screen printing > 4 Color and Simulated Process Printing

How to sep out Simulated-Process Color in Photoshop?

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Raw Paw:
Hello mighty warriors of the print realm,

I am very familiar with separating prints using Index / dither, as well as CMYK.  However, I have never learned how to do Simulated Process, which I understand to be a multi colored halftone image, created with spot colors, with no overlapping dots (as opposed to CMYK).  I know this has something to do with channels... which I am pretty unfamiliar with.  For CMYK separations, for instance, I switch the image mode to CMYK, which automatically separates what become the different Cyan, Magenta, Yellow and Black screens for me.  Once I have the channels separated, I apply the halftone pattern using "Image - Mode - Bitmap," and manually enter in the angles of each respective layer.  For Index color / dither, I switch from RGB mode to Indexed Color, and select my ideal colors using the "pallete" - "Custom" at 150 DPI, and the image is separated into 150 dpi pixels in a finite amount of colors.

Not sure where to begin with Simulated Process.. any help or hints would be very appreciated.  I've attached some links for what I'm looking to achieve, the shirt pictured was printed by Holy Mountain in North Carolina using HSA inks.  Also, could someone explain the advantages of Simulated Process?  Does it work better for underbasing than an Index separation or CMYK?  I was reading wet on wet is easier to achieve on a white underbase using Simulated Process, whereas with a Dither all of the colors would start to muddy together..  And CMYK on a white underbase has been a headache to ever get to work (it requires me flashing every color and wiping the bottom of the screen with every print, to eliminate dot gain... defeats the purpose of wet on wet CMYK printing).  I also love how the pictured print will never fade in color and avoids the issues of discharge, in terms of yielding a more vibrant print and avoiding fibrillation of the shirt fibers over time.  Any help is very appreciated

ebscreen:
Index has it's place but it's probably 1 for every 200 sim-process prints we do.
Generally speaking index will require more printed colors for an accurate reproduction.
Index seps are typically easier to create however, save for the underbase. Index underbase can be a bear to create.

Sim-process is how the shirt world rolls. Dots and even solids can overlap entirely. Selections from main composite image are made
(typically using "select by color range") and design is broken down into dominant colors with secondary and tertiary (and quaternary!)
colors made up from blends of them. Also, primary and secondary colors can be made drastically different depending on whether it is over
a base or not. That's one reason I strongly prefer sim-process with a base (any base) as opposed to straight discharge.

As for where to start:

Frog says we learn by teaching but I say we learn by doing!

Get you an image of medium complexity and start playing with color selections. That's really all
there is to it. Set your color selection channels to "Spot Color" and opacity of 5-65% depending on the ink/color.
IE your yellows will be at the lower range, and your whites will be at the upper.

Beginner underbases can be made by duplicating the image, converting to greyscale, making
selection of white, and saving to new channel in original image. As you progress you will learn where you need
more or less base depending on top color.

Get real good at it, then learn you'll never be as fast or as good as the guys that do this for a living, and start sending
it out.

hope that helps.

Dottonedan:
Eb made some excellent statements and suggestions.  I don't have much to add to that other than to use a traditional dot on the base of an index print.  Idex is dot next to dot. Fully underbased with a white dot. Yuk.
I've attached a pic of a stochastic (same square dot but mixes like sim process) print I did separations for a guy in Canada. Index is dot next to dot. We used a traditional halftone base of 55lpi on 230 mesh.  This allows the shadow colors to darken more (giving more life) or dimension to the print. With a solid dot over dot, you don't get any tonal transition and need to rely totally on the DPI of the print for your eyes to blend.  With Sim process, you are using shirt color, and ink blending of wet on wet...to gain a far more full color transition physically in the print process than jsut relying on the file resolution.  150ppi by the way, is low in my opinion. I use 233, on 305 mesh and 266 on 340 mesh.  These two mesh counts at that resolution and (with many colors), help create excellent prints. But at the cost of more colors, more setup time.

