"fixing" PDFs with excessive TAC?

[lfelton]

We currently receive "problem PDFs" where either the CMYK ink levels are too high or, most commonly, the PDF is RGB and when we convert to CMYK, the TAC is too high. This is not really an issue where files are going to a digital machine, but is for litho, especially uncoated stocks.

I know that Gray Component Replacement (GCR) and Under Color Removal (UCR) are techniques that can reduce TAC, but I can only find tools costing tens of thousands of dollars (i.e. Alwan) to achieve this.

Am I missing a trick here? I'd like to "fix" customer's PDFs, not just reject (for example) MS Publisher created files. Can anyone point me in the right direction for researching a solution?

[meddington]

or, most commonly, the PDF is RGB and when we convert to CMYK, the TAC is too high.

By what means and what profile are you currently converting to CMYK? Choice of profile will make a difference whether or not your TAC is too high.

[Lukas Engqvist]

The TAC is in the profie. We tell our customers to use the ISO Coated v2 300% profile from ECI if they don't want to use our house profiles. There is no good generic standard profile for uncoated IMO.

[lfelton]

Gentlemen, thank you for your responses and I was certainly missing a trick.

Having looked into this a bit further, it turns out to simply be a misunderstanding over TAC with my pre-press guys. They were using FOGRA39 as the output profile and had somehow misunderstood that the maximum TAC was greater than our standard pre-flight fail setting of 310%. They interpreted the higher TAC (and subsequent pre-flight fails) as being caused by the RGB->CMYK conversion not setting the maximum TAC correctly, when in fact they simply had a mismatch between the profile and the preflight limits.

Lukas - I gave them the 300% ECI coated profile as you suggested, this is plugged in and working fine. Given your comment about generic uncoated profiles, would you not recommend using the generic ECI ISO uncoated profile, or is that the "best of a bad bunch"? I think you are suggesting that uncoated papers vary significantly enough that specific profiles should be written for each one to achieve good accuracy. Do I understand you correctly?

[Lukas Engqvist]

There are two issues with the uncoated for us in Sweden. Firstly customers aren't interested in paper stock wich confrms to ISO, it is much bluer/greyer. Secondly the total amount of ink. We are working on getting an uncoated that will work for several graphics firms. But have our own measure data and separatuion where we use 240% Ink limit.

[Louis Dery]

There are two issues with the uncoated for us in Sweden. Firstly customers aren't interested in paper stock wich confrms to ISO, it is much bluer/greyer. Secondly the total amount of ink. We are working on getting an uncoated that will work for several graphics firms. But have our own measure data and separatuion where we use 240% Ink limit.

Hi Lukas,
FYI, we just did the same for a paper manufacturer in Canada called Cascades.
Profiles are made with 240% ink limit like you are using in your separation.

More info at
TGLC - Rolland Enviro100 Print - Profils ICC

Louis Dery
TGLC inc.