The group's techniques, 2


Dan Margulis
 



On May 19, 2020, at 10:11 AM, Roberto Tartaglione <roberto@...> wrote:

Dear Dan,
I've applied your method on more images of the same kind
and I can confirm from my point of view that is a very reliable workflow, it can easily 
be automated too. Of course, it can not solve all multiple problems of 
a conversion in CMYK, but there are many ways to finish the job.

Correct. Usually this method is a good one for brightly colored RGB files that can’t be matched in CMYK. We see, however, that it is not the best way to handle this particular job. Also, Rick’s method of using ProPhoto RGB as a channel-blending source happens to work well in an exceptionally brilliant image like this one. In more normal work it wouldn’t make a difference, and if it did sRGB would likely be a better choice than ProPhoto.

You also offered me an important food for thought:
"A CMYK fact of life: the lighter the desired color, the worse the possible gamut mismatch. If we were doing pink flowers the problem would be much more severe, and we’d see a lot more variation in the quality of our corrections.”
In my professional life one of the harder (or perhaps The Harder) object to photographers has been Wine Rosè (although I was not involved in the Pre-press), but this is another story...

If you worked in France, where the rosés tend to be a paler pink, you wouldn’t have the problem. Italian winemakers prefer their rosatos to have a distinct hue, which can indeed be tricky to portray in CMYK. Worse, when they see your CMYK result, they say “you didn’t seem to have any difficulty with our reds and our whites, qual è il tuo cazzo problema?”

Which brings up a second question, the answer to which brings up a third. The author of #209, stung by the criticism that he had made the red robe too orange, submitted a new version to prove he knew how to make it rosier if that’s what the client wanted. Granted that the original saturation can’t be matched, I don’t see why it’s such a big deal to change hue as well. Personally, I think that the orange version seems a bit more violent than the others and therefore preferable.

But, as one of you remarked, this is exactly the kind of image where you show the client multiple versions. Not just because they might or might not like the orange-red, but because they probably won’t believe you when you say you can’t match the RGB red, just as they say that when Roberto’s reproduction of rosé wine is no good. Seeing multiple versions might convince them.

That brings up a third question, posted to me offline. How can we force more detail into the yellow purse? It isn’t difficult, but there’s one catch.

It may or may not be necessary to select the purse, but one way or another you need to find the current channel with the most detail (which will certainly be the blue, in this case), make a copy of it, increase contrast so that its lightest parts are blank, and then paste into the purse in Luminosity mode at some low opacity, possibly with an MMM action later.

If this were a red purse and the robe some other color, this method would work well. But yellow offers a particular trap. If you make the red robe slightly orange, as in #209, it isn’t necessarily bad. Nor would it necessarily be bad to make it a bit more purple. With yellow, it isn’t true. Make the purse slightly warmer and nobody will object. But make any part of it seem to have a greenish feel and the job gets rejected.

It happens that as yellow gets darker, people start to perceive greenness. So here, understanding that the blend has to be subtle, I would not use Luminosity mode. Instead I would make the blend twice as strong into the green channel as into the red.

Dan


Rick Gordon
 

To clarify, I never left CMYK in my attempt, either. What I did — and routinely do in an action as part of my CMYK conversion workflow — is to pull off a flattened copy before conversion (I'd usually be coming from Lab), convert it to ProPhoto RGB, and copy the R, G, and B channels back into my working document, and then convert, so I have available pre-conversion R, G, and B channels to access, if desired.

I always choose ProPhoto RGB for this because there is far less likelihood of clipped or near-clipped values — and my workflow is in 16-bit, so I'm not concerned about the potential downsides of ProPhoto RGB — and the purpose is really just to get R, G, and B channels with detail throughout, for blending purposes.

