Our bad! We did not verify.
From time to time, we have received tech enquiries from Mac users that have tried to reproduce a Piezography print from the same file printed with an earlier version of Photoshop. They tell us that the image is printing darker than their display. We then usually set about trying to determine if there is a problem in the users system.
You would think that with so many thousands of Macintosh users of Piezography that this issue would surface more often. But, most users do not reprint libraries of images as often as one thinks. And fewer still match the latest print to a bon a tirer image or proof. Piezography K7 curves are so forgiving that K7 output quality always remains amazing. It takes quite the out of whack printer or a contaminated or old ink supply to reveal a reason for the need of a custom curve or corrective linearization. The reason by the way, is that our curves use multiple overlaps with a lot of back slope. This is proprietary to the Piezography profiler.
As a result, it often takes a very clearly documented case to bring an issue to light. We received that yesterday.
Today we did a very simple experiment that I am embarrassed to say that I could have done years ago. Although we are Macintosh concentric in our imaging we print using Windows servers and the stand-alone QuadTone RIP. In R&D, we use Windows. The Piezography profiler and the Piezography Linearizer are both Windows applications. This escaped our notice as a result.
When we released PiezographyBW ICC, we printed with a Gamma of 1.8 by creating profiles with a Gamma of 1.8. Because color management was used via an ICC profile, we controlled the process. When we released Piezography K7 we switched our profile Gamma to 2.2 because the CRT display was going extinct and most users would soon calibrate their LCDs to the native 2.2 Gamma rather than the proofing industry’s 1.8 Gamma. We instructed our users to assign a Gamma of 2.2 to their images, if they wanted to preview the correct contrast of how their images printed with K7, and turn off Color Management in Photoshop.
When we had the user in Photoshop select “No Color Management”, the Gamma was passed through intact to the QTR driver, because the K7 curve produces a Gamma of 2.2. The Mac OS and Photoshop remain hands off to the process.
But, since the release of Photoshop CS4, “No Color Management” is not an option. What we find is happening is that by selecting “Printer Manages Color”, the Gamma being sent to the QTR driver by either Photoshop itself or the Mac OS interfering is actually being driven as if it’s Gamma 1.8 (the internal Mac OS printing Gamma). The image is not even being converted from 2.2 to 1.8. The result is that the image is darkening quite a bit from that what the user is seeing on their screen.
The fix is easy, I am even more embarrassed to say…
Instead of selecting “Printer Manages Color”, select “Photoshop Manages Color” and select Gray Gamma 2.2. By doing so, the image data going to QTR will be unaffected by either Photoshop or MacOS. Please note that this will only work if your grayscale image is already assigned Gamma 2.2 as we instruct.
Now, we understand that this does not work for regular QTR workflow and is not recommended by QuadTone RIP. But, Piezography is not regular QTR workflow. We produce the K7 curves for the author of QTR and he includes these in the QTR download. But, QTR has not included our own manual for download because our methods differ from their instruction. Obviously this might cause confusion.
You can actually select Gray Gamma 2.2, or Generic Gray Gamma 2.2 (both of which will not correct this for regular QTR users of non-K7 ink sets.
Now, if you have not been following our guide to using K7 correctly from the beginning. Remember, you must assign Gamma 2.2 to your Grayscale mode image. Photoshop will then display the image to you in its correct printing contrast. Then on <=CS3 – select “No Color Management” – or in >=CS4 select “Photoshop Manages Color”. When you print, select the correct K7-2880(dpi)-xxx-xxx curve that matches the media you are printing. Select the highest quality print option and 2880 dpi. DO NOT ADJUST GAMMA OR LIMIT. Print! Easy and perfect. (and now corrected for greater than or equal to version CS4.