Retouching in CMYK and the 5 reasons I LOVE it

Yep, you heard me.

There is a wonderful flexibility in the CMYK color space that one just does not experience while working in RGB. It's like having that single extra channel frees up our color adjustment layers to work as the programmers intended. It makes RGB feel like a theater of blunt instruments.

To be perfectly transparent, I have to disclose the fact that I worked solely in CMYK for around 6 years. This was on very high level brand work that I guarantee you've seen at some point. Our goal was to make it perfect for print as that was the ultimate destination, whether in a magazine or on a billboard - digital was secondary. We didn't rely on service bureaus to prep our RGB files for print - we wanted control of the entire process from creative through to the prepress. In that case it made sense to work entirely in what we called interchangeably CMYK or 4-Color.

And oh boy do I miss those days. I'll quit reminiscing and cut to the chase, here are the top 5 reasons I love working in CMYK:

1. The Curves - In CMYK, the tonal information of each Channel is spread across 4 individual Curves. This is just flat-out more real estate than RGB, which is spread across only 3. This gives you so much more control when adjusting a Curve. You simply cannot make as precise Curve adjustments in RGB as you can in CMYK.
    
2. Again, The Curves - The magic of the way Curves work in CMYK is rooted in the difference between the 2 color models, one being a metaphor for Emitted, or Additive Color, the other for Printed, or Reflective Color. RGB, as an Additive model, creates colors by mixing together, becoming brighter as more is added, eventually mixing to create white when each value reaches 255. On the other hand, CMYK approaches black as color amounts are added. OK, this is all neat theory, but as this applies to the way a curve works in CMYK, by virtue of it being Additive as well as having a separate Black Channel, you can tweak the color of each Channel to your heart's content with much less distraction from Luminosity being tied to Color. For instance, if I want to warm up the 1/4 tones in an image, I simply target the 1/4 tones of the Magenta and Yellow Channel, anchor the rest of the curve, and very quickly adjust the color precisely in that area. Try doing that with an RGB Curve.
    
3. Plate Blending - The term Plate Blending originates in old-school prepress, which I'm definitely not qualified to get into here. But Plate Blending in CMYK was an incredibly powerful technique I would employ to add or create new structure in a Channel. For example, say you're retouching a shot of race car driver Tony Stewart wearing an annoyingly bright red jumpsuit, or whatever they're called. In the conversion to 4-Color, Photoshop is going to push most of the information to the Magenta and Yellow Channels, a little bit to Black (K), and almost nothing to Cyan. Because this thing is BRIGHT. Now that's, wonderful, it's as saturated as it can be in CMYK, but there's very little structure, very little tonal detail to give shape to the folds and volume of the garment. In order to force that, in CMYK you can simply rebuild the K Channel by replacing it with some detail that looks good. By copying information from another Channel, manipulating it with Curves or even Dodge and Burn, and pasting it right into the Black Channel of a new stamped-up pixel layer, you can make a brand new K to show all the lovely folds and Tony's svelte figure. I often wish I could do this in RGB. Try replacing a Channel in RGB with another and get ready to see the psychedelic color show.
    
4. Channel Mixer - Such a wonderful and powerful tool for what I call "purifying" color. In CMYK, if I want to maximize the saturation and purity of a brightly colored object, Channel Mixer is the magical tool to do it in a second. With Channel Mixer, I can tell Photoshop - "Wherever you find Magenta, please take all Cyan out of that area." And things like "Where you find Cyan, please add Yellow, and remove all Magenta." It's like Color Range in RGB, but works waaaay better. I'll be honest, I don't even use Channel Mixer in RGB. The few times I pulled it out to try to get similar results it looked like a nightmare immediately. Please someone tell me if I'm crazy here.
    
5. Ink Density - This is straying into Prepress world, but in 4-Color I can actually tune my image to the Printer's specs. I've prepped images destined for newsprint that was just about as strong as toilet paper. If you send off an RGB file to a Printer at full strength like that, the second-shift operator is most likely going to do your conversion to some CMYK profile where your image comes out looking like green dog food. Through a custom CMYK profile conversion with a maximum ink density of say, 140 (ack!), on my end, and Soft Proofing with Paper Color turned on, I can make that piece of dog food look as absolutely stellar as possible given it's eventual destination of a toilet paper substrate. You'd almost certainly want to send off a match proof for something like this, so if that second-shift operator at the printer just re-converts to his 140 profile anyway, you've got leverage to get a refund. If you're scratching your head going WTF is Sef talking about here, I understand - stories like this are becoming mythology.

That's it. If you're used to working in RGB, you don't even know what you're missing. These tools and techniques were so powerful and fluid, I miss them daily.

A Case for the Abolition of Working Space

According to some experts, "Every file has ten Channels." What they mean by that is RGB, Lab, and CMYK. This is true to some extent, in some workflows. But there is a whole new world of possibility in Photoshop that many of us have never even dreamed of. This is Blue Pill/Red Pill type shit. If we were truly freed of a working color space, we'd have complete and terrifying control over our images. Imagine having all those ten Channels accessible in a Curve dialog or Channel Mixer. There really would be no limitations to working Gamut, only the output intent. The concept of Soft Proofing would be much more widespread, and tuning an image for the best possible quality for different outputs would be much simpler.

In a perfect world...

So many Retouchers today don't understand that CMYK is a viable working space. Most just think of it as a thing they convert their file to when they want it to look like shit. Not true my friends - it is a color space like any other, just with a somewhat compressed gamut. But powerful and magical things can happen here.

One cannot call himself a professional retoucher without the knowledge of CMYK, I strongly believe.

So what are you to do if you don't have the slightest clue about working in CMYK?

Explore. Learn it. Become more powerful:

Here is a link to the most comprehensive text on the subject:

https://kit.com/sefmccullough/retouching-instruction/modern-photoshop-col (fyi this is an affiliate link to Dan's book through my kit website, and I get a small kickback for purchases through this link)

OK, I'm done shaking my cane at you.

PS - I have experimented with a wide-gamut CMYK profile which at first I was really excited about. After testing it out on a number of RGB images, I'm still seeing loss of quality somewhere around saturated 3/4 tones, kind of a flattening out and desaturation of the transitional areas into the Blacks. Enough that I would not work on an RGB image destined for web in that working space. I had high hopes at one time that this was a solution.

PPS - I have looked at Curvemeister and was also excited about that as a possibility - check it out, it brings a CMYK or Lab curve into RGB. BUT it's not an adjustment layer - you'd have to stamp up, convert to Smart Object, and apply as a Smart Filter to use it non-destructively. BUT I couldn't get it to load on my PC running PS CC 2018. :(

PPPS - Affinity Photo ?!?!?!