The standard is based on films available in the 1930s and 1940s, and many of today’s films are substantially different.
The implication is the fractional gradient method may not be applicable to film emulsions designed after the standard was developed. This is possible, but not probable. The statement suggests no one was aware of how the characteristics of new emulsions worked in relation to the fractional gradient method. For this to be true, no subsequent film testing could have occurred over the last 80 years since the original First Excellent Print Test was performed or if there was testing, the standard was never updated when testing indicated a necessity. Both strain credulity.
Clearly, new emulsions are extensively tested during the creation process and prior to marketing. Standards are reviewed every 5 years. Any problems or advancements that crop up in the interim would be considered and reflected in a revision of the standard, as with the 1960 and 1993 film speed standards for black and white negative films.
My understanding is the 1993 revision came about because films with T-grain technology, using the developer stated in the standard, didn’t produce speeds equivalent to commercially available developers such as the ones utilized when creating the new emulsions. The standard didn’t accurately reflect real world use with T-grain films, so the standard was adjusted. Other updates were also made to better reflect real world use. The value for ΔD may have been refined from 0.80 +/- 0.05 to 0.80 in for the 1993 standard or maybe for a previous one. I’m not sure.
One of the reasons for the 1960 revision was to reduce a safety factor that was no longer necessary as technology allowed for tighter controls. The statement about the standard being based on films available in the 1930s and 40s is similar to one made by Lloyd Varden in
ASA Exposure Index: Dangerously Safe. Varden argued the safety factor described in the standard pushed the exposure proportionally higher on the curves of short-toe films than medium and long toe films. An important distinction is the safety factor actually is part of the ASA EI rating and not the fractional gradient film speed. Varden proposed reduction of the safety factor. The 1960 standard did reduce the safety factor. Your proposal appears to effectively reinstate it to some degree.
Another reason for the revision was to simplify the method of determining the fractional gradient speed as the current method was laborious and tended to introduce experimental errors. C.N. Nelson and J.L Simonds devised two methods as described in their 1956 paper for the Journal of the Optical Society of America,
Simple Methods for Approximating the Fractional Gradient Speeds of Photographic Materials. One of which, the Delta-X Criterion, became the method for the new standard. Concerning the films used in the analysis of Delta-X, Nelson and Simonds write, “The relation between ΔD and ΔX was, therefore, measured for the forty D-log E curves of the negative materials used in the original derivation of the 0.3G fractional gradient speed criterion. The results are shown in Fig. 10(a). Similar measurements were carried out for a number of current films in several different developers. The values are given in Fig. 10(b).”
Research into the photographic process has continued to progress past the early 1940s. The tone reproduction curve in the tone reproduction diagram compares the original subject to the finished print which can also include the viewing conditions. The objectively produced curve can be interpreted to determine print quality from tone reproduction characteristics. In fact, the degree in which extensive studies have been done make it possible to predict the level of perceived quality simply by evaluating certain curve attributes effectively eliminating the need for judges and allowing for a multitude of hypothetical situations of film / paper combinations.
The following is an excerpt from the paper, Simonds, J.L.,
Factors Affecting the Quality of Black-and-White Reflection Prints, The Journal of Photographic Science, Vol. 11, 1963. p. 27-30, which represent some of the results from testing 18,000 variations.
“Consider two negative films with D-log E curves as shown in Fig 3. Film A has a curve with a short toe; Film B has a curve with a long toe. The density ranges of properly exposed negatives on both films however, would be similar, permitting printing both negatives on the same contrast grade of paper."
"Fig 4 is a plot of print quality as a function of log-camera exposure for the two films. In plotting the curves, it is assumed that, for every negative exposure given, the optimum choice of paper-contrast grade and printing exposure has been made. The abscissa represents the log exposure of the darkest significant element in the scene.
Both curves reach the maximum quality level of 100 per cent. It can be seen, however, that the long-toe Film B is capable of producing prints of highest quality over a greater range of camera exposures than the short-toe Film A. To achieve optimum quality with the short-toe film requires a critical choice of slight under-exposure and subsequent printing on a high-contrast grade of print material. With extreme over-exposure, however, the long-toe film results in negatives with an excessively high density range which available print materials cannot accommodate; hence, a loss in print quality results. The short-toe film shows a superiority in this over-exposure region.
The curves of Fig 4 assume studio photography in which the flare light in the camera image is at a minimum. In outdoor photographs, flare light degrades the camera image of scenes containing large, bright areas of sky, sand, or water. Fig 5 shows the effect of adding a normal amount of flare light in the photography of an outdoor scene with Film A, the short-toe film. The dashed curve is the effective characteristic curve in the presence of the flare light. The effect has been to convert the short-toe film into a long-toe film. In that case, the curve of quality versus log-camera exposure for Film A would be more nearly like that given for the long-toe Film B. The effect of camera flare on Film B would be to give it an even longer toe, creating an excessively flat negative which a normal amount of camera flare is present. It must be pointed out, however, that the differences in print quality obtainable from the dissimilar films are slight. Only when other factors in the reproduction system are optimized will the inherent quality differences became apparent to the experienced observer.”
From the same paper. Something to consider.
“The results obtained from the digital studies are in excellent agreement with accumulated experimental evidence. The new data are unique in that they provide quantitative relationships in place of the qualitative relationships that have been deduced from past studied. The use of high-speed computers makes feasible the investigation of the quality attributes of a great number and variety of photographic systems. A recent evaluation of the photographic quality represented by 18,000 variations in reproduction involved approximately three hour of computing time on an IBM-705 computer; a similar investigation by direct psychophysical methods in the laboratory would be prohibitively expensive and laborious.
The data from many such computations strikingly point out an important consideration when direct visual comparisons are being made of the quality of prints obtained from different negative materials; small, but subjectively significant, quality differences can be realized by changing the D-log E characteristics of the negative material; but these small quality difference can only be appreciated when the levels of all the other variables of the reproduction system are carefully controlled. The importance of optimizing the printing conditions cannot be emphasized too strongly when comparisons are being made of prints made from different negative materials. Even a slight error in print exposure can obscure a potential quality improvement offered by a negative material with an improved D-log E curve shape. Examination of the data of these studies has emphasized the fact that a valid comparison of the relative merits of two films requires extreme care and accuracy on the part of the technician preparing the demonstration prints.”
Makes me wonder about the conclusions and general observations photographers make concerning the qualities of a given film in a given developer or about one emulsion vs another.
