Pitstop 2017

[abc]

I'll put you down on the list for the next one...

[Tracy]

I think ABC may be the only one that can answer this question.

When I use the reduce Ink Action, I have been compressing jpg compress to Zip compress 1st
altho I do not see any quality reduction when using the action on the jpg compressed images

Is it safe to use the Reduce Ink Action on jpg compressed images?

also I notice a color change when changing non device cmyk to device cmyk
usually on bad files, which is fine, worst case I can adjust in photoshop, but would like to know why this happens and
the proper way to change to device cmyk

[mattbeals]

The images are decompressed to be converted, then recompressed back to JPEG. You could change the JPEG quality level, but that will toss bits again. I make the conversion to ZIP/Flate compression one of the first tasks as part of the preflight process. So it's not a problem to use the device links to reduce the ink in JPEG's.

Changing from RGB or spot colors to CMYK is always a bit of a sticky topic. You first must know where your color is originating. Having objects tagged with ICC profiles helps the CMS to know what color space to map from correctly into the destination space. If the objects are not tagged then PitStop has to assume a color space. That happens in the color management settings in the PitStop preferences. The profiles there are only used when an object is not tagged. Then in PitStop you also have to set the destination space.

If your PDF originated from Word or the images from a digital camera, then it's pretty safe to assume in PitStop's preferences that sRGB is the source RGB space. If you have a Nikon digital camera there is a specific Nikon RGB profile for some models. Adobe RGB might sound like the best source space to use, but it likely is not.

Once you know what source space you have, what destination space you want to go to, you then must pick the rendering intent. For lack of a better term, the source color space (tagged or assumed) is your home address, the CMYK space is your destination, and the CMS engine and the rendering intent provide the directions.  Most of the time relative will work well for RGB to CMYK. But there are reasons to use perceptual for line art and/or images.

Set your Acrobat Pro color management to the right settings, then match them in PitStop (or vice versa) and know what profiles to use when and it will be far easier. I set my Acrobat Pro preferences to sRGB and FOGRA39/Gracol 2006. I set my PitStop preferences to
Source Grey: Dotgain 20%
Source RGB: sRGB
Source CMYK: FOGRA39/Gracol 2006

Destination grey: Fogra39/Gracol grey (extracted black channel from the FOGRA39/Gracol profile)
Desitination RGB: ECI RGB
Destination CMYK: Fogra39/Gracol 2006

Rendering intent for images: Perceptual
Rendering intent for other objects: Relative

Generally works out quite well for me. I also have specific device links with ink limiting and GCR build for sRGB to Gracol/FOGRA39 and a number of other scenarios where I can go direct to CMYK in one process rather than RGB-->CMYK--> Ink reduction with device link. I can use a device link to go RGB-->"optimized" CMYK. You can do if you have such profiles and properly configure your color management.

Don't forget that you can in action lists or preflight profiles override color management settings so that you can create actions/profiles/processes (even using design layout) to process particular PDF's in particular ways without having to change your Acrobat and PitStop global preferences.

Similar things can be done with PitStop Server, Connect You, Connect all, Switch, etc. if you think through the process first.

[Tracy]

Thanks Matt!
I actually kind of understand what you said!