channel solidity numbers and why?

[srabadan]

We are looking to standardize some of our separation procedures. I am interested in what numbers you use for the solidity settings on your channels/colors to give you the best representation of how the colors will look on the shirt. Also interested in WHY you choose those settings.

Thanks!

[ol man]

70/80 percent on the underbase( depending on the art, simulated highmesh get a lower opacity)
20 percent on over print colors

Why? Saw it on the old board - tried it and it seems to work well

[Colin]

The problem with photoshop channel seps is that dot gain and opacity is never displayed properly.

So if I want to see what my wet on wet blending/opacity will look like, I need to reduce my channel opacity down to 2-5%.  If I am printing an opaque color, then I have a high channel opacity.  A translucent color?  Low channel opacity...

Noticing a trend?  Nothing is standard.

Take your last photoshop separation - that was printed - and bring it into your art room.  Adjust your channels until you match on screen what was printed.

Conversely, when you are printing your next separation.  Print EACH COLOR - SEPERATELY - DIRECTLY ONTO A BLACK SHIRT.  For each color, do a print and cure it.  Also do a print and then simulate a wet on wet print run - I.E. hit it with a blank screen/smoothing screen to push the ink into the shirt.

Now take both of these shirts into the art room and preview the same color on your monitor on a black background.  Adjust channel opacity until you have a match.  This should help get you into a ballpark for max and minimum opacity for that color. 

Next:  Bring in a full printed and cured shirt and compare those opacities again.

By the time you are done, you will have a better understanding of what ink does on press and on the shirt.  This will help you to trouble shoot and prepare for future seps.

I hope this made sense, I wrote it out off the top of my head to help explain the many nuances.  Hopefully someone can fill in some blanks :)

[JBLUE]

The solidity is always a little different for each sep. I look more at the percentages in each channel more than the solidity as the solidity does not represent the actual percentage of color. There is really no standard procedure for me because every piece of art is different. This is pretty hard procedure to standardize if not impossible. That is why the sep programs can only do so much and require each sep to be tweaked a lot.

[mimosatexas]

The problem with photoshop channel seps is that dot gain and opacity is never displayed properly.

So if I want to see what my wet on wet blending/opacity will look like, I need to reduce my channel opacity down to 2-5%.  If I am printing an opaque color, then I have a high channel opacity.  A translucent color?  Low channel opacity...

Noticing a trend?  Nothing is standard.

Take your last photoshop separation - that was printed - and bring it into your art room.  Adjust your channels until you match on screen what was printed.

Conversely, when you are printing your next separation.  Print EACH COLOR - SEPERATELY - DIRECTLY ONTO A BLACK SHIRT.  For each color, do a print and cure it.  Also do a print and then simulate a wet on wet print run - I.E. hit it with a blank screen/smoothing screen to push the ink into the shirt.

Now take both of these shirts into the art room and preview the same color on your monitor on a black background.  Adjust channel opacity until you have a match.  This should help get you into a ballpark for max and minimum opacity for that color. 

Next:  Bring in a full printed and cured shirt and compare those opacities again.

By the time you are done, you will have a better understanding of what ink does on press and on the shirt.  This will help you to trouble shoot and prepare for future seps.

I hope this made sense, I wrote it out off the top of my head to help explain the many nuances.  Hopefully someone can fill in some blanks :)

Awesome post!

[Dottonedan]

Well, I would have had a very loooong post to make to explain it, but Colin's does it justice.

I would say tho, that I stick with 65% on the underbase and the top colors fluctuate between 10-20% on top colors depending on the ink brand. Black and a top white is 100%.

[ol man]

The problem with photoshop channel seps is that dot gain and opacity is never displayed properly.

So if I want to see what my wet on wet blending/opacity will look like, I need to reduce my channel opacity down to 2-5%.  If I am printing an opaque color, then I have a high channel opacity.  A translucent color?  Low channel opacity...

Noticing a trend?  Nothing is standard.

