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Piezography Linear or Match to Screen or Hardware Calibrate?

Jon Cone
published on 03/27/2019 14:50:43

We introduced an optional method for printing Piezography prints a few years ago for users with OS X operating systems. It is not necessarily the preferred method of printing for OS X users, but more so a byproduct of being able to perform this method in OS X. Many of these users were asking for technical support because they thought that their prints looked too "flat" in comparison to their displays.

We call this option Match to Screen and its real purpose is to make Piezography prints that have darker shadows than they should. Not blacker shadows! Rather, this option makes the shadow detail darker in order to benefit those who do not have displays that can be properly calibrated. Therefore this option may more closely match the images on uncalibrated or (under)calibrated displays which can not display the amount of shadow detail that can be printed with Piezography.

Apple LogoThis method was the accidental byproduct of an OS X issue that surfaced way back in the day when OS X suddenly began "silently" converting images that did not have embedded color profiles. Apple had made the decision that if an image didn't have a color profile attached to it, ColorSync should convert it to sRGB. They had not considered that the image might actually be a grayscale image and had a grayscale embedded profile. We have always instructed that grayscale images must be embedded with Gray Gamma 2.20 profile. We issued work arounds for several OS X upgrades until Roy Harrington released his QuadTone RIP Print-Tool for OS X users. Print-Tool allows the user to turn off the OS X color management. Windows users never had this problem and QTR did not make Print-Tool available for Windows users. And this is why Print-Tool is now a requirement for the use of Piezography on OS X.

What we took advantage of with Print-Tool is that if we selected the Print-Tool Managed option we could have the image converted to an ICC profile (of our choice) prior to its being printed with QTR. Conventional non-Piezography QuadTone RIP workflow uses QTR derived ICC profiles as part of its calibration process. But, we found that making a QTR ICC prints much too dark overall. So, we wrote an application we use in-house to produce an ICC Output profile that closely matches what conventional displays produce when grayscale images are viewed. We thought that this would be of enormous benefit to users that imaged on iPhones, MacBooks, iMacs and other displays which were not designed for printing. We teach this during our workshops as an alternative and we offer this option as part of the online printing services at Cone Editions Press.

This option, as well as the "normal" way of printing, are both mentioned in the Piezography manual that is kept up to date on our community website. If you haven't downloaded the Piezography installer recently, please do! It will install two special output ICCs that are used with the Match to Screen option. 

Two methods:

  • Piezography Linear is when a Piezography media profile (QTR curve) prints with 256 distinct separations from dMin to dMax. The 256 gray steps transition from one to the next along a straight or nearly straight line. The resultant printed image is smooth and predictable and will match Gamma 2.20 hardware calibrated displays (Eizo CG, BenQ Palette Master, NEC SpectraView) that are calibrated to print. This has been the standardized way to print Piezography for many years.

  • Piezography Match to Screen is when an image is first converted to the tonal curve characteristics of a special Piezography Output ICC profile just prior to printing. The proprietary ICCs we provide convert the image to more closely match displays that are not properly calibrated to print. The two special Piezography Output ICCs we supply for this purpose are Piezography-Matte.icc and Piezography-Gloss.icc. They are installed during installation of the Community or Professional Editions of Piezography for OS X users.

I will explain what is going on with the two methods...

Firstly, I want to credit Keith Schreiber for the basis of the work for plotting how Piezography prints when using No Color Management, and PrintTool Managed with a Piezography ICC profile and with a QTR ICC profile. Keith is one of the premier platinum/palladium printers in the world and is one of the best beta testers that anyone could ever hope to collaborate with. He was instrumental in our development of PiezoDN software for making digital negatives. If you're into PiezoDN digital negative making you will probably have benefited by his knowledge already on our PiezoDN Community forum. I've heard from a few people lucky enough to take a private Pt/Pd workshop with Keith in Taos, NM. I took the graphic Keith created for the InkjetMall community forum and altered it to suit my purposes.

