PDF transparency settings

Macmann

Well-known member
We recently took delivery of an HP R1000 wide-format latex printer. It has an Onyx front end with the ability to lay down a flood or select white. The tech told us to set the spot white to overprint and to "never use multiply or transparency... transparency causes problems" This seems like old fashioned thinking to me. Does this mean I have to check entire customer supplied files for instances of transparency blend modes. This seems so 1999 to me? Thoughts?
 
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dpierce@packgraph.com

Well-known member
Macmann, transparency did not exist in 1999 - but I get your point. Your HP guy has probably grown accustomed to inexperienced or inept users encountering RIP systems or the ability to print white ink where that experience is absent. Did you ask him why? His comments were probably made specifically in reference to the introduction of the opaque white elements of the art. If objects colored Opaque White are being placed on top of the art that will get the white base and those OW objects are set to Multiply, they will indeed multiply and you won't get the results typically expected - a white base on which the other color inks print on top of. Using Darken will act most like Overprint and I am not aware of a problem with that.
He is using the K.I.S.S. principle. If the artwork is layered this way, with OW objects at top level and made to overprint, transparency effects elsewhere in the art should not be a problem.
Macmann, best of luck with the new capabilities and opportunities that come with it.
-dan
 

Macmann

Well-known member
Thanks Dan-pretty much what I expected. Just curious though, We've used Multiply with spot colors for years without an issue-what problems were you speaking of? Is this specific to OW?
-Macmann
 

dpierce@packgraph.com

Well-known member
I have seen odd results when spot colors have been treated with Multiply over process (images) where the CMYK values changed but this may be/have been rip specific. With pdfs and overprint preview I have been pokiing around with in the last half hour, I didn't see any negative effects with Multiply with spot colors.
-dan
 

Seeking Knowledge

Well-known member
Macmann, I think your HP tech was saying do not use multiply or transparency with white, specifically. It will be hard to predict the outcome when using those effects. I also would make the suggestion to not let your customers build white for you. This can lead to headaches, trying to understand that the are looking for. Unless it is a simple flood of white of course. But when is printing ever that simple.

SK
 

Philo

New member
In any case, the combination of Multiply and overprinting on an object must absolutely be prohibited. This has the effect of creating an involuntary ghost image in the background.
 

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