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Table of Contents

Piezography Manual

By the Numbers

Overview

This is a very old school term that experts were very proud about. They came into Photoshop during the days of CMYK output and were well ahead of the game compared to those who came into printing at the same time they came into Photoshop. What the old schoolers had was experience in using actual CMYK ink values. They new color by its numbers.

They scanned directly to film without any digital image as an in-between. That itself is a difficult concept to imagine. But, it’s true. As the original artwork spun around a gigantic drum scanner the films were being output simultaneously. An array of knobs were turned to alter the output of the film dot being produced with the mandatory requirement that the color (when on press) was correct. That took enormous experience. These old school pre-press people knew what combination of CYMK inks would produce neutral grays and natural flesh tones and bright colors. They were able to isolate any tone and knew its representation in ink values. These ink values were from 0% to 100% in cyan, magenta, yellow and black.

And further, they could convert RGB images into CMYK and devise the type of black plate they required. The expression of black had two forms: under color removal or gray component replacement. The best of the best wrote their own RGB to CMYK conversions. There were not yet Epson inkjet printers that could accept RGB files. Rather, it was all a CMYK world evolving around ink. Printing ink.

So, when we say ‘by the numbers’ - we mean literally by the values of ink. Piezography produces tens of thousands of gray levels of ink. Whether you are imaging in 16 bit grayscale which has 65,536 gray values or 8 bit grayscale which has 256 gray values - you need to only know 256 gray values. You could begin with knowing only 100 values represented by 0% - 100%. That would certainly suit you for working with Epson ABW. But, Piezography is much more sensitive and you really need to familiarize yourself with all 256 gray values. Piezography can actually differentiate between them when used as instructed with a printer/inks both in peak condition.

These 256 values coincide with the RGB values of a grayscale or the Luminosity values of a grayscale where 0 is absolute black (dMax) and 255 is absolute white (dMin). Naturally, 128 would be middle gray.



This Info palette has been setup in Photoshop using the above Info Panel Options. By using the Eyedropper tool or any other tool for that matter, wherever the mouse pointer is placed on an image, the Info Palette RGB and K readouts interactively change to reflect the value of the pixels under the tool pointer.  The tool is reading a sample of the pixels to arrive at these values and you can adjust the size of the sampling by clicking on the Eyedropper Tool and using the Sample Size menu in the Photoshop options for that tool.

I happen to use the 5x5 most often. But, sometimes I need the point sample (1x1) and other times I need a more generalized reading in the 31 x 31 size.

There are some exercises you can do to learn these gray values. You need to come at them slowly and anyone should be able to recognize 21 gray values using the 21 step image files that are so commonly printed these days.

We recommend that you print a 21 step file with the correct Piezography curve and keep this handy. Refer to it while you look at your prints and begin to notice gray values in the prints that you can identify. The 21 step is a gray step wedge in 5% increments. When you installed Quadtone RIP it created a directory: QuadTone RIP / Eye-One / Step-21-gray.tif.  You should not have to guess what a flesh tone’s pixel value is. You should know!


The next step would be to begin to learn the 51 step file which is in 5L increments from 0 to 255 or 2% increments from 0% to 100%. Each column reads top to bottom...


Finally, there is the 256 step wedge from the Piezography Custom Curve package. You can devise your own sets of gray patches for the tone areas that are critical to you.


The whole point of this exercise is to be able to look at a print and know what to change. What value - what exact value do you want a near shadow to be? What is it now? Where do you want to move it to? And this becomes something quite different than staring at an image on a display and trying to make it look “good” or “right”.

Some Gestalt Psychologists have noted that humans are particularly not well suited for staring into light as a manner in which to form their images. The process itself will allow us to organize a reference to what we wish to perceive as opposed to what we actually perceive  - and this happening in real time without our awareness.



There are a number of techniques that can be effective in allowing us to adjust our images on a display. But, these require putting images side by side for before and after, or we are prone to become quickly accustomed to any adjustment we make.

Yet, this effect does not happen when we stare at prints on the wall. We can imagine how we would change them. We can easily mark them up to be lighter or darker. We can write down actual values in terms of L or % that we want to affect. The printed step wedges will guide us.  And then we can rapidly use Photoshop to make these adjustments.

So, the first part of this process is being able to identify what pixel values in the print are. The second part is to express how we want to change them numerically. The third part is changing them in Photoshop. The Eyedropper tool, or rather the Info Window, becomes extremely important.

In the preceding image the mouse pointer is being held over a spot on the wood; expressed as a Sample in the Info Window in Before and After values; as a result of the Curve Point; that is highlighted and expressed as an Input value of L224 that has been made darker to L234.

If one looks at 224 and 234 on the printed example of the 256 step wedge - none of this is guess work. You can literally make strips of gray values to hold up against the Proof when you are looking at it and studying it - to get an idea of what the values are. You can then write notes in the margins of the Proof - or mark up the Proof directly. And always it is not a matter of what you are supposed to do, but rather what it is that you want to do. None of that will ever be evident by staring at the image on a display. It all comes down to making a Proof - pinning it up on a wall - and staring at it. What does it need?

The same Gestalt Psychologists who reckon we are ill equipped to stare into light also insist that it takes at least three minutes of looking at an artwork before we can objectively make decisions. And so therefore, most of our time should be spent in looking at prints rather than displays. And you may ask then, why buy a fancy display? It’s a Catch-22.

Favorite Numbers

Photographers begin to develop them when they become Printmakers. They tune into certain gray values that they describe as “creamy”, “delicious”, “buttery”, “steely”, “dark as twilight”, “dusky”, “dusty”, “whisper-like”, “pale”, “quiet”...   What are your favorites? What do you like? Can you equate them with specific L values? Is there a style of printing you wish to emulate? Can you identify it numerically?

Certainly, printing should be felt. It should be a felt sense - rather than a mathematically derived result. But, in learning anything we need first to be able to develop a vocabulary - a way of expressing it (if even only to ourselves), discussing it, designing it, executing it, perfecting it.

When we look at images on the internet that we think are unusual - we can sometimes copy and paste them into Photoshop to examine the numbers. By doing so - we are able to see how the photographer expressed it (executed it).