Take your last photoshop separation - that was printed - and bring it into your art room.  Adjust your channels until you match on screen what was printed.

Conversely, when you are printing your next separation.  Print EACH COLOR - SEPERATELY - DIRECTLY ONTO A BLACK SHIRT.  For each color, do a print and cure it.  Also do a print and then simulate a wet on wet print run - I.E. hit it with a blank screen/smoothing screen to push the ink into the shirt.

Now take both of these shirts into the art room and preview the same color on your monitor on a black background.  Adjust channel opacity until you have a match.  This should help get you into a ballpark for max and minimum opacity for that color. 

Next:  Bring in a full printed and cured shirt and compare those opacities again.

By the time you are done, you will have a better understanding of what ink does on press and on the shirt.  This will help you to trouble shoot and prepare for future seps.

I hope this made sense, I wrote it out off the top of my head to help explain the many nuances.  Hopefully someone can fill in some blanks :)

 nice -- im on this... thank you

[srabadan]

Great stuff everybody, can't say thanks enough.

I work with a team of about 20 graphic designers in a studio environment, the creatives are far removed from the printing process and this can cause some predictable problems as their work moves from screen to tshirt. I am sure some of you have  more than a little experience managing those expectations.

The art director and I would like them to develop some experience separating their own work and we've tried to automate some aspects of the process without having to get too technical with them. It really is an art form all it's own. I think if we can establish a baseline for some of these things, we have enough ppl on the team with prepress experience to help them make the final tweaks to get each print ready for production and minimize surprises.

Thanks again!

[Colin]

Srabadan:

Their best and most lasting separation knowledge will come when you take them to the production floor and have them assist in ink mixing/set up/trouble shooting/production of seps that they have either done or had a hand in.  They will need a tactile/hands on experience to really let all that book knowledge sink in.

Otherwise it's all theory and no practice.

I myself started as a printer.  I know Dan has intense working knowledge of how inks actually flow and print.  Most of us who separate have a good to great grasp of the mechanics of printing high end stuff.

I have worked with to many "Artists/Creative types" who will not get it until you shove their faces into a press...

Well, maybe you don't have to go that far.... but I strongly encourage you to get them some production type experiences so they have some fundamentals of whats going on :)

Welcome to the Craft Industry called screen printing :)

[myseps]

Here's what i use and seems to work well in most cases:

base white, black- 100%
top white- 70%
grey- 50%
all other colors- 20%

[ravenmark]

I preview in Photoshop 5.5 using selected areas in channels with a black Background. After the change in the way things previewed in version 6 it became a spot color guessing game. Eventually I an going to have to start playing it when my 5.5 stops working on some future OS.

[Full-SpectrumSeparator]

I need to take a look at whether this was the change that happened in version 6 from 5.5 as mentioned,  or if that still has issues.

These files are a start, but will basically point out the errors. 

I have dug deep all the way to bottom of this issue, and of course the foundation itself is rotten, and you can't fix it.   But you can work around it in certain ways.

This color-blend / dot-gain-preview / % linearity  issue with the channels is not just in channels, but greyscale, duo-tone, and cmyk modes as well. 

So you can basically only make an accurate preview or working method completely for multi-colors where you have light and dark inks and shirt colors, and ink opacities, and want to simulate how they blend together and also put dot-curve simulations and compensations on them... if you build this in layers to work and simulate it all correctly.

It is more complicated then in layers of course than in channels, but it actually works, whereas channels can only be accurate in certain situations-- and only to the preview using the attached -Correction- Curve profiles,  so then you can't really put new curves on the already-applied preview curve to correct it.   

1:  You have a white or light-color background with a black ink.   Use the Dot-gain correction curve for DARKS.    This will at least correct that black ink channel to preview correctly in the view,  so a 50% looks like 50%,  etc,  and you could then use a curve (but it will be destructive) - to simulate your dot-gain response if you know it -- but you don't really want to apply that (the purpose of a preview if it worked correctly then channels would be very useful, maybe it did work in photoshop 5.5 correcty, I'll have to see) -- you would apply however you actual dot-compensation curve - sort of the inverse data from your measurements of the dot-response curves.

