Overprinting Agfa Harlequin RIP

[Master468]

Dear All,

in the moment verifying our prepress workflow. Amongst others the overprinting behaviour. When using one of the common testforms (e.g. from Ghent group) and simply converting the green spotcolor to CMYK (via alternative color definition) the now CMYK-CMYK overprint (overprint=yes, OPM=1) leads to a knockout, which, given the actual channel values, is perfectly right (see first picture). When ripping the original file (with spot color still present) and omitting any separate spot color plate, thus converting by the RIP in the same way, there is still overprinting (see second picture, constructed from the TIFF/G4 files). Am I missing something or is this supposed to happen - although it internally is converted to CMYK?

 

[Master468]

no one an idea?

 

[maxon]

To begin with you might want to determine if that test file is supposed to be processed correctly on your RIP which I assume it's an ancient PS level 2 harlequin version.

 

[michaelejahn]

in the moment verifying our prepress workflow. Amongst others the overprinting behaviour. When using one of the common testforms (e.g. from Ghent group) and simply converting the green spotcolor to CMYK (via alternative color definition) the now CMYK-CMYK overprint (overprint=yes, OPM=1) leads to a knockout,

yes, if you start with a spot color and convert that to CMYK, of COURSE C,M,Y and K would overprint !

which, given the actual channel values, is perfectly right (see first picture).

Yes, glad you understand that ...

When ripping the original file (with spot color still present) and omitting any separate spot color plate, thus converting by the RIP in the same way, there is still overprinting (see second picture, constructed from the TIFF/G4 files).

Yes, if the spot color is set to overprint, that would meant that plate is solid - and to "view" that you would need some method to "simulate" that on screen - as you could imagine, if you had a spot yellow color overprinting a 100% black - it would simply "look" blacker.

Am I missing something or is this supposed to happen - although it internally is converted to CMYK?

I must say, the very FIRST thing i was confused by is that you wrote "AGFA Harleguin Rip" - as someone who worked for AGFA, we either made our own RIP ( I think that was only used to drive the Chromapress ) - but - by far more frequenly - AGFA licence the Adobe CPSI RIP, the Adobe Extreme RIP, the Adobe PDF Engine or Adobe Mercury.

I have never heard of an AGFA Harlequin RIP

But if you DO have a Harelquin RIP, you would need some other software to preview the post RIP tiff files.

I think Xitron offers a tell that allows you to "preview" the TIFF files.

http://www.xitron.com/files/4415/0764/3203/Navigator_Harlequin_RIP_Borchure_digital.pdf

 

[Master468]

Many thanks for your answers so far. Sorry for the uncomplete RIP info. Our RIPs in the different print houses are all Agfa Arkitex RIP X ones (based on Harlequin MultiRIP 10.1 Revision 1), without ColorPro. Jobs are usually normalized* prior arriving at the RIP (OI is for Newspaper printing), with flattened transparencies. No spot colors. So a very controlled and limited environment, my checks are just to know where we stand. There are a few other "weird" things like overprinting behaviour with DeviceGray (see the color setup picture which should lead, in contrast to default behaviour of no overprint, to no knockout on CMY for images, but there is knockout as soon as an output intent is present in the file). But let's concentrate on the spot color thing first. I also attached the separations (scaled down from the original TIFF/G4 bitmaps created by the RIP). My picture in the first post was also based on these separations.

*The test files though I have directly sent to the RIP, avoiding any changes during our color server processing.

I think Xitron offers a tell that allows you to "preview" the TIFF files.

Sorry, I maybe have described it not so precisely. The second image in my first post "Spot to CMYK RIP" was already created by the actual bitmaps that were output. Just scaled and smoothened.

Best regards
Denis

 

[Master468]

Here the separations (scaled down so raster is distorted but it can be seen quite good that it outputs 100% Yellow and 50% Cyan (disabled any linearization and process calibration), according to the alternate CMYK definition of the green spot color, and there is no sign of the "X" which has minimal channel value in Yellow and Cyan and lies above the former spot color. The behaviour is just as if the "X" would have 0 in every channel. But as you can see in the PDF, Cyan is 0,5% and Yellow 1%, at least when entering the RIP.

 

[Master468]

An update. The PDF/X4 testforms from Ghent Group have some additional transparency groups, besides the pages where actual transparency handling is tested. For the header (drop shadow) and the mask => OK. And there are no other affected objects. The inspector and preflight show non knockout subgroups for every object. Should do nothing but in fact when present, the above described behaviour arises. When I remove these groups, everything is as expected. So in the end still the question why the RIP behaves in that way when overprinting objects are encapsulated in non knockout transparency groups with no transparency effect enabled.