Raw Paw:

--- Quote from: ebscreen on February 07, 2020, 07:19:43 PM ---Get you an image of medium complexity and start playing with color selections. That's really all
there is to it. Set your color selection channels to "Spot Color" and opacity of 5-65% depending on the ink/color.
IE your yellows will be at the lower range, and your whites will be at the upper.

Beginner underbases can be made by duplicating the image, converting to greyscale, making
selection of white, and saving to new channel in original image. As you progress you will learn where you need
more or less base depending on top color.

--- End quote ---

Thank you very much for the detailed and thoughtful response.  I played around with an image last night and learned some things...  As someone who has used photoshop for around 13 years but has very little understanding of Channels, this is a whole new ballgame.  I got some ok results, need to keep researching and practicing.


--- Quote from: Dottonedan on February 08, 2020, 12:48:59 PM ---Eb made some excellent statements and suggestions.  I don't have much to add to that other than to use a traditional dot on the base of an index print.  Idex is dot next to dot. Fully underbased with a white dot. Yuk.
I've attached a pic of a stochastic (same square dot but mixes like sim process) print I did separations for a guy in Canada. Index is dot next to dot. We used a traditional halftone base of 55lpi on 230 mesh.  This allows the shadow colors to darken more (giving more life) or dimension to the print. With a solid dot over dot, you don't get any tonal transition and need to rely totally on the DPI of the print for your eyes to blend.  With Sim process, you are using shirt color, and ink blending of wet on wet...to gain a far more full color transition physically in the print process than jsut relying on the file resolution.  150ppi by the way, is low in my opinion. I use 233, on 305 mesh and 266 on 340 mesh.  These two mesh counts at that resolution and (with many colors), help create excellent prints. But at the cost of more colors, more setup time.


--- End quote ---

I think I am understanding you right, and I read someone else explaining this yesterday in my research, but this doesn't make sense based on what I have learned in my print experience...  You print a dither / index print, on top of a halftone underbase???  I could see this working really well, it had just never occurred to me as a possible option..  Very cool..  Thank you for sharing!  As for 150ppi, I should probably re-test my dither resolution, but with our setup, I have found at 150 dpi dither translates perfectly to a 230 screen, and also works well in that it is half of 300 dpi...  the standard resolution we request from clients is 300 dpi, so if I need to dither one aspect of a separation, but leave the other smooth and undithered, I can dither the selected portion in a new file, decrease the size in half from 300 to 150, then rescale the dither back up to 300 dpi using "image size - nearest neighbor."  Each dither square goes from 1x1 pixel to 2x2 pixels, and duplicates back into the original file seamlessly.  Beyond this, every dot consistently and reliably exposes to a 230 screen.  I found a dither dot smaller than that didn't lost a lot of clarity on our separation printer and we couldn't expect for every dot to expose to the screen.  We have a load of 300 mesh screens but I hardly ever use them, might have to try again

kidink:

--- Quote from: Dottonedan on February 08, 2020, 12:48:59 PM ---Eb made some excellent statements and suggestions.  I don't have much to add to that other than to use a traditional dot on the base of an index print.  Idex is dot next to dot. Fully underbased with a white dot. Yuk.
I've attached a pic of a stochastic (same square dot but mixes like sim process) print I did separations for a guy in Canada. Index is dot next to dot. We used a traditional halftone base of 55lpi on 230 mesh.  This allows the shadow colors to darken more (giving more life) or dimension to the print. With a solid dot over dot, you don't get any tonal transition and need to rely totally on the DPI of the print for your eyes to blend.  With Sim process, you are using shirt color, and ink blending of wet on wet...to gain a far more full color transition physically in the print process than jsut relying on the file resolution.  150ppi by the way, is low in my opinion. I use 233, on 305 mesh and 266 on 340 mesh.  These two mesh counts at that resolution and (with many colors), help create excellent prints. But at the cost of more colors, more setup time.

--- End quote ---

Looks great, can I ask why the decision was made to do this as a stochastic dot over a hafltone underbase as opposed to angled hafltone for each colour?
I'm assuming it was separted in the normal way and then converted to halftones using a RIP?

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