Colour correction in Photoshop for offset.

[budafist]

We have 4 tifs and photoshop eps files that we use for a monthly CMYK, offset magazine. The images are all CMYK and every month, the printer has to increase the yellow by about 20% on the press and tone down the magenta by about 20% to match the client's corporate colour. Since he is doing this solely to get these 4 images to print correctly, it means we sacrifice the colour for all the photos and other images throughout the magazine. It means all the other photos are too yellow and not magenta enough.

My task today is to change the tif and eps files so that the printer no longer has to do this.

How?

If I go into Hue/Saturation in Photoshop, and select Reds and/or Magentas and -20 on the Saturation scale, then +20 for Yellows on the Saturation scale, I can't see a difference on screen. I realise that I might not see a difference on screen but only on the press, but I'm not sure I want to send this out as "done".

Is this how you would do this?

Suggestions?

[Mynock]

Ughh. This problem makes my head hurt.

[budafist]

Did it also make your head go blue?

[Silence04]

Open the file in photoshop, go into channels and edit each channel appropriately using Curves.
In curves you can type in the percent you want to increase/decrease for ink coverage on that plate.

[Mynock]

Are you sure it's not the printers/press? Have you done other runs with it? Are you printing it at your shop or elsewhere? Did you create the files or the client? I guess what you will have to do is run some samples on digital and see if you can match the results and play with it there instead of doing press runs.

[Silence04]

make sure to have your Info pallet open so you can see the before/after ink percentages as your using curves

[budafist]

Open the file in photoshop, go into channels and edit each channel appropriately using Curves.
In curves you can type in the percent you want to increase/decrease for ink coverage on that plate.

Thanks Silence, I'll give that a whirl.

Are you sure it's not the printers/press? Have you done other runs with it? Are you printing it at your shop or elsewhere? Did you create the files or the client? I guess what you will have to do is run some samples on digital and see if you can match the results and play with it there instead of doing press runs.

The images were supplied by client as CMYK and it's possible that we are trying to match to previous jobs from someone else's press. In any case, they want the CMYK colours to match their spot colours as close as. Unfortunately, our digital is not close to our offset colours. If we're dealing with trying to match a colour on press, I might as well go by screen!

[urstwile]

This is where using the color sampler tool as opposed to the regular eyedropper tool comes in handy, as you click a target area and it keeps track of that area in the info palette.

[Danger_Mouse]

^exactly Urst, color sampler and selective color combo and that will fix that up right quick.

Create a small square with PMS color and color sample from that then tweak using selective color and paying attention to info pallette until you match it bang on. Use to do it all the time. Some colors may take more tweaking than others.

Had the problem of having images from different photoshoots in a catalogue. All colors on one page had to match other pages and be the company colors. For a forty page cataloque with 10 12 images per pages, it kept us busy. But worked like a charm, I was really impressed.

[budafist]

Create a small square with PMS color and color sample from that then tweak using selective color and paying attention to info pallette until you match it bang on. Use to do it all the time. Some colors may take more tweaking than others.

It took a bit of tweaking on all 3 sliders, but that was actually quite logical. We will have to wait until next issue when we get it on the press to see if it worked!

For now though, I'm just print a before and after to go on our proofer just to show the boss.

Thanks guys!

[HappyFriday]

Designers/clients like this really needs to get re-educated in color. If they bother to do some research, Pantone's Spot > CMYK process chips looks vastly different. Such request should never be allow and yet CSR always tries to please clients...

[budafist]

The client does understand that they won't get an exact PMS match on their colour when printing in CMYK. But we will still (and should) do our best to get it as close as we can. We've been doing it on the press for while, and it's about time we fixed the file itself.

Edit: digital proofs of before and after were pretty close to what we got and want to achieve on offset so my boss is very happy. :) Me too!

[HappyFriday]

Sorry, perhaps I misunderstood the initial post... what is their "corporate" color? Spot or CMYK?

[emucru]

Open the file in photoshop, go into channels and edit each channel appropriately using Curves.
In curves you can type in the percent you want to increase/decrease for ink coverage on that plate.

I don't mean to hijack this but I interested in this. Would using the channel mixer give the same results as doing it the way Silence04 mentioned?

[Danger_Mouse]

It took a bit of tweaking on all 3 sliders, but that was actually quite logical.

yeah it usually does, and depending on the difference and the color, you might have to apply it a few times over before getting result. Just try not to mess with the neutrals or blacks much.


Hey glad it worked. It saved a lot of grief when we applied it to our catalogue at the time. Although there were a lot of instances where we had to draw a path first and apply to selected area. It's also something you can't batch process, so if you have a shite-load of images you are doing some tedious long work.

[Silence04]

I don't mean to hijack this but I interested in this. Would using the channel mixer give the same results as doing it the way Silence04 mentioned?

Yeah, Channel mixer will give you the same results.