What Keith plotted was the differences between printing linear (no color management), an ICC that we created for outputting, and using an ICC profile produced by QTR. The chart measures dMax from the bottom left corner to dMin at the upper right corner. If the plot dips down it indicates the output value is darker than linear.

The Piezography ICC when selected in Print-Tool will produce a print that has shadows that imitate a display that is too bright (too dark), rather than just making the print overall darker. This has proven effective for our users that do not have access to displays that reveal all the shadow detail that Piezography can print. Having said that, I believe that they are missing much! The investment of an appropriate display should be on their must-have list!

The QTR ICC profile (green line) made the entire tonal range darker - producing an overall too dark print. The Piezography ICC profile (blue line) darkened the shadows and then eases up at the mid-tones and leaves the highlights as they were.

Of course the red line in the chart indicates linear which is the ideal print. An image when printed linear needs only to be edited on the display to suit the intents of the imager. But, that requires a display that can accurately render shadow detail. The Catch-22 is that most modern displays did not anticipate having to display what Piezography can print. After all, Epson, Canon and HP ink sets can't print the same shadow detail that can Piezography. But, as luck would have it, hardware calibrator displays are relatively inexpensive today:  (Eizo CG, BenQ Palette Master, NEC SpectraView).

So, let's make sure that if you intend to print Linear that you understand how to set these options in the QTR Print Tool:

Above is the conventional way to print a Piezography print. No Color Management is selected. And to remind you that an embedded profile is required! In this case, the image is an RGB grayscale and Adobe RGB is embedded when the image is saved from Photoshop or Lightroom. It is the only profile you can embed for color images. Other profiles will cause the image to be converted prior to printing (which is bad.) If the image is a single channel grayscale, then only Gray Gamma 2.20 can be used. Any other Gamma or Dot will cause the image to be converted prior to printing (which is bad). When you run print, you must choose the Piezography media QTR curve for the media you are printing.

And, let's make sure that if you intend to print Match to Screen that you understand how to set these options in the QTR Print Tool:

Above is the optional way to print when you use a Piezography supplied ICC profile (Piezography-Matte.icc or Piezography-Gloss.icc). Print Tool Managed will convert the image(s) to the contrast adjustment of the ICC prior to printing with the correctly selected Piezography media QTR curve for the media you are printing. You should select Relative Intent w/BPC. Again pay attention that you have an embedded profile. Not having one is bad, as is having one other than Gray Gamma 2.20 or Adobe RGB.

By example, Cone Editions Press online Piezography printing offers both print options  

When we set up the online printing services at Cone Editions Press, we anticipated that many of our customers would not have displays designed for printing. We anticipated that they would not have seen the shadow detail in their images and therefore our printing these images with shadow detail would appear "flat" to them. On the other hand, we did not want them to miss out on what is arguably one of the best features of Piezography which is to be able to discern between absolute black and just nearly black. Piezography can separate shadow tones unlike any other system in the world.

So, we offer two methods and try to explain them like this: By default our prints will match your monitor. If you want to get the "piezography look" and create endless shadow detail, you can select "Piezography Linear." It requires more work! If you select Piezography Linear please Download Linear Instructions and ICCs.  If you're curious here is the link to the Soft Proof ICCs we provide and instructions for linear printing. What we have found is that most of our customers order a Match to Screen and a Linear version of the same image for comparison. Most end up editing their images for linear printing because Piezography shadow detail is so satisfying! 

Software versus Hardware Calibrated Displays

Displays have become brighter and brighter in the last few years. And they're expensive!  And the truth of the matter is that fewer and fewer people are printing. Rather they prefer to share images and look at images on displays. They are gaming and streaming movies on their displays. They are editing videos. They are doing all kinds of things that are better benefitted by brighter displays with enormous contrast ranges of 1000:1 and higher. Unfortunately, the brighter a displays is the darker it is. The majority of these displays are adequately served by having 8-bit internal video engines that produce 16.7 million colors and are matched to the 8-bit video boards of the computers that are attached to them. These displays rely on calibration processes that are stored on the users computer and load as a video board LUT when the computer starts up. This is what we refer to as software calibrated.

