The K7 standard

Piezography K7 profiles when used with K7 inks produce 255 separate shades of gray (256 including white). The Piezography profiles are actually curve sets that I make for the QuadTone RIP software. You can think of these gray levels as L (luminosity) values with L value 0 representing black and L value 255 representing paper white. Piezography is the only system which can print such a wide tonal latitude. Other systems can print darker or print whiter, but they can not differentiate detail in the shadows and highlight that Piezography K7 (K6) can. Because darkroom silver paper has less tonal capacity than film, photographers can scan their negatives and produce shadow and highlight detail they have never seen in their own darkrooms.

The Average Display

The problem with average displays such as software calibrated CRTs and LCDs is that they can not display 256 gray levels. So the photographer who can scan 256 gray levels from a negative or capture it with a high quality digital camera, can not actually see the separation in the shadows and highlights on their calibrated monitors.

Calibration systems such as ColorVision and EyeOne use high quality instruments and software to adjust the video board output signals while making measurements of the display. The end result of these calibrations is not only an ICC of the display system, but also a video LUT (lookup table). In order to correct the color temperature, white and black points of the display, the LUT necessarily reduces at least two of the three output channels (red, green, blue).

The end result therefore of a software calibration is a reduced RGB output signal that can no longer reproduce 256 gray levels on the display system. There simply is not enough gray levels to do that. A typical LUT might reduce the 8 bit (256x256x256) output levels significantly so that less than 230 gray levels can be displayed.

What is the first number you can read in the following graphic?

L* values 0 - 23

L* values 0 – 23

You should be able to see all of these numbers if your display is properly calibrated. Piezography K6 and K7 inks and profiles can easily print these separations. You should be able to see them all as the represent the deep part of your image. But this is just the beginning of what Piezography can print. Nearly all printing systems can handle L* (lab) values 0-100. The next test is looking at the RGB values (represented as Luminosity from 0 – 255.

What is the first number you can read in the following graphic?

RBG values 0 - 63

RBG values 0 – 63

On a properly calibrated display you should be able to just make out number 2 or 3. But what if you can not see value 10? or value 15? or worse…  These are very rich dark gray values that Piezography K6 and K7 inks and profiles have no trouble differentiating. Your display is not calibrated for print if you can not make out these dark grays.

Also, it could be your room environment if you are calibrated properly but not imaging in a standardized environment. With all the investment made in printers, cameras, scanners, computers, displays and software & hardware to calibrate everything – you may have overlooked one of the single most important factors: the viewing environment.

The High-Standard Display

Only a few years ago, an imaging professional would not consider anything less than a calibrator-monitor. The core difference between a calibrated monitor and a calibrator-monitor is that the former uses software and an instrument to calibrate the video board, while the latter uses software and an instrument to calibrate the latter.

Thinking of a CRT which has three electron guns (red, green and blue), it is easy to imagine that the USB cable that runs paralell to the video cable on a calibrator-monitor is used to feed real time information back to the computer while the software manipulates the three electron guns in order to obtain a perfect calibrated state. The monitor is capable of displaying billions of colors. The video board can only output 16.7 million. So the calibration modifies the monitor allowing the video board to display 256 gray levels. These monitors carried names like the Sony Artisan Color Reference System; Barco Calibrator; LaCie Blue Hood with Blue Eye. Unfortunately these superior CRT monitors are now discontinued. The market demanded cheaper and lighter. It is a tremendous loss to the imaging professional. But, Artisans can still be found as new close out systems. I believe they are literally worth their weight in gold. Expect to pay $1800 if you can find one.

But, an LCD display has a fixed internal white light source (usually about 6500k) and its not possible to physically alter its color temp, white and black points. Therefore, only software calibration is possible with the exception of the Eizo CG displays and some SpectraView models from NEC. The Eizo is the best known maker now of a calibrator-display. While Eizo sells less expensive Flexscan models, the real deal is the Eizo ColorEdge models. These have a 12 or 14 bit engine attached to the LCD that produces output levels and light sources for each of the pixcells of the display. The bargain as of this writing is the GC222W at only $1,350. You can use your EyeOne or ColorVision instrument with these – but the Eizo software only uses the instrument for measurements sending the results to the LCD rather than the video board. I highly recommend the Eizo ColorEdge LCDs.

An Alternative

There actually is an alternative in purchasing a new CRT which has manual adjustments. When the user calibrates one of these CRTs and uses the advance features of their calibration software, they can manually make adjustments to the CRT rgb guns in order to set the color temperature, white and black points. The result of this will be a significantly increased output video LUT. It is possible to actually create a low-cost high standard calibrated display in this manner. But these CRTs are getting fewer and farther between. Often sold as closeouts, its possible to find the specifications online to determine if the unit as full manual controls. Without them, this alternative will not work.