Actually, as part of the same CMYK conversion action, I always pull a double conversion, one Relative and one Perceptual, which is then duplicated to Lighter Color and Darker Color. So the working result is:

  • Relative conversion on the bottom
  • Perceptual Lighter above that (disabled by default and usually not used)
  • Perceptual Darker above that, which I find almost always improves the shadows and blacks
  • A copy of the Relative in Color mode above that
I can then, if I want, do a stamp of the composite result in Normal mode below the Relative Color layer and then do channel blending actions, as if I were in Luminosity mode, which I don't need to be, because the color is protected by the Relative color layer. I could then stamp a composite of the result below the Relative Color layer, and blend another channel.

I've been very happy with the results of this action, which then also has various ready-to-engage curving actions built in above all that.

The general idea is to create a layered conversion that allows me lots of options already in place and available for use.

Rick Gordon

--------------------
On May 19, 2020 at 1:07:08 PM [-0700], Thomas Hurd,md Via Groups.io wrote in an email entitled "Re: [colortheory] The group's techniques, 2":
Although in my entries I transported back and forth between color spaces, I never thought to use ProPhoto RGB, but I will soon be trying it. The technique I described above never left CMYK after the initial conversion.

Tom Hurd
___________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________
WWW: http://www.shelterpub.com


Thomas Hurd,MD
 

Roberto, 

Thanks for offering up your image for us.

I also enjoyed and used Robin’s suggestion. In fact, I used it on the whole image, from the scratch conversion to CMYK, using fully saturated, no masking.

I duplicated the CMYK base image and then used Robin’s screen blend suggestion. Then I duplicated that layer twice to my taste for the highlights. I put those 3 stacked screen blend layers together in a group. 

Then I used a base layer duplicate on top of that and used multiply blend, opacity to my taste and more duplicated multiply layers, all for more shadows. I put the multiply layers in a group. I then decreased opacity of each group to control highlights and shadow. 
I was pretty close to what I wanted with a lot less work! So thank you Robin.

There was not enough cyan, however, so I duplicated the base layer and then blended about 20% of the yellow channel into the Cyan to give it enough weight to play around with. (Before channel blending, there was almost no cyan in the screen left arm.)

Again I changed opacity with the cyan fortified layer to get a level around C 6-8% on that red in the left arm. That was pretty close to the par image, and I am now experimenting with a curve on top of the whole stack.

It’s not all the way to the par image yet, but it’s close to it, and better than my original entries. And it just took about three minutes.

I’m looking forward to trying and experimenting with all the other techniques Dan described, as well. Although in my entries I transported back and forth between color spaces, I never thought to use ProPhoto RGB, but I will soon be trying it. The technique I described above never left CMYK after the initial conversion.

Tom Hurd


On May 19, 2020, at 10:12 AM, Roberto Tartaglione <roberto@...> wrote:


Dear Dan,
I've applied your method on more images of the same kind
and I can confirm from my point of view that is a very reliable workflow, it can easily 
be automated too. Of course, it can not solve all multiple problems of 
a conversion in CMYK, but there are many ways to finish the job.

You also offered me an important food for thought:
"A CMYK fact of life: the lighter the desired color, the worse the possible gamut mismatch. If we were doing pink flowers the problem would be much more severe, and we’d see a lot more variation in the quality of our corrections.”
In my professional life one of the harder (or perhaps The Harder) object to photographers has been Wine Rosè (although I was not involved in the Pre-press), but this is another story...

In the next days, I wish also try to experiment with another strategy: to process again my files from RAW into ProPhoto RGB instead of AdobeRGB and then to follow the same routine. It is interesting because I always thought otherwise, a few times in the past I converted the image in sRGB before CMYK to narrow the gamut before the conversion, obtaining no bad results.

I’ve also tested  the suggested  channels blending from RGB to CMYK, I think is a very successful technique that I never would have thought about, but 
I think it requires more experience, I mean it can be easier to worsen the image.
Last but not least, the tip from Robin Mark D'Rozario, can add a final touch to the image, I think
it will be useful for more than an image in my future workflow.

Once again I wish to thank Dan Margulis for focusing on this case and
to all the contributors who really helped me grow.

