment layers disappears in the process. Any suggestions on how I should work with this?

I hope someone has a good idea on how I can solve this. Thank you 🙂

[Derek Cross]

Just leave it in sRGB colour mode – your desk-top printer's software will convert it to CMYK or CMYK plus, and if it's for commercial printing your printer will convert your PDF (PDF/x-4) or JPG to suit their requirements.

[Reddhare_]

Thanks! Do you think the black and white will be consistent enough across all the posters if I go for this solution? I might be overcomplicating things here, and the black and white might not get any color touches at all if I have used adjustment layers on it first 🙂

[Stephen_A_Marsh]

@Reddhare_ – A layered RGB working file makes sense.

Many print services will accept a copy as a flattened RGB file (please do embed the correct ICC profile).

If it turns out that you do need to provide CMYK, then they need to tell you what CMYK target/profile to aim for. Simply convert the flattened RGB version to the desired CMYK target condition, retaining the layered RGB working file.

Getting the red to 100m100y in the most saturated areas should be the least of your concerns. Ideally, you would use a high/strong GCR ICC profile variant to help safeguard against unwanted non-neutral colour casts/shifts in the four-colour black. 

https://www.colormanagement.org/en/isoprofile2009.html#coated_FOGRA39_GCR_bas

https://www.colormanagement.org/en/gracolprofile.html

https://www.colormanagement.org/en/swopprofile.html

[Reddhare_]

Thanks! I can work in RGB mode, then save the working version before converting it to CMYK and adding the red area. What I am wondering then is if the black and white areas will be printed in four colors instead of just black. Will the black and white will be consistent enough across all the posters, even if I use the right ICC profile?

[Stephen_A_Marsh]

It's not the file prep, it's the printing that may be variable.

You haven't stated the print method and you don't know if it needs CMYK as input and even if it does, what flavour/recipe of CMYK.

[Reddhare_]

You're right, I should check with the printer house to see what they require first.

[davescm]

I would work on the image in RGB (not greyscale) using your black and white adjustment etc.

I would then place that image in an INDesign document and add the red rectangle there which you can create using CMYK numbers for the fill. If you select the object and use InDesign's effects (Window > Effects) you can change the blend mode to mutliply as you appear to have done above.

Finally you can export to a PDF for printing - selecting Convert to destination (Preserve numbers) which will convert the RGB elements to the destination CMYK profile but won't alter the CMYK numbers for the object.

This method allows you to work with mixed CMYK shapes/text and RGB images.

Dave

[Reddhare_]

Thank you. It is a good soultion and I have considered it, but it's not every poster that has such a defined shape as in the example here. For example, in one of the posters I will need to highlight a close up face in red. Then I need to go in and adjust a bit, for example, by giving some areas more transparency. Therefore, everything needs to be done in Photoshop.

I can work in RGB mode, then save the working version before converting it to CMYK and adding the red area. What I am wondering then is if the black and white areas will be printed in four colors instead of just black. And if the black and white will be consistent enough across all the posters.

[Dani_James]

Work in **RGB mode** initially to use the black and white adjustment layer and apply the red object with the desired color effect. Set the red object to RGB values close to (255, 0, 0) for a pure red, similar to CMYK (0, 100, 100, 0). Once the design is complete, convert the file to **CMYK mode** for printing. Adjust the red object as needed to match the exact CMYK values. This workflow ensures consistency in the black and white effect and maintains the red color's integrity for print. Save the final file in CMYK for accurate printing results. I hope this will help you.

[Reddhare_]

That's a good plan, I think I'll go for this 🙂

[Lumigraphics]

This is not a CMYK job and no shop would offset print it that way. Its a two color job, black and red. You can use spot colors because that's what they will do on the press. If its a digital press, then just leave it RGB.

[Stephen_A_Marsh]

Posters will be printed digitally for smaller quantities - most likely inkjet or possibly on an Indigo. Offset would only be economical for longer runs.

[Lumigraphics]

Yeah the OP is unclear. I worked for a service bureau and the RIP for a Xerox digital press did much better with RGB files than CMYK. The printer should know. This would be fairly cheap as an offset run, only two colors and minimal makeready needed. No registration problems with a simple job like this and its much easier to match the exact red hue.

[Derek Cross]

Yeah, there's not much point in having the red as a spot, as that particular colour can easily be recreated with CMYK, and it's unlikely a spot would be available on a digital press anyway.