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bkliche
10-23-2012, 10:25 AM
Dear all,

my problem is the following:

a printed rgb pdf ripped on the fiery does never match the same pdf converted to cmyk by software (pit stop). i use the same settings for both procedures (same source and output icc profile, same rendering intent) and when printing the software converted pdf i also switch off cmyk simulation (Profile "none"). i have also tried to use the fiery output icc profile to convert the rgb file in pitstop.

I have to say that most files we print are originally powerpoint files converted to pdf but i think that should not matter in this case as the pdf conversion is correct, no Color managent is applied while distilling etc.

The background is that we often have to convert the powerpoint pdf files to cmyk to be able to make changes to this loosy powerpoint crap to get it printed right (we have to change grey Text to real cmyk grey before sending it to the fiery etc).

another question is: which icc profile should be used for converting office files to cmyk. which rendering intent? i think Srgb source, iso coated v2 Simulation and presentation rendering intent would be right. but surprisingly setting a wrong source Profile (ie. eci-rgb) and an different rendering intent (relative colorimetric) do often give us better results. why is that? and how can i manage to get nearly the same results by Rip color conversion and Software color conversion?

greets from Hamburg,

Benjamin

Lou_P
10-23-2012, 02:57 PM
Benjamin:

Setting CMYK input profile = None turns off color management for CMYK on the Fiery. So whatever CMYK values you send "just print", kind of like making plates for a conventional press.

So if you convert colors in PitStop using say sRGB source and ISO Coated v.2 output and send this to Fiery, you need to set the source CMYK to match the profile you converted to, ISOv.2. Now the Fiery will convert from ISO v.2 to the Fiery output profile. Use the CMYK setting "Full (Output) GCR" for the best precision, this uses the relative colormetric intent which is fine for CMYK to CMYK.

For the RGB to CMYK in Pitstop I would use the saturation rendering inent if you want saturated colors or the Relative Colorimetric intent if the PPT has images and you want them to look natural not oversaturated.

One more choice would be to have the Fiery do it all: set RGB source to sRGB, intent to Presentation, source CMYK to ISO coated, then turn on "Separate RGB.LAB to CMYK Source" in the expert color settings. This will cause the Fiery to convert rgb source data in the PPT from sRGB to the ISO v.2 profile using the saturation intent then the ISO v.2 data tot the Fiery output profile using the Relative colorimetric intent. This should closely match the PitStop conversion and so has the advantage of efficiency but the disadvantage that don;t get to have a CMYK verion on your workstation if you need to adjust it manually. You could adjust in Fiery Image Viewer on the Fiery if you have the Graphic Arts Package Premium Edition.

Hope this helps.

~Lou

bkliche
10-24-2012, 01:40 AM
Benjamin:

Setting CMYK input profile = None turns off color management for CMYK on the Fiery. So whatever CMYK values you send "just print", kind of like making plates for a conventional press.

So if you convert colors in PitStop using say sRGB source and ISO Coated v.2 output and send this to Fiery, you need to set the source CMYK to match the profile you converted to, ISOv.2. Now the Fiery will convert from ISO v.2 to the Fiery output profile. Use the CMYK setting "Full (Output) GCR" for the best precision, this uses the relative colormetric intent which is fine for CMYK to CMYK.

I thought it would not be necessary to simulate the cmyk icc profile if the source file already has the same cmyk icc profile that has to be simulated? is that wrong?



For the RGB to CMYK in Pitstop I would use the saturation rendering inent if you want saturated colors or the Relative Colorimetric intent if the PPT has images and you want them to look natural not oversaturated.

No matter which icc profiles i use for conversion, there is always a drift into magenta. We have many blue gradients in the rgb-files we have to print/convert, and the blue gradients always get purple in software conversion as well as rip conversion. Do you have an idea what to do? I Think it's not a matter of calibration as it is performed regularly and software conversion drifts into magenta, too.




One more choice would be to have the Fiery do it all: set RGB source to sRGB, intent to Presentation, source CMYK to ISO coated, then turn on "Separate RGB.LAB to CMYK Source" in the expert color settings. This will cause the Fiery to convert rgb source data in the PPT from sRGB to the ISO v.2 profile using the saturation intent then the ISO v.2 data tot the Fiery output profile using the Relative colorimetric intent. This should closely match the PitStop conversion and so has the advantage of efficiency but the disadvantage that don;t get to have a CMYK verion on your workstation if you need to adjust it manually. You could adjust in Fiery Image Viewer on the Fiery if you have the Graphic Arts Package Premium Edition.

Yes, the RIP conversion is always best. But that doesn't solve our problem. We need to have a RIP conversion that meets the software conversion performed with pit stop. How about using the fiery output profile for software conversion and as rip simulation profile in CSW, would this make sense? I have just tried it and results are not perfect, but better than i.e. iso_coatedv2 and other standartized icc profiles.

bkliche
10-24-2012, 06:50 AM
No matter which icc profiles i use for conversion, there is always a drift into magenta. We have many blue gradients in the rgb-files we have to print/convert, and the blue gradients always get purple in software conversion as well as rip conversion. Do you have an idea what to do? I Think it's not a matter of calibration as it is performed regularly and software conversion drifts into magenta, too.


OK, i have found a solution to this problem. The Fiery Color Ref says that SRGB should never be used for converting Office RGB Files to CMYK. They suggest using Fiery RGB or ECI RGB. This does really give much better results and eliminates the problem with blue turning to purple. But i still don't understand why converting a PDF file on the rip does not match converting pdf file external to the rip by eg. pitstop with exactly the same parameters. Have i disregarded any settings when printing the already converted cmyk pdf via cws? The color mismatch can already be seen in the preview after the files have been ripped on the fiery.

bkliche
10-30-2012, 12:08 AM
Does nobody have an idea what to do?

Lou_P
10-30-2012, 12:12 PM
There may be some differences based on the CMM used. Let me clarify what you are asking: if you use a special profile like Fiery RGB to solve the blues-turn-purple problem it works on the Fiery but not in Pitstop? What rendering intents are you choosing in each case? And please confirm you are converting to the Fiery output profile in Pitstop or to ISO in Pitstop and setting Fiery CMYK Simulation to ISO then choosing "Separate RGB/LAB" option in Fiery expert color settings.

~Lou