Software calibration packages from xRite and DataColor improve color accuracy for general work and color printing. But, modifying the video board in order to change the appearance of the display is done at the expense of fidelity. 8 bits equals 16.7 million colors and that seems like a lot, but it is only 256 levels or red x 256 levels of green x 256 levels of blue. Software calibration can cut down the output of one or more of these 3 channels from 256 to as low as 180 levels. This lack of fidelity can make Soft Proofing much less reliable and there are seldom enough output values to display 256 gray levels for a monochromatic image.

Several years ago, a hardware calibrator display (designed for printing) was very expensive. Some still are!  But, in the last 1-2 years the prices have been plummeting. There are now outstanding displays in the sub $400 region which are designed to be calibrated for print and are at their peak with contrast ratios as low as 200:1. These displays will have at minimum a 10-bit internal video engine that produces more than one billion colors. The calibration packages designed for these displays ensure accuracy by physically tuning the actual display and storing the results as built-in look up tables (LUT) in the display. Because it is all done in hardware, we call this hardware calibration.

BenQ, Eizo ColorEdge and NEC Spectraview sell software and hardware calibration displays. The links I just provided point to their hardware calibration displays. 

If you invested already in a software calibration kit, the good news is that most of the hardware calibrator displays support the use of instruments from xRite and DataColor and others. You can most likely use the instrument for the hardware calibrator display if it requires the purchase of a measuring instrument. Some come with the instrument. But, you will need to disable the software that ships with these instruments that you have been using as it creates a video LUT when your computer starts up. That LUT necessarily impacts your video output producing less colors than your computer is capable of. Once you switch to a true calibrator display, you must disable the software calibration you were previously using.

We believe that if you are going to print with a system that can render far more gray separations than you can see on an ordinary display - that you should get a display that is designed for printing and it should be one of the ones I linked to. And you should not be tempted to calibrate it with the software package you purchased for your conventional display. Doing so makes the whole operation moot!  You can use the instrument you've already invested in - but you must use the ColorNavigator software for Eizo, the SpectraView II for NEC, and the Palette Master for BenQ. 

If you've been to Cone Editions Press and plugged your laptop into our displays during a workshop, they were either Eizo CG or NEC Spectraview. When we unplug them, the calibration remains with the display. That's hardware calibration! 

Now how do we really feel about it?

There are those times when printing with the second option (Match to Screen) can produce an effect that is pleasing in ways. So, experiment on your end...  the output is always linear... it is only the image that is converted to a different contrast with Match to Screen. You may find that using it with PiezoDN lets you produce Platinum / Palladium prints (normally very flat and long in tone) that are more contrasty like your display.  Yet, using a properly calibrated display and a Platinum / Palladium print Soft Proofing ICC you would see the long tone of the Platinum / Palladium print and be able to adjust the image to your liking. You could increase the contrast for example, but not at the expense of shadow detail. You can not make the Platinum / Palladium print have a darker dMax but you can be fully responsible for making the shadows darker while carefully preserving details. With a software calibrated display this detail is just combined with darker values as an overall dark mass.

Finally, for those considering that they only have space for one display...  A hardware calibrator display stores the calibration in hardware and most of these systems can switch from Print Calibration to Video Calibration to any custom Calibration on the fly in just a few seconds. One of these displays can be bright enough to watch Netflix and yet dim enough to compare to prints. Some of these displays are now available in 4K and a few in 5K (may break the bank.) 

What's the next step?

Years ago (1990s and 2000s) anyone doing serious calibrate to print imaging worked in a D50 environment with expensive gear. More than likely they were imaging in CMYK and perhaps using Barco or Sony Artisan displays. Some of these were so heavy it took at least two people to move one. I started with Barco Calibrator CRT displays on SGI computers. But, I was stronger in those days!  I certainly do not miss the short life and weight of a CRT. But, I do miss the color accuracy of the Barco and the Sony Artisan.

