The Matcher accepts film and paper data from the Plotter
and combines them graphically to demonstrate how the subject tones are converted
to negative densities and how those negative densities are translated into print
image values. Image tonality is affected by each of these steps so the gradation
characteristic of the final print image is really a sort of average of the
characteristics of the film, the film developer, and the printing paper.
The print "look" may also be influenced significantly by process variables such as camera and lens flare, over- or underexposure of the film, over- or underdevelopment of the negative, paper grade or filter changes, and by relatively slight variations in print exposure. By displaying this whole image-forming sequence in simple graphic form, the Matcher makes it easy to review, adjust, compare, and predict the image "look" that can be produced by various films and papers under any simulated condition of use.
The "look" of a print image is largely due to gradation, that is, the distribution and relationship of the various gray tones. Of course the tonal extremes of black and white are fixed, but the grays between them can be shifted toward lighter or darker values, and local contrast can be changed significantly by changing materials and process variables. Technically, at least, a "good" print is one that retains the desired detail in both ends of the scale; but "good" prints are not necessarily attractive prints. Unless the internal grays are related for best visual effect the print will not "sing."
This is a highly subjective matter, of course, but when you've identified a set of materials that produce what you consider to be beautiful print quality, the Matcher will help you define that quality in graphic terms. Then, using that "ideal" gradation characteristic as a standard, you'll find it easy to try various combinations of film, film developer, and paper to see which sets are most likely to produce the gradation you prefer. Of course it's equally easy to identify materials' sets that can be used for creative or expressive distortions of reality. In other words, the Matcher is a remarkably useful tool for "what if?" experimentation.
Gradation is directly affected by the contours of the film and paper characteristic curves, and the critical regions of both curve types are the toe and shoulder. The toe begins at the base+fog density level (Dmin) and extends through the lower section of the curve where local contrast (curve gradient or slope) is increasing at an accelerated pace as exposure increases. In the central, "straight-line" portion of the curve, gradient is constant as exposure increases. The curve shoulder begins above the straight-line region at the point where gradient is beginning to decrease, and extends to Dmax (the point where there is no further increase in density as exposure is increased).
Practically speaking, we never reach the Dmax of ordinary film materials, but the film toe contour just above Dmin is almost always a significant influence. We don't often use much of the paper curve's shoulder, either, but it's sometimes a factor; the paper curve toe, on the other hand, is always important.
Each of these curve regions has a predictable affect on print image gradation. In general a film toe with a long, sweeping contour will tend to compress the dark tones in the print, reducing shadow separation and contrast, and darkening the middle tones. The same "long-toe" characteristic on the paper curve tends to reduce highlight contrast and lighten the print's middle tones. A "short-toe" film curve (that is one that displays an abrupt increase in gradient) tends to increase tonal separation and contrast in the shadows and lighten the middle tones; a short-toe paper curve increases highlight contrast in the print image and renders the middle tones darker than normal.
Few film curves have shoulder contours that are obvious enough to have a pronounced affect on image gradation, but any departure from a straight line will have some effect. A gradually rounded (decreasing gradient) film curve shoulder tends to compress highlight contrast in the print image and lighten middle values, just as a long-toe paper does. In the few instances where the film shoulder gradient increases progressively (an "upswept" shoulder), the tendency is to increase print highlight contrast and darken middle tones. Most paper curves don't display much shoulder rounding within the usable image range so their influence is not great; but when a shoulder tendency is evident it tends to reduce deep shadow contrast with some darkening of middle values.
From this description you can see that the film toe and the paper shoulder both affect the print shadows, while the film shoulder and paper toe both influence image highlight tonality. When these characteristics work together they can produce fairly extreme tonal effects but when they're in opposition they can neutralize each other. When you understand how these curve contours relate to print image gradation you'll find it easy to identify the materials' combinations that are most likely to produce the "look" you prefer. The Matcher is designed to help you do that. It allows you to compare the gradation characteristics of any combination of film, film developer, and paper, for which you have existing Plotter data files.
Of course, there is some danger in taking this information too literally. The various materials' curves represent characteristics that apply specifically only to their individual test conditions; your use of these same materials may produce somewhat different characteristics. Also, the gradation shifts that are so obvious on the computer screen may not be as obvious in the print, especially in the darker print zones where tone differences are difficult to distinguish, visually.
In fact the main virtue of the Matcher may not be the technical or factual data that it produces. By suggesting the existence of gradation subtleties that you may have been overlooking, and by dramatizing the gradation differences that can be produced by different combinations of materials, it may simply inspire you to examine your prints more critically and help you appraise their quality more effectively, thereby ultimately enhancing your appreciation of the tonal elegance of the fine print image.