Colorized Bitmaps, with a manual trap knocking out

amybest222

Well-known member
I have a book, sent to a printer with will 100% black ( colorized bitmap @ 1200dpi ) with a manual trap created in photoshop. (1 pixel) The trap was created (an illustration outline) and is placed on top of a grayscale psd., colorized in a Pantone 149U. A 2 color book.So I have black image (bitmap) manually trapped to a CT image. Clearly the image when previewed in overprint preview, reflects the bitmap (trapped manually) is actaully KO of the underlying pantone.
When this printed it is clearly out of registration. Clearly this is not a RIP issue, because the document in INDD and Acrobat is clearly knocking out? My question is how do I get the bitmaps to trap and not knock out without applying a multiply effect? #publishingproblems ( Prinergy 7.5) and in Acrobat X and Indd CS2015.5
 

gordo

Well-known member
I have a book, sent to a printer with will 100% black ( colorized bitmap @ 1200dpi ) with a manual trap created in photoshop. (1 pixel) The trap was created (an illustration outline) and is placed on top of a grayscale psd., colorized in a Pantone 149U. A 2 color book.So I have black image (bitmap) manually trapped to a CT image. Clearly the image when previewed in overprint preview, reflects the bitmap (trapped manually) is actaully KO of the underlying pantone.
When this printed it is clearly out of registration. Clearly this is not a RIP issue, because the document in INDD and Acrobat is clearly knocking out? My question is how do I get the bitmaps to trap and not knock out without applying a multiply effect? #publishingproblems ( Prinergy 7.5) and in Acrobat X and Indd CS2015.5

An easy way is to take each channel (the greyscale and the bitmap) and place them in a cmyk image. I.e. one image is in the C channel and the other in the M channel with the Y and K being empty. It will look weird but it will give you the two correct plates you need which will be printed in the appropriate colors on press.
 

DCurry

Well-known member
Gordo, won't the differing resolutions present a problem with your scenario? I am assuming that the grayscale PSD is likely not 1200ppi like the bitmap, so either the bitmap would have to be downsampled to match the PSD or the PSD would need to be upsampled to match the bitmap.

Amybest222, I'm with Priceline on this one - why are you pre-trapping your own files? This is definitely not the norm. However, if you insist on trapping this manually yourself, you could set the bitmap image to Overprint. This will have the same effect as Multiply, but it will maintain each image's respective resolution.

I see that either you or your printer is using Prinergy - best to let Prinergy handle the trapping - it will do a better job and be far easier, even if you have to tweak a couple settings to achieve the desired result.
 

amybest222

Well-known member
Thank you Gordo for your work around, this is the entire scenario. Publishing trade. Files (illustrations) outlines have always been created as Bitmap images and "spread" to help the trap with the underlying spot color. In this case also a CT. My manager comes to me and says " look at this printing....." (done at an outside vendor). It is clearly out of registration. The colorized (with black) bitmap knocks out.,As it is represented in both Indd and Acrobat overprint preview. My question is, with out setting the bitmap to overprint or multiply, how do I ensure that the Vendor traps CT to CT, black to spot color. Even by default when colorized with another Pantone Black it still KO. Im trying to insure trapping between the 2 colors. Am I correct in saying that this solution should be done in the RIP? As a prepress operator, If Im ripping and I'm imposing a 2/c job, Im previewing and evaluating the ripped file.
 

amybest222

Well-known member
[USER][/USER] We are not necessarily "trapping our files" but trying to add an overlay ("spread") between the two colors to help ensure registration. This is the file prep procedure that has been in place before I was working here. The Bitmaps are 1200 dpi and the psd are 300 dpi. Just trying to ensure the registration when printing. Looking for suggestions.
 

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DCurry

Well-known member
I would leave the trapping to the vendor, but ask for a way to view the result in the proof. Since the vendor is using Prinergy, see if they also are using InSite which will let you view ripped files in all of their trapped glory, then you can approve or reject on a page-by-page basis. It lets you view separations to make it easy to check traps. Don't approve the job until you are satisfied with the proofs and that trapping has been applied to your liking.

If they don't have that feature of Prinergy, see if they can provide you with a PDF proof that shows trapping. The best bet would be a PDF proof that has been rasterized by Prinergy - this will assure that the same engine that rasterizes for plates did the rasterization of your proof.

It also wouldn't hurt to include a line in your PO or quote request that states "vendor is responsible to apply all trapping."
 

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