I spent 9 months with MegaVision teaching digital photography in 255-0 and 0-100 scales before it dawned on me that I could use the T2’s 0-100 Show Info report scale to infer Zone System values of 0-10; a one’s place is the difference between the two number progressions. MegaVision has since added to their software, a 0-10 Show Info that reads direct zone values. This has greatly improved my ability to communicate photographic concepts to new users. Although most shooters haven’t thought about the Zone System since their photo school days, they find the approach vastly superior to the 256 scale.
One inherent advantange the Zone System has when considering the evaluation of reflectances, is relative placement on multiple targets. Consider that Zone II is the same distance from maximum black and minimum white on all targets, regardless of media or density range (neg, chrome, color, b&w, injet, dye sub, monitor, or printing press). The other Zone System values are no different, they have the same relationship to absolute black and absolute white on all targets. It’s traditional to use terminology relating to the target when discussing value. Printers use ink densities, scanners use gray levels, photographers use f-stops or Zones. The Zone System allows the use of a terminology photographers can use for all of these targets because Zones relate easily to other targets, unlike ink densities on monitors or gray levels on press.
Photoshop will allow the use of the Zone System to verify the quality of a digital file. By choosing grayscale for one of the two Show Info options, Photoshop will display a 0-100% (dot percentages) scale from which you can infer 0-10. Be aware that 0 (threshold) in the zone system is black and differs from 0 in grayscale, which is white (printer’s inks start their threshold at white paper which has no ink). You will need to invert the numbers. To arrive at the zonal value from the grayscale report, subtract the dot percentage from 100 and move the the decimal one place to the left. 35% from 100 is 65. The zonal value is 6.5 (VI 1/2). The following relationships apply. 256 level values follow for applications that do not report ink densities.
If, for instance, you place Caucasian skin tone on Zone VI, it will read 40%. That is a reasonable placement for skin tone; verifying the reflectance in the software will guarantee your wishes for that density (and every other important value you place and verify) on your intended target; if it isn't modified by someone else. That modification is where the process of placing images on a printing press can become obscure. Actually, any output (Iris for example) generated by an outside imaging service can become difficult. Separators for example will often “adjust” your files for proper output to a given target.
Consider sending a color neg to a custom lab. If you don’t like the print, the lab will remake the print to your liking. They will often do it for no charge. Service bureaus and color separators traditionally do not extend the same service to photographers. You pay for any misunderstanding in the translation of your image onto the imaging service’s media. Inclusion of the highest quality output you can generate (a print for example), along with your file will go a long ways toward generating success on your first try when using the outside service. It’s like sending a transparency along with the color neg: it’s something to match. The advent of cheap, high resolution inkjet printers (720-1440 dpi) can help the photographer communicate his intentions to the outside service.
The use of a system to predict and verify any value in the transition of tone from highlight to shadow is perhaps the most important tool for the generation of high quality content in the imaging process. Knowing the final result breeds confidence. It also allows creative departure from reality (abstractions for instance) and makes the problem solving of difficult situations more easily accomplished.
Using the Zone System to aid the manipulation of digital images should start and end with curves. If you are scanning film based images you will begin with a file and you will choose the final transition of tone with a curve. If you are capturing with a digital camera you will start with a file. If the camera is tethered to a computer, you’ll use a curve to choose custom transition of tone in the displayed image. If you are shooting a non-tethered camera you’ll open the image in an image editing software package and you’ll want to adjust its transition of tone with a curve. Key to the digital process, just as in film, is applying the proper number of tones to the intended target. Just as you can’t effectively print a neg scaled for grade 2 paper on grade 5 paper, you cannot easily print a file scaled for a high quality sheetfed stock on newsprint. Curves can change the number of tones and their transitions. Refer to any number of good texts available on the application of curves.