Roberto



Roberto Tartaglione
 

Dear Dan,
I've applied your method on more images of the same kind
and I can confirm from my point of view that is a very reliable workflow, it can easily 
be automated too. Of course, it can not solve all multiple problems of 
a conversion in CMYK, but there are many ways to finish the job.

You also offered me an important food for thought:
"A CMYK fact of life: the lighter the desired color, the worse the possible gamut mismatch. If we were doing pink flowers the problem would be much more severe, and we’d see a lot more variation in the quality of our corrections.”
In my professional life one of the harder (or perhaps The Harder) object to photographers has been Wine Rosè (although I was not involved in the Pre-press), but this is another story...

In the next days, I wish also try to experiment with another strategy: to process again my files from RAW into ProPhoto RGB instead of AdobeRGB and then to follow the same routine. It is interesting because I always thought otherwise, a few times in the past I converted the image in sRGB before CMYK to narrow the gamut before the conversion, obtaining no bad results.

I’ve also tested  the suggested  channels blending from RGB to CMYK, I think is a very successful technique that I never would have thought about, but 
I think it requires more experience, I mean it can be easier to worsen the image.
Last but not least, the tip from Robin Mark D'Rozario, can add a final touch to the image, I think
it will be useful for more than an image in my future workflow.

Once again I wish to thank Dan Margulis for focusing on this case and
to all the contributors who really helped me grow.

Roberto



Thomas Hurd,MD
 

Dan,

Thank you so much for managing this competition. For me, this was the very first time I presented a file to anyone in CMYK.
But it was great fun and challenging to come up with a file, even though I had no idea what to expect, just that I was trying to head as close as possible to the original impossible RGB colors as I could manage while stuck in CMYK.
Looking at all the entrants before the comments were posted, I agreed with what you, and many others, concluded. There were a lot of images that were close to one another and pretty good.
On Saturday, I just kept looking back and forth, saying “contrast, color” over and over. And I was most anxious to read everyone’s comments. And they didn’t disappoint. 48 hours later I know a lot more about color correction in CMYK. What happens when you add C, why do you add C, where does M100Y100 show up, etc. 
Before I run on (and on...), I want to say that 209 was my favorite, because I liked the color of red and there was good detail maintained along the yellow stripe. 
And for most of the last 2 days, I thought thought red was a bunch of nearly equal M and Y. Then I decided it was a little more M than Y, but C < 6. Today I think maybe it’s c16m80y70b??
It’s probably even tougher to look at a monitor for an hour, with no other colors around except a white background and a yellow bag, not enough to even give me a good excuse to bring up simultaneous color contrast. 
And now I just want to know: what is red?

Tom Hurd

On May 18, 2020, at 12:05 PM, Dan Margulis via groups.io <dmargulis@...> wrote:



When faced with multiple problems in the same image it pays to plan out the approach before striking out in all directions at once. Here, how much work should be done in RGB? How much in RGB? In CMYK?

Before seeing the image, I would have bet that, since we have a somewhat RGB-centric group, that’s where the fun might be taking place, whereas since I have more CMYK experience I might be doing more work there. It didn’t turn out that way.

Five of us determined from the get-go that we were going to make at least two versions of the image and then combine them. In four of these cases one of the versions had been desaturated, either slightly or completely. Unless I missed it in the notes, I was the only one who used Hue/Saturation limited to Reds, so as not to disturb the yellows.

Only three people applied RGB curves and only two of them were trying to affect overall color; notably in #209 there was a desire for a warmer, more orange red.

Only two people tried channel operations within RGB. Both wanted to boost contrast in the red channel, a good idea since that’s the one most responsible for shape when the interest object is bright red. One person accomplished this by blending the green channel into the red; the other by multiplying the red into itself. Neither version made it to our list of favorites.

When the image starts out this colorful, LAB doesn’t have many attractions, so few people used it. What’s going on? If people aren’t going to use much RGB, or much LAB, surely they don’t just convert into CMYK and get the disaster that is the default, #200. Or do they?