2:  You can blend in other channels with that mode, over the white background, and darker colors and shades will still preview relatively accurately...

3:  You have a black or dark shirt color background and a WHITE ink (or light colors/tints of colors - set to 100% opacity/soliditiy) -- then you would use the SEPARATE PROFILE for the  Dot-Gain Curve Correction for LIGHTS.    The same applies as how it works with the dark ink channels... it will correct it for viewing those channels alone or a few together.

--- The problem is you cannot use BOTH profiles - or use them independently on the different inks.

     You shouldn't have to,  because the other profile attached - ZERO DOT GAIN --- should give the same exact result for both dark and light inks -- you are simulating the ink blend response curve - or trying to - based off a linear starting point where what you put in is what you get - FLAT LINE from 0 to 100.   

So you can see if you put the flat-line profile in,  dark inks over light background will appear too FADED - as if they will have DOT LOSS -- and the light inks over dark background will appear very filled in - with massive DOT GAIN --- even though you are telling it to give you a flat response for all.    Now if you correct the darks it makes it darker and then the whites are even more filled in,   if you correct for the whites they are normal and then the darks are even more faded out.

You can't then preview light inks and dark inks and over light or dark shirt colors all together, and therefore why does the industry insist this is some sort of "standard" and then attempt to build logical workflows around it?   

I struggled for years attempting to do what most of you are trying to do, and then when I accomplish new standards it is just vehemently opposed, then in threads like this you are all aware of the same exact issues and trying to find solutions, which already exist if you are willing to learn how to use the program to avoid the mathematical flaws that will always make your job harder if not impossible to standardize.   

If you're ready to have this discussion then start with seeing that I have made dot-gain preview CORRECTION CURVES for mutlichannel mode, but the very fact you can do this proves how far off the channels preview and the whole dot-gain settings are and why it makes it impossible to get a full accurate preview of your separations.

If you can just follow the logic for a moment.. 
-You are in a working environment, simulating your art and your print.
-You want to know what to "tweak" or "adjust" to make your print come out right - like the art or as close as you can get.
-What if you can view your art in a method where it looks like what you will get?
-What if you can also view your art in a method that it will never look quite like what you will get, and even be oppositely off from what you see to what prints?
-Now let's say you make a print from separations using the math of the color blends from the image, and you linearize your outputs and you achieve a very great print without really tweaking or adjusting anything but ensuring your screenmaking and printing process are accurate to what you feed them....
-- So what if the preview of your color separations in the mode where it looks like what you will get -- actually looks like the print you made....
    And the other preview in the mode where it never looks correct -- looks off -- it looks INCORRECT and yet you printed the same math, the same information, the same halftones etc, and the print comes out like it looks in the OTHER MODE - where it looks accurate. 

Now which color mode is inaccurate or wrong?   The one the print looks like, or the one the print doesnt look like??

What if you told someone they have to work in the incorrect mode, and to just try and make it look "close enough" to the original, but it can never look like the original, and that they should start with something --- and what if the separation they are starting with is actually ALREADY CORRECT... ?     

Now what is happening when there is no accurate simulation, and even when you might have a separation that will print amazing and very close to the original, it will actually look WAY OFF, not just a little off, and therefore you'll always change that one, "Tweak" and "adjust" and curves this and that, not really knowing exactly why or what you're doing logically, but sort of using lots of fancy tricks and "Artistically" pushing the mode to work so you can at least feel you've done something and somehow it should help...??       The entire process has actually wasted hours of time, and made the separation WORSE than when it started, and further off from the goal of the original or coming close to it.

"Do not make the mistake of the foolish carpenter who wastes valuable time squaring, measuring, and smoothing his worm-eaten and inwardly rotting timber and then, when he has thus bestowed all of his labor upon the unsound beam, must reject it as unfit to enter into the foundations of the building which he would construct to withstand the assaults of time and storm."

