RGB to CMYKOVG Profile Conversion

[Bill W]

Greetings,

Need suggestions on what plug ins can be added to Photoshop that will allow me to convert from an RGB image to my 7 color HP profile (CMYKOVG).

I need to do this conversion before I submit an file to our HP 6600 via an Esko created Color Strategy.

-Bill-

 

[DavidH]

Hi Bill,

Esko has a Photoshop plugin called "Equinox" that does exactly this. It will work with the Esko CMYKOVG press profiles that you are already using in the 6600 DFE.

David

 

[Schnitzel]

Photoshop CS6 has a conversion to multichannel profiles built in, via the "Convert to Profile" menu.

 

[rich apollo]

Hey, Bill. Photoshop has supported multi-channel profiles since CS2. If you have a profile, you should be good to go.

The downside is that you will not be able to use the resulting image anywhere else in the Creative Suite. However, I have a work-around that I will share for obscene amounts of money and praise.

 

[Stephen Marsh]

Hey, Bill. Photoshop has supported multi-channel profiles since CS2. If you have a profile, you should be good to go.

The downside is that you will not be able to use the resulting image anywhere else in the Creative Suite. However, I have a work-around that I will share for obscene amounts of money and praise.

Would you settle for just praise Rich? ;]


Stephen Marsh

 

[rich apollo]

Okay, Stephen. You're very persuasive.

Convert to the multi-channel profile. What you'll get is not CMYK+, but a multichannel file - kinda' like the old DCS days (each channel is more or less its own file). Then, go File>Mode>CMYK (just like you're never, ever supposed to). Now you end up with CMYK+. This operation, somehow, maintains the file values and just stitches the channels back together. You can't tag the resulting file correctly in any Creative Suite application, but...

 

[Bill W]

However, I have a work-around that I will share for obscene amounts of money and praise.

Thanks for the information. Working this weekend on the finishing touches to my shrine to you that I started after our first meeting years ago in Phoenix. I have entitled it the nice, smart guy shrine. I hope that will do for praise. About the money - still collecting the road side aluminum cans - get back to you soon.

I had tried a multi channel conversion in Photoshop but the preview looked weird. Your trick not only appears to correct the weird looking preview, but edits out Hexachrome in the CMYK channels which means less color mapping in my HP color strategies.

Next week I will see if I can sneak a few conversions into the press schedule for a "proof in the pudding" view.

 

[rich apollo]

yeah, I can see where the previewing would be strange. I believe you can control the naming of the channels during the creation of the multi-channel profile - I'll have to do some experimentation on that.

Let me know how the press testing goes, would you?

By the way, Bill, "WASABI!!!"

 

[Bill W]

Rich, yes one can control the naming of the channels in Profile Maker when making a multi-channel profile, as I found out this morning. I tried to check a pixel value between my original image in RGB and my converted to cmykogv version of that image. Before I used your trick the pixel I checked did not report Lab values in the cmykogv version, only the L value. Using your trick allows Lab values to be expressed. Here are the values I measured in the original rgb file, the file converted to Gracol 2006 and the file converted to my cmykogv profile:

rgb
L=66
a=72
b=11

Gracol
L=58
a=63
b=5

My cmykogv
L=58
a=64
b=-3

I would of thought that a 7 color conversion would be closer than a 4 color conversion. Maybe, like the preview not looking correct, Photoshop cannot accurately report the Lab of a multi-channel profile.

And yes Rich, more wasabi is always the order of the day.

 

[Stephen Marsh]

Thank you for sharing Rich. I have been unable to play with this as the two multichannel profiles that I have at hand do not seem to work in Photoshop.


Stephen Marsh

 

[rich apollo]

I would not expect Photoshop to give accurate Lab values under these circumstances. The CMYK color space you're assigning is not accurate. To make productive use of multi-channel profiles, you'll have to take the work outside of the Adobe apps, and into a file format other than PDF.

I hear that Quark (remember them) can handle multi-channel files. This is an area where PostScript would/will allow what PDF won't.

 

[buckeye]

I hear that Quark (remember them) can handle multi-channel files. This is an area where PostScript would/will allow what PDF won't.

But only saved as a PSD file, correct? EPS, PDF or placed TIFF files from Photoshop will convert the 5th channel to cmyk, in my experience.

-Erik