black not knocking out - indesign

[wonderings]

Having an issue with indesign CS6, not sure why its doing this it would normally work fine in the past. Black is set to knock out, not to over print on top of other colours.


This is an example of what I mean. There would be a black bar across an image:


When it comes to making plates for press we want the background image knocked out. It looks as it should in separations in indesign:


I print the file as a CMYK file:


And when it gets to our rip, I look at the separations and the black is not knocking out the background image. I think it has to be something on the adobe side rather then the rip as we don't change any settings on our rip and this use to not be an issue, things just worked fine.

Any idea what is going on here? Am I missing one small little thing for this to automatically happen?

[Stephen Marsh]

As this is a composite colour print (not separations), I would double check the RIP for overprint settings, which are very common to be defaulted for 100% K to overprint and for CMYK White to Knockout. Be wary of turning off black overprint at the RIP, as you may find that all small elements such as text and rules/lines may knockout.

Try printing to .ps file with your standard composite settings and then use Distiller to create a PDF. Then open the PDF in Acrobat Pro and use the output preview to see what is taking place in the file. If the panel knocks out, then your RIP is overprinting.

Try sending separations from the InDesign print command (these will honour the InDesign colour settings and bypass the RIP overprint settings). Again be careful of black text/rules that should overprint!

When I send work out to printers as composite CMYK PDF files, I place a white box under such a large black panel - to help ensure that their default RIP settings are not going to screw up my file if I do not wish overprinting to take place (I manually choke the white panel slightly smaller to form a trap and then set the K box to overprint). I doubt that the panel in your screen shot is trapping to the image and may cause fit issues on press.


Stephen Marsh

[wonderings]

As this is a composite colour print (not separations), I would double check the RIP for overprint settings, which are very common to be defaulted for 100% K to overprint and for CMYK White to Knockout. Be wary of turning off black overprint at the RIP, as you may find that all small elements such as text and rules/lines may knockout.

Try printing to .ps file with your standard composite settings and then use Distiller to create a PDF. Then open the PDF in Acrobat Pro and use the output preview to see what is taking place in the file. If the panel knocks out, then your RIP is overprinting.

Try sending separations from the InDesign print command (these will honour the InDesign colour settings and bypass the RIP overprint settings). Again be careful of black text/rules that should overprint!

When I send work out to printers as composite CMYK PDF files, I place a white box under such a large black panel - to help ensure that their default RIP settings are not going to screw up my file if I do not wish overprinting to take place (I manually choke the white panel slightly smaller to form a trap and then set the K box to overprint). I doubt that the panel in your screen shot is trapping to the image and may cause fit issues on press.


Stephen Marsh

Thanks for the reply and you did point out what I was doing different. I sent composite cmyk rather then separations which I normally do. Sending separations indeed gives me the desired result, not sure how that completely slipped my mind, I do it enough.

Thanks again for the help, much appreciated!