Creating Custom Alpha Channels for Digital Neg Output

[RDWestPR]

Hi all, I’m trying to get a fix on software that will let me directly edit, add or delete alpha channels before conversion and output to digital negatives. I’ve used Photoshop since v2.5, my last version was Photoshop Creative Suite 5.5 (before they went to subscription only). I’ve been using Affinity Photo for general editing and composite work, but it only allows you to edit layers, not alpha channels. Some of the Silkscreen spot-color color sep software will do what I’m looking for, but it’s almost as expensive as Adobe’s stuff. The aim is to produce simple 2 and 3 color, spot color duotones using the Carbon Transfer process. I’m not looking to do CMY/K. Am I stuck getting a subscription to Photoshop or is there an alternative? Any thoughts on this will be much appreciated. Oh, I’m on a 27” iMac, if that matters. Thanks, Rob

 

[Pieter12]

Adobe has short-term subscriptions (for business, but I don't know how they determine that) if this is not for an ongoing project. Also, I assume you no longer have PS 5.5? CS6 runs fine with the Mac OS 10.14.

 

[nmp]

Hi all, I’m trying to get a fix on software that will let me directly edit, add or delete alpha channels before conversion and output to digital negatives. I’ve used Photoshop since v2.5, my last version was Photoshop Creative Suite 5.5 (before they went to subscription only). I’ve been using Affinity Photo for general editing and composite work, but it only allows you to edit layers, not alpha channels. Some of the Silkscreen spot-color color sep software will do what I’m looking for, but it’s almost as expensive as Adobe’s stuff. The aim is to produce simple 2 and 3 color, spot color duotones using the Carbon Transfer process. I’m not looking to do CMY/K. Am I stuck getting a subscription to Photoshop or is there an alternative? Any thoughts on this will be much appreciated. Oh, I’m on a 27” iMac, if that matters. Thanks, Rob

You can zero out the complementary channels to get the channel of interest. For example, if you need the red channel, bring 255 to 0 in Curves (I am assuming there is something similar to Photoshop Curves in Affinity) for both green and blue channels and you are left with the red values of the document.

(If I understand your problem correctly...)

 

[jim10219]

I'm not sure about Affinity, but PS has (and has had for quite some time) a color range selection tool that allows you to select everything on the page within a color range. You can then copy and past that to a new layer. With some careful editing and experience, you can make color separations for just about any color scheme you want. This is what a lot of the better prepress people do in the t-shirt industry. The automated software you see, like T-Seps, Spot Process Separation Studio, and UltraSeps are mostly used by smaller companies that can't afford to hire a dedicated professional who really knows what they're doing. Those software programs work okay for basic work, but if you really want to take control and do high quality separations, you'll need to do them by hand.

There are also some other methods of doing separations by hand. I'm not familiar with them all, but there are videos and instructions online if you look up "photoshop spot color separations" or similar.

If you're just wanting to do duotone or tritone, then that would be pretty easy to do with the color range selection tool. If you were looking to do something more complicated like CMYKOGV printing, that would be really difficult to pull off.

 

[Dan Pavel]

In my opinion the best way to do it in PS is to use Image ->Mode -> Multichannel. I am using it to make DNs for color gum prints in CS6. You can edit channels separately (but with a reduced set of tools) and then separate them into different files to print the DNs for each channel. You can choose the color of each channel as you wish (to match the colors of your Carbon Transfer Layers) , delete or add new channels.
A trick - to preview the channels, one by one, in their real color you have to add an white empty channel and preview each channel together with the white one.
For better results start with the CMYK mode and then change it to Multichannel. RGB > Multichannel doesn't produce very accurate colors. If you start with a RGB image then transfer it first in CMYK and then in Multichannel. After changing mode to Multichannel the colors may not look accurate but after some Levels, Curves and Brightness/Contrast adjustments applied on each channel separately you can make them look quite accurate.

 

[RDWestPR]

Thanks everyone, for your responses. I will be adopting several of the suggestions. I did go ahead and score the monthly deal on Photoshop. It is the only way I can formally access the 'classic' duotone process. At some point I'll share how I made it work.