If you're ready to build better standards and level foundations then we can work together and make everyone's tasks more efficient, more fun, more repeatable, better prints, lower costs, happier clients. 

If it ain't broke, don't fix it...   well it was broken and we can fix it, or work around it.   It's not that hard to show and preview the separations correctly in layers, then you can even work non-destructively and apply independent opacity and dot-gain simulation and compensation curves, make edits and adjustments etc with layer-masks.... there are so many more reasons why it makes sense to just ignore everything about working/editing separations within the channels, and only use them if you have to because it sends to a RIP more easily as all seps at once, but you still want to control your halftones and where they print in relation to each other, and the separations of course...  but on this channels/solidity/numbers/dot-gain and attempting to standardize...  we really need to be honest and accept the facts, and move on and find modes and methods that actually work and don't actually fight against you.   

I can take any channels separation - the best one ever made - and show how its inherently incorrect to what you get on press and what it actually looks like with the same settings but applied in layers so it shows accurately what was sent,  and the shirt probably didn't look like the channels... but everyone just says "Wow we are amazing we actually accomplished making a level building with curved rulers!... it doesn't look exactly like the blueprints, but hey close enough!"    This is not satisfactory for something calling itself a "professional industry."       

When you routinely see automated color separations done with just a few clicks of the right tools, all the way to halftone RIP - that come out BETTER THAN the "hand-made" color separations that a professional separation "artist" spent 8 hours working on, and it uses 3 more colors than the automated one and still doesn't look as good...   it is more than just some technical science thing... it is a major impact on the bottom-line and efficiency, repeatability, you WILL make more money, your artists will focus more on art, production will focus on printing, separations will be a breeze.    It is not meant to be oppositional to the "traditions",  I was a "high-end simulated process" separator at a high-end shop overseeing 5 other full time artists, sending to DTS machines and thermal imagesetters,  printing museum-quality and custom prints that were color-critical demanding, and trying to use all the methods at my disposal, but trying to follow some sort of logic of working with channels and the "software that gets you 70% there but you gotta tweak for hours to get the rest" --- yeah trust me I did all that for years, and I could not just work in an inherently flawed tool and maybe I strive for a higher standard or more accuracy and not blindly trusting a wildly incorrect tool - like using a curved ruler and being asked to make straight lines, then patting yourself on the back for making straight lines using only curves - - it is just insanity and I could never find a workflow that made sense, because there isn't one if you insist on using channels to preview/simulate and make edits/adjustments/tweaks and attempt to get colors to blend to make a simulation of a print like your original.   

The files attached are a start and we'll go from there with this topic... they prove you have an inherently oppositely-distorted issue with the spot-channel previews of gradient information.      I work greyscale, duotone, CMYK or "multichannel" like color separations -- all of that work I perform in RGB MODE and controlled simulations of the other modes, to avoid what is essentially a total DANGER ZONE for true color and print professionals.   Even CMYK in photoshop and illustrator suffer from preview issues with the paper print modes they are supposed to simulate accurately as well, but that is the larger industry usage and they are at least a little more standardized and accurate.    But none of the modes were ever designed for screenprint in the first place, but you can use the mathematics of light and color simulation in RGB layers to simulate other modes accurately.   You can simulate and separate in RGB to CMY, CMYK, WCMYKW,  etc etc... custom colors, even index you need to preview in RGB...   the only purpose I ever have for channels is if I had a RIP that I wanted to send pre-halftoned images to just print more automatically instead of sending one layer at a time to print.      Working with epson film printers that doesn't really matter and especially digital LCD I would just view a layer and expose it, no need for some channels mode to send files out to a printer.   

