How do I "fix" maximum ink density

Question

I'm working with a printer who requires a maximum ink density of 240%. They've just kicked back a file with deep purple hues, with the explanation that it's "difficult" to keep a cover like this within that range.
What tools or windows do I look at in Photoshop to see where the problem areas are, or what other steps do I need to take as I attempt to revise this file to their standard? (In other words, I can't have the purples I want, but I'd like to change them only as much as needed. How can I know what I'm doing so that they won't kick back the file again, and charge me for another proof?) Sigh.

Answer 1

Sorry, heres the full explanation (hopefully maybe others will chime in if ive missed anything)-
As Buko suggested in his first post ....you can change your Color settings to a Custom CMYK  (edit/color settings - permanent in Photoshop until you reset them )- this custom cmyk will allow you to specify a "maximum Ink". Then just converting to Cmyk any time Image/mode/CMYK - will convert using the setting you have created. In your case provided you chose  "Total Ink limit" 240% - It will not generate CMYK separations, where the total ink exceeds 240%
One problem with this -  you have to remember that its set this way, so that it can be set back to something more sensible as your default. On some presses a total ink of 240 will look very washed out, and flat. So alternatively you can also convert using the less dangerous method I suggested - Edit/Convert to Profile/ Custom CMYK - you can record this as an Action.
Lets say you have a CMYK file already and you need to change it to a lower ink coverage - the best way is using Chris' suggested method of using a Curve to lower ink density.  its more contollable. Heres how…
• Use a threshold adjustment layer to find out roughly where in your image the maximum ink coverage  is.
• Place eyedroppers at these points.
• Change the readings in info panel to show Total Ink.
• Now use your curves to lower overall density - paying special attention to your Black (k) channel - best practice to lower K channel separate to the rest of the image. This is because K channel holds most of the detail in the image.