A CMYK fact of life: the lighter the desired color, the worse the possible gamut mismatch. If we were doing pink flowers the problem would be much more severe, and we’d see a lot more variation in the quality of our corrections.

Why? Since we can’t lay down solid magenta ink without creating a red rather than a pink flower, we rely on the paper itself to create lightness. This is unfortunate, since paper is not absolutely white; it reflects a certain amount of green and of blue light, both of which are red-killers.

The response of the experienced CMYK practitioner is that adding more ink allows a more colorful result, and that it is better to have the flower too dark than too gray. But exactly how dark to make it is a tough judgment call

When an RGB file is full of brilliant colors that CMYK can’t hold, it’s critically important that we get them as bright as we possibly can. Here’s my favorite trick, which I illustrated in CC2E with a picture of brightly colored cycles.

1.   Assuming approximately correct colors in RGB, make two copies and move them into LAB.

2.   Copy 1: desaturate it slightly until you are sure that nothing will be lost by moving it into CMYK.

3.   Copy 2: use Color Boost or similar action to produce colors so bright that you absolutely will lose a lot of detail on conversion.

4.   Place Copy 2 as a layer on top of Copy 1.

5.   Change layer mode to Color. No apparent change from Normal mode, since the L channels of the two layers are identical.

6.   Move into CMYK without flattening. Surprise! Suddenly the detail returns, because Color mode in CMYK tries to retain the structure of the black channel, which is responsible for a lot of the detail.

7.   Add another copy of Copy 2 to the stack and set mode to Normal, massacring detail once again.

8.   Reduce its opacity to the maximum you can stand. The higher the opacity, the more colorful, but also the more detail is sacrificed.

So by habit, I used this elegant procedure and produced a suboptimal image. Why? Because with a lot of colors in play, of various darknesses, it’s really hard to know whether we’ve gotten all the color possible. Not true in this Carnival image. Getting maximum color is a piece of cake, pretty much everybody did it. The robe is dark enough that if we push its maximum color to 0c100m100y0k nobody will care. It’s easy to do with CMYK curves. No need for all these gyrations when we can just attack the detail in the CMYK channels directly.

Three other people followed the above procedure. Meanwhile, eight people took the more direct approach of converting into CMYK followed by blends into at least the cyan and often the magenta channel. Of these, one (#210) used my LAB procedure as well. The other seven, AFAIK, just glommed the file into the terrible #200 default and then fixed it. One of the eight blenders took his blend source from within CMYK but the other eight used RGB channels as the source: at least the red into the cyan, and often the green into the magenta. That is a highly sophisticated technique that I wouldn’t have expected to be so widespread. It appeared in many of the versions we listed as favorites, including #203, #210, #211, and #214.

Some of these people also applied curves to the RGB channels to add contrast before blending with them. Particular kudos to Rick Gordon, who thought to convert the Adobe RGB file to ProPhoto RGB before using its channels as a source. ProPhoto has a much wider gamut and isn’t impressed by how red this image is. It therefore shows subtler detail in its channels than Adobe RGB does.

Beyond that there was some variation, but few surprises. Two of us experimented with different rendering intents on conversion. One person created an entire layer of 0c100m100y0k and used it, masked, for various purposes. Six people used CMYK curves, sometimes through a network of masks. Two used Selective Color to enhance the shadows.

All in all, an excellent group effort.

Dan

 

 

 

 

 

 

 

 

 

 

 


Dan Margulis
 

When faced with multiple problems in the same image it pays to plan out the approach before striking out in all directions at once. Here, how much work should be done in RGB? How much in RGB? In CMYK?

Before seeing the image, I would have bet that, since we have a somewhat RGB-centric group, that’s where the fun might be taking place, whereas since I have more CMYK experience I might be doing more work there. It didn’t turn out that way.

Five of us determined from the get-go that we were going to make at least two versions of the image and then combine them. In four of these cases one of the versions had been desaturated, either slightly or completely. Unless I missed it in the notes, I was the only one who used Hue/Saturation limited to Reds, so as not to disturb the yellows.