But, I do miss the emphasis on imaging in a D50 environment. The specs of such an imaging room included very dim ambient lighting of about 50LUX which could only be 5000k in temperature. The display was calibrated to print at 5000K. A 5000k dimming viewing booth was placed adjacent to the display and illuminated to the same level as the display. Whatever argument you might make about 5000k vs 6500k, humans are better adapted to making color matching decisions at 5000k. Eventually, the ICC was invented and Soft Proofing with ICCs closed the loop between what you see and what you print. During these years, ConeTech supplied IRIS 3047 printers and drum scanners to fine art Giclée studios who were all taught to image in a D50 environment. It was just what one did in those days. 

Imaging environments are still really important. You should be imaging in a dimly lit room. And your display should be able to be calibrated to a brightness setting of about 80-85. If you work in a brightly lit office with windows, that's not going to be possible. Dimming Viewing Booths are still a good idea. We like the GTI units. Today they can be set to 5000K (D50) or 6500K (D65). Having only one color temperature present is also important as humans can not adapt to more than one color temperature of white light. We tend to see different color temps as warmer or cooler. 5000k is still the color temperature in which humans can not detect any more red than green than blue. It is neutral to the average human observer and the preferred temperature under which to make color comparisons. This temperature works better with a hardware calibrated display.

Obviously, galleries and museums do not display under 5000k. We using an imaging and proofing environment only to produce a match between the proof and the display and to make corrections that when soft proofed correlate to what we see in the proof. If the term Soft Proof is new to you - it is when an ICC profile is produced for a specific printer, printer driver settings, ink and media. It is then loaded into the imaging software as a "Soft Proof" ICC profile which changes the display to match that output process. With a software calibrated display, a soft proof ICC profile is hit and miss but mostly miss. With a hardware calibrated display it can produce a match to output that is the very high 90s% of accuracy. They can even be used to show the color of the paper and how dark the black ink is by reducing he screen display dMax to imitate the light the black ink reflects back to the eye.

Screen Capture of image on the left taken from Photoshop without Soft Proof selected. Image on the right is a Screen Capture of the same image in Photoshop with Soft Proof selected using an ICC profile made from a Palladium print.

Screen Capture of image on the left taken from Photoshop without Soft Proof selected. Image on the right is a Screen Capture of the same image in Photoshop with Soft Proof selected using an ICC profile made from a Palladium print.

This type of imaging takes some getting used to. Unless you have the whole set up (dimming viewing booth adjacent to the display in a dim room), suddenly turning on a soft proof can make the image on the display appear pale and thin. It is in the D50 environment that you realize the display really matches the print. Prints do not reflect much light. They're low contrast. A properly calibrated display is supposed to look like a print. Hence, lower contrast ratios. In the case of the Palladium print above, soft proofing it allows adjusting it to realistic expectations. dMax of a Palladium print rarely rises above 1.45 (with Malde-Ware) but is more typically in the 1.31 range with potassium based process. The soft proof will not permit the screen to get darker than the measured dMax from the print nor brighter than the measured dMin. The color of the image shifted to the actual color of the Palladium print as measured.

How the Soft Proof ICC profile was made is by printing a target as a negative and contact printing it to the Palladium print, exposing, developing, clearing and drying it. The printed target was then measured with the QTR ICC profiling software. A 21 step strip can be added to negatives or to Piezography prints for this purpose. But, the accuracy is dependent upon the quality of calibration of the display. Matching the print to the display requires a viewing booth to really make the match apparent to the human eye. Running from the viewing wall in one room and trying to remember what it looks like as you run back to see the image on Photoshop is definitely not a best practice!

So, I've gone from showing you a method to match prints to uncalibrated displays to a method to match a print to a hardware calibrated display (best practice).