I'll come back after looking into photoshop 5.5 - I know that is when they put in some CMYK estimate-overprints functions and I think that math along with the dot-gain previews is what threw it all off...  there are a lot of things to expose to avoid as color and print professionals within programs like photoshop -- upsampling is another major color-destructive process, like JPG etc only in the opposite direction.   But with dot-gain and channels/solidity etc,  this thread is just hitting too close to the mark and it always pains me to see the struggles of others where I have already worked through all this.    I'm not selling snake-oil or anything, this is all very real and more than just some technical experimentation, it has been cut out over years of real trial and error and work, making all the same mistakes over time and I am just not the type who likes to make mistakes, I am an extreme perfectionist, but I am also a stickler for extreme efficiency....  my work is the result of not stopping and accepting the same old "this is the way we've always done it" routine.   I'll play nice, but I won't work with rotted tools or pretend they aren't.    If you understand my energy and passion and yes anger at times, is attempting to be channeled and has been, creatively with solutions... anyone can point out the problems, I don't just come around to point out the problems and say "you're doing it wrong" etc... that would be truly acting like a jerk,  and I'm not just waving around saying look my way is the best etc and trying to sell something on that...  just seeing the posts in this thread tells me others are ready to accept the facts and that there is a demand for better methods and standards, people are facing the same struggles as I have, and I feel they should have the tools and teachings that are a result of not just wondering passively and complaining about the problems, but digging down further and further into the tools, the processes, art, color, printing... but when you discover that an entire working mode of a program, like for example let's say you discovered every time you drive your car in reverse you have to steer right to go left, and left to go right, and then you discovered the gas also gets wasted more and you can only go 15 miles per hour instead of 50.... then you have a race or a trip to make and the industry or your employer tells you well look we need to make this trip.... you say well there is this other mode where I can drive in forward and go a lot faster and make less mistakes over-correcting because left goes left, right goes right... and we will save on gas even though we are going faster and the stuff will get there in quicker time and be fresher actually...  ...  but then the industry says well you're wrong, no, thats the way we've always done it and driving in reverse is an industry standard and who are you to say there is a better way and we're all driving backwards??    Oh well...  no use looking in the rearview now.  :P

[Dottonedan]

Spectrum,

Sphoowh!  That's a lot to take in.  Did you post up some preview scripts for layers somewhere or is that something you're "going to do" later? Maybe I'm missed it or miss read. Sounds like something you already did somewhere.

We all agree that Photoshop has not ever had an option or process for a true representation of dot gain...(for screen printing).  There are just too many variables that we don't control in the art department. To be most accurate, You'd have to have all things considered and locke din (in advance) for each job for any attempt to be as true as you can get.

Mesh selection plays a factor for one thing, even squeegee duro, angle, number of colors going down on a base or no base, Ink type/ink modification) etc. each way looks different. I'm aware you're aware of this.  Having a simulation even within layers and a choice of the best modes and methods seem to be a reach to me, but then gain, I'm speaking as someone who's not dabbled into the area of layer modes and (for that purpose).

In fact, I've never printed seps from layers. I've heard that some sep programs like UltrsSeps does use layers (I think) but not sure. Someone had told me before that they have ONLY ever printed from layers so that would be interesting. Maybe they were only ever using this sep program. Still, even that seems odd to me at this point.

To take a RGB layer of say Gold pms 137 and have it come out of your RIP not as CMYK representation, but as a spot color. And of that, how does that RGB fade with accurate percentages?  In those cases, if your RIP is linerized, is the RGB layer Gold pms 137 (area filled in at 10%) actually 10% after converting the rgb to the spot? It would seem that the % used to make up the 10% area would be combining each % needed from the R, The G and the B.

Does it fade with a compounding action of RGB as for example, (the layer modes add or subtract or multiply color). How does layers treat a color at output as a correct or exact % of a spot color that an area should be?  Is it a grayscale equivalent or some action script going back some form of spot channels in the end and then finally to the RIP? Either of those don't seem as accurate as a spot channel where I can see that the 5% fill is a 5% fill and when I read it after it's been ripped with the densitometor, the 5% is still the 5% needed.

