Photoshop Tone Separation Ques

[BillA]

We used to do a lot of this in screen printing, both with film masking and in Photoshop, building 8-12 color prints on black tshirts.

We used to start with a few of sets of identical files side-by-side: CMYK, LAB and RGB. Find the channel that most matches the density area you want to pick out, inverting as needed.

Add that into your master file as a new channel. Adjust levels to get a close approximation of your area. Use the Quick Mask to cut out the rest as you would with RubyLith.

You should be able to preview your image by assigning it an index or preview color. This will give you a reasonable approximation of your final print.

I hope this helps. I have a friend who is a color separator that might be able to help if you need it.

Kind regards,
Bill

[BillA]

Here is an example. I pulled the shadows from the K plate of a CMYK version, brought it into the master RGB file and colorized it as green to show where the second hit of shadow would fall.

[bob carnie]

Bill

this is pretty much how I am doing right now. I am thankful for all responses,
I did not think that this would be such an odd question.
I have asked on four forums and now have about 15 methods to try, this may take some time.

We used to do a lot of this in screen printing, both with film masking and in Photoshop, building 8-12 color prints on black tshirts.

We used to start with a few of sets of identical files side-by-side: CMYK, LAB and RGB. Find the channel that most matches the density area you want to pick out, inverting as needed.

Add that into your master file as a new channel. Adjust levels to get a close approximation of your area. Use the Quick Mask to cut out the rest as you would with RubyLith.

You should be able to preview your image by assigning it an index or preview color. This will give you a reasonable approximation of your final print.

I hope this helps. I have a friend who is a color separator that might be able to help if you need it.

Kind regards,
Bill

[bob carnie]

Hi Bill
good example, now if you invert that to negative I am sure it is close, Is that a black car or is it red? Therfore It would be considered the shadow neg?

Here is an example. I pulled the shadows from the K plate of a CMYK version, brought it into the master RGB file and colorized it as green to show where the second hit of shadow would fall.

[BillA]

The car itself it red. The green is the darkest shadows. Showing a film positive is a habit from working with screen printing (light exposure hardens the screen emulsion, the unexposed area washes away allowing ink to pass through).

Here's the example reversed out in proper form. The original image can be found here.

I also wonder if the Photoshop calculations option might not help you make the mask you want.

[bob carnie]

This looks like what I am trying to achieve.
It should be noted that I would be working from black white files and not going directly from the colour file.
Working from the K seems to be the way to go right now , I am investigating a bunch of other methods and will report back my thoughts.

The car itself it red. The green is the darkest shadows. Showing a film positive is a habit from working with screen printing (light exposure hardens the screen emulsion, the unexposed area washes away allowing ink to pass through).

Here's the example reversed out in proper form. The original image can be found here.

I also wonder if the Photoshop calculations option might not help you make the mask you want.

[Tyler Boley]

why complicate things? You can do exactly that and most options discussed so far with a curve, the beauty of which you can make and tweak exactly to your particular needs.
What am I missing?
Tyler

[bob carnie]

Tyler

I am not doing any thing new here, Irving Penns prints were done with multiple hit exposures using different negative, many artists use different negs from different channels to make multiple hit images.
I want to separate the image into three distinct negatives for multiple printing.

What don't you get about that?

Bob

why complicate things? You can do exactly that and most options discussed so far with a curve, the beauty of which you can make and tweak exactly to your particular needs.
What am I missing?
Tyler

[Tyler Boley]

I know exactly what you are trying to do, and certainly aware of the Penn prints and other processes mentioned.

But why not run any curve on it you like to get your desired black kicker and save as such. Same with any tonal area you want a separation for.
The various conversions to CMYK then save the K are more complex than necessary, and the K generated dependent on the particular CMYK converted to, and not necessarily ideal for you particular need... any other suggestion so far can also easily be done with a curve...

OK then... never mind.
T

[bob carnie]

Tyler

Yes
running a curve will work as you point out. Put a sample point on a shadow area, run a curve to make a selection as you point out , then read the before and after numbers and you will find that they dramatically change.
I do not want the more dramatic curve shape of this method, I want to maintain the same shadow detail number, as well as the same highlight detail number. The second hits are only for process problems , not the inability of recording this info on the film.
The point of all this is to compensate for physical process problems, carbons highlights are difficult to maintain due to the wash off process,
and Platinum d max can be increased with a second shadow hit, I don't want to change the contrast, but only put down more tones in these two problem areas.

maybe this makes more sense now?