Only three people applied RGB curves and only two of them were trying to affect overall color; notably in #209 there was a desire for a warmer, more orange red.

Only two people tried channel operations within RGB. Both wanted to boost contrast in the red channel, a good idea since that’s the one most responsible for shape when the interest object is bright red. One person accomplished this by blending the green channel into the red; the other by multiplying the red into itself. Neither version made it to our list of favorites.

When the image starts out this colorful, LAB doesn’t have many attractions, so few people used it. What’s going on? If people aren’t going to use much RGB, or much LAB, surely they don’t just convert into CMYK and get the disaster that is the default, #200. Or do they?

A CMYK fact of life: the lighter the desired color, the worse the possible gamut mismatch. If we were doing pink flowers the problem would be much more severe, and we’d see a lot more variation in the quality of our corrections.

Why? Since we can’t lay down solid magenta ink without creating a red rather than a pink flower, we rely on the paper itself to create lightness. This is unfortunate, since paper is not absolutely white; it reflects a certain amount of green and of blue light, both of which are red-killers.

The response of the experienced CMYK practitioner is that adding more ink allows a more colorful result, and that it is better to have the flower too dark than too gray. But exactly how dark to make it is a tough judgment call

When an RGB file is full of brilliant colors that CMYK can’t hold, it’s critically important that we get them as bright as we possibly can. Here’s my favorite trick, which I illustrated in CC2E with a picture of brightly colored cycles.

1.   Assuming approximately correct colors in RGB, make two copies and move them into LAB.

2.   Copy 1: desaturate it slightly until you are sure that nothing will be lost by moving it into CMYK.

3.   Copy 2: use Color Boost or similar action to produce colors so bright that you absolutely will lose a lot of detail on conversion.

4.   Place Copy 2 as a layer on top of Copy 1.

5.   Change layer mode to Color. No apparent change from Normal mode, since the L channels of the two layers are identical.

6.   Move into CMYK without flattening. Surprise! Suddenly the detail returns, because Color mode in CMYK tries to retain the structure of the black channel, which is responsible for a lot of the detail.

7.   Add another copy of Copy 2 to the stack and set mode to Normal, massacring detail once again.

8.   Reduce its opacity to the maximum you can stand. The higher the opacity, the more colorful, but also the more detail is sacrificed.

So by habit, I used this elegant procedure and produced a suboptimal image. Why? Because with a lot of colors in play, of various darknesses, it’s really hard to know whether we’ve gotten all the color possible. Not true in this Carnival image. Getting maximum color is a piece of cake, pretty much everybody did it. The robe is dark enough that if we push its maximum color to 0c100m100y0k nobody will care. It’s easy to do with CMYK curves. No need for all these gyrations when we can just attack the detail in the CMYK channels directly.

Three other people followed the above procedure. Meanwhile, eight people took the more direct approach of converting into CMYK followed by blends into at least the cyan and often the magenta channel. Of these, one (#210) used my LAB procedure as well. The other seven, AFAIK, just glommed the file into the terrible #200 default and then fixed it. One of the eight blenders took his blend source from within CMYK but the other eight used RGB channels as the source: at least the red into the cyan, and often the green into the magenta. That is a highly sophisticated technique that I wouldn’t have expected to be so widespread. It appeared in many of the versions we listed as favorites, including #203, #210, #211, and #214.

Some of these people also applied curves to the RGB channels to add contrast before blending with them. Particular kudos to Rick Gordon, who thought to convert the Adobe RGB file to ProPhoto RGB before using its channels as a source. ProPhoto has a much wider gamut and isn’t impressed by how red this image is. It therefore shows subtler detail in its channels than Adobe RGB does.

Beyond that there was some variation, but few surprises. Two of us experimented with different rendering intents on conversion. One person created an entire layer of 0c100m100y0k and used it, masked, for various purposes. Six people used CMYK curves, sometimes through a network of masks. Two used Selective Color to enhance the shadows.

All in all, an excellent group effort.

Dan