Previewing, to me is a different beast. The need is different. My only intent or need for an accurate preview is if doing a color print and we know there are many methods to do so pretty well but even that needs calibrated. When I'm doing seps, Sure I look at the overall preview but I don't expect it to ever be accurate for the reasons stated above.

I read numbers. I base my adjustments off of what I see is in the seps. I had always had a (color print file) when needed and a production file. Both gave extremely different looks. If I were to create and separate out of layers only, and never touch channels, I don't know how I can assure myself that my %'s would (come out) accurate from the layers to RIP because the layers gives me reads of RGB. That's another story different from what you're talking about but I figured you'd be able to shine some light on that process.

[Full-SpectrumSeparator]

Spectrum,

Sphoowh!  That's a lot to take in.  Did you post up some preview scripts for layers somewhere or is that something you're "going to do" later? Maybe I'm missed it or miss read. Sounds like something you already did somewhere.

We all agree that Photoshop has not ever had an option or process for a true representation of dot gain...(for screen printing).  There are just too many variables that we don't control in the art department. To be most accurate, You'd have to have all things considered and locke din (in advance) for each job for any attempt to be as true as you can get.

Mesh selection plays a factor for one thing, even squeegee duro, angle, number of colors going down on a base or no base, Ink type/ink modification) etc. each way looks different. I'm aware you're aware of this.  Having a simulation even within layers and a choice of the best modes and methods seem to be a reach to me, but then gain, I'm speaking as someone who's not dabbled into the area of layer modes and (for that purpose).

In fact, I've never printed seps from layers. I've heard that some sep programs like UltrsSeps does use layers (I think) but not sure. Someone had told me before that they have ONLY ever printed from layers so that would be interesting. Maybe they were only ever using this sep program. Still, even that seems odd to me at this point.

To take a RGB layer of say Gold pms 137 and have it come out of your RIP not as CMYK representation, but as a spot color. And of that, how does that RGB fade with accurate percentages?  In those cases, if your RIP is linerized, is the RGB layer Gold pms 137 (area filled in at 10%) actually 10% after converting the rgb to the spot? It would seem that the % used to make up the 10% area would be combining each % needed from the R, The G and the B.

Does it fade with a compounding action of RGB as for example, (the layer modes add or subtract or multiply color). How does layers treat a color at output as a correct or exact % of a spot color that an area should be?  Is it a grayscale equivalent or some action script going back some form of spot channels in the end and then finally to the RIP? Either of those don't seem as accurate as a spot channel where I can see that the 5% fill is a 5% fill and when I read it after it's been ripped with the densitometor, the 5% is still the 5% needed.

Previewing, to me is a different beast. The need is different. My only intent or need for an accurate preview is if doing a color print and we know there are many methods to do so pretty well but even that needs calibrated. When I'm doing seps, Sure I look at the overall preview but I don't expect it to ever be accurate for the reasons stated above.

I read numbers. I base my adjustments off of what I see is in the seps. I had always had a (color print file) when needed and a production file. Both gave extremely different looks. If I were to create and separate out of layers only, and never touch channels, I don't know how I can assure myself that my %'s would (come out) accurate from the layers to RIP because the layers gives me reads of RGB. That's another story different from what you're talking about but I figured you'd be able to shine some light on that process.

