Better 2-spot + white images than duotone?

[nickp81819167]

I'm printing a conference program booklet using two Pantone colors (295 - Navy Blue and 200 - Crimson).

When converting RGB/CMYK images, I can easily make grayscale versions and color them InDesign, and I know how to create duotones from those grayscale versions - but the duotone version basically just looks like a purple-y grayscale image.

Is there a way to get a better looking 2 spot + white version of an image? I worry that by converting to grayscale first I lose all the color nuance of my image.

What am I missing?

[Stephen_A_Marsh]

Sure there is a “better way” than just a standard Photoshop duotone… these were sometimes referred to as “extended duotones” by some folk. Similar to “spot colorisation” in many ways, except automated and using tones and not just solids.

However this is very much image dependent, do you have a random sampling of images that you can use as examples? For example, if there were warm hues in the full colour original, they could be used as the Pantone 200…but what if there were cool hues, should they be removed or merged into the Pantone 295 hues?

Off the top of my head I can come up with at least three different general ways of doing this, however best results depend on the method being tailored to the images.

For example, the actions are still available from this topic:

Re: converting CMYK image to multichannel (black + one spot color)

[nickp81819167]

These are all headshots, so they're mostly fleshtones, with hair and some background.

I tried your first suggestion in the other thread (used the yellow channel for the red pantone and the black channel for the navy pantone) and that's MUCH better. I assume that if I delete the CMYK channels I can save that file as a PSD, place it in InDesign and all should be well for printing?

I'm off to try that other process, it looks like it'll take some time.

I've attached a few examples so you can see if there's a better way.

[Stephen_A_Marsh]

Thanks, I’ll get back to you…

If there are any privacy concerns, you can now remove the images (I have a copy and will tailor the action around them).

P.S. As a general rule for skintones, you are better off using the G channel of RGB or the M channel of CMYK as this will generally have less compression artifacts than the blue or yellow channels.

[Stephen_A_Marsh]

Here is an example.

Top row the RGB originals, converted to CMYK as a start point before an automated action was run.

Bottom row the 2 multichannel/plate versions, blue 295 and red 200, in an empty/blank grayscale file.

They may or may not print ANYTHING like the onscreen preview though, I would strongly advise a proof from a provider that stands behind their proofing method! The overprinting and preview of spot inks is technically very difficult, most Pantone inks are designed to be printed solid and in isolation, not screened and trapping/overprinting another spot colour in order to make another colour.

[Stephen_A_Marsh]

A couple of inkjet proofs from two different prepress proofing RIPs… Both uncalibrated, so only general rendering, not colour accurate (not to mention scan and photo rendering, colour management etc). Top photos taken under two different light sources, then white balanced. Bottom, cheap scanner:

As you can see, a lot of colour/tonal variation… and this is not even printed on a press yet, just inkjet and different acquisition methods!

Again, what the final colour will be is anyones guess and it will pay to look at the % values of each colour and try to imagine how these will combine. My guess is that the top image which is more biased to pink than to yellow would be closer to a final spot colour print run.

[Stephen_A_Marsh]

Here is the action that created the above images (it has had some minor tweaks since then, as this is a copy of another more generic  action that has been a stalled work in progress).

Dropbox - Extended Duotone.atn.zip

Input is RGB, run the first action titled “Extended Duotone: Black & Red” which will create a generic grayscale and spot red conversion… There are a few “stops” added with/without instructions so that you can make creative decisions at key points.

After the first action has finally completed and you are happy, then run the second action titled “K=295 R=200” which should convert to a multi-channel file with the Grayscale changed to PANTONE 295 C and the generic spot red changed to PANTONE 200 C.

Please note that the red spot channel may show severe blocking artifacts if the source images have had JPEG compression applied to them. You may wish to make individual edits to each photo to tidy up the blue or red channel. Save the mutli-channel mode file as either PSD or EPS DCS2 for use in page layout software.

Use at your own risk, no warranty or guarantee is provided, nor should it be assumed that the action creates a file that is fit for any final printed purpose! Get the idea? :]

P.S. If you DO use the action, I would really appreciate it if you updated this topic with photos of the final printed piece so that I can see how things turned out. 

[Stephen_A_Marsh]

And another action, this time a bit simpler, leveraging the legacy Custom CMYK engine to create a Max K GCR file and then using the M and K plates.

Dropbox - Extended Duotone v2.atn.zip

[Norman Sanders]

You may use Photoshop's Duotone option to create the duotone using your two chosen colors and have control the tonal scale and prominence of each color by adjusting the slope in the grid alongside the color patch in the Duotone drop-down panel.

Note that the Channels panel shows the duotone as a single channel. To save the file with each spot color's tonal scale adjustment as a separate channel, follow these steps to

1. Image > Mode > Multichannel (Note the two channels in the Channel panel.)

2. File > Save as…  In the Format field choose Photoshop DCS 2.0

[Stephen_A_Marsh]

That is a great image Norman, with both warm and cool hues, the question that I posed in my original post regarding what happens to warm hues that share the same tonal range as cool hues… Do we want a warm object going cool, or muddy – or “pure”? Here is the same image treated with the “extended duotone” method:

[Norman Sanders]

Thanks, Stephen, but I don't want to mislead you. I don't recall where I found it but the image is one of a large group that I used in my Digital Darkroom course for many years.