Yeah, very quickly as I have a lot of screens to make and printing to run today, as well as some fun LCD tests (just bought a little 100watt Metal Halide floodlight to test)...  but indeed you can't just send RGB / regular print-mode of the RGB separations to a RIP device/printer output...    Definitely I am aware of the advantages and uses of printing directly from channels where each sends out as black and white information or the greyscale percentages that translate through the RIP.      And there isn't really an automatic way to do this from layers,  that is not necessarily how I output...  for example often with the small-shop low-level equipment I'm working with here, we just have two epson 1430 printers with default inks, and I tell the prints to be CMYK mode with 100% for each channel, to get dark films that expose halftones etc for me relatively well on a fluorescent-bulb vastex exposure unit set to about 4 minutes with Saati textile pv emulsion.    The whole process is really the same when it comes to output - you are still getting your greyscale information as % to transmit to a RIP - or in my case I usually take my separation automations into RIP within photoshop - and this is the further advantage when I am making final edits and working with all the simulated inks as their halftones in color and getting full comp/previews...  in layers - whether it is greyscale information on the separation or ripped to halftones - this will still be changed to preview as BLACK and then printed in CMYK for a manual RIP --- or I can just transfer these separation layers back over to channels (not trust what I'm seeing - but yes you can trust the eyedropper - IF you have it set to the right color modes and your color settings match the readings with the right profiles) --  everything is essentially the same,  but when ready to output we don't currently have methods to print each layer separation as -changing to greyscale- all of them at once, during print to the RIP device -- what I will do is either just copy them back over to channels or output as black from the layers - changing the ink of the layer to be a CMYK black.

I'll get back to the other great stuff you mentioned later...   but one of the things I would like to clarify or I can show examples and we work to determine if these inferences are correct, but basically if you are in the right RGB viewing mode - so your monitor profile and your photoshop profile match,  and your gamma correction sets the linear RGB to appear as the right luminance levels through the monitor,  then if you were to view a greyscale gradient,  this is representing how it would also appear if you printed halftone dots with perfect dot-compensation control - or the exact dots you made printed exactly --  if you do the research you will find that gamma correction is for rgb and was built around CRT issues,  and there is no gamma correction to linear data being transferred to halftones -- it is a halftone-compensation function and they called it dot-gain... so you are using gamma correction to view the normal greyscale or rgb information...  even the other greyscale and multichannel and cmyk for offset and other printing purposes has issues with the dot-gain function, they actually put it all into the programs incorrectly by not taking into account the difference between gamma correction and dot-gain correction.    The human visual system has a function called Contrast-Sensitivity-Function and through visual acuity summation distances we blur halftones or gratings / frequencies into smooth continuous tones...   That also is what makes halftones a completely different thing than luminance levels.      But that is all very deep stuff... however, I will help to show that you can "linearize" your working modes between RGB, greyscale (use the SGrey dot-gain profile, or use RGB mode simulate the grey and use more accurate dot-gain preview and compensation curves) -- CMYK simulated, and multichannel or duotone etc simulated accurately.      Essentially with RGB the numbers all stay the same from 0 to 100% or from 0 to 255,  and that is your greyscale gradient as well, how it views the same is about matching the profiles right as you want any computer graphics color management working mode to be calibrated...  you can set your RGB info eyedropper etc to read from RGB and have it show you the K% (if the profile is set right it will show a correct translation) or HSB - Brightness is the same % as your black or ink level etc ---   you don't print the RGB layer separations as the colors if you're viewing them in color - -usually I have a color-overlay set so when i turn off the color overlay it is viewed as a separation in black.   

The blend-modes in RGB can simulate additive light as they already work that way in the channels -- but you can simulate subtractive or additive or any mix between with layers and it is just the final color-view that is using RGB channels to display to the monitor etc,  but for output you either copy back over to channels or have your view mode in CMYK or know that your RGB black when you set the sep to view that way will output to the right CMYK or black ink %,  but I Can set it to greyscale or CMYK in my case and force CMYK #s to stay as I set them to the Epson printer because of not using a RIP,  but also like I mentioned it is the same information when you copy a channel or layer correctly from RGB or greyscale over to multichannel or back...  so I can just bring over to channels the finished editing separations and output to a RIP if that device requires or it is more time-saving that I Can send all at once and it starts printing them all out.

Let's start with maybe covering that whole greyscale linearity between modes or simulating it all and it translates out how you want it topic before going further into the curve-simulations.   How the RGB #s are linear greyscale information in the neutral axis from 0 to 255,  and how to view it all so that gamma correction and dot-gain are working together and not against each other or not being taken into account at all and are an unknown in the calibration process.