Spur Nano Edge and Orthopan UR (January 14, 2010)


Introduction


Hardly a day passes without the announcement of another “thundering herd” of new digital cameras just over the horizon as one esteemed commentator of the photographic world describes the assumed arrival of new Nikons (but the same is true for Canon and all the others in the lemming race over the cliff). Being an avid admirer of classical Westerns, I can imagine the Rawhide camera herds roaming over the prairie with the real men (the camera reviewers) coaching them to the slaughterhouses in the civilized world.
Silver halide technology, as a contrast, but staying in this metaphor, seems to be located in the quiet drugstore in the small town where a stern but righteous sheriff is occupied with saving damsels in distress.
I have reviewed modern microfilms (Orthopan, Adox CMS20) in a range of developers and noted that these emulsions have a number of characteristics that make them a viable and interesting alternative or complement to the digital capture techniques. Any one who still uses high precision miniature cameras (Leica M series, Canon F series and Nikon F series as examples) and is prepared to do his own processing might benefit from the quality and look these films provide. It is by the way interesting to note that doing one’s own chemical processing is seen as archaic, but doing one’s one digital processing is a signal of professionalism.
Microfilms are very difficult to use for continuous tone photography as this is not the world they were designed to serve. Several companies have developed chemicals to cope with these emulsions and make them suitable for normal photographic use. One of the classical developers is the POTA developer, also known as Technidol for the Famous Techpan film from Kodak. There has even been a marketing campaign in the seventies of the 20th century where Kodak promoted the film for advertising work as an alternative to the medium format cameras.
Spur is one of the smaller companies that is constantly seeking to tame and improve these microfilms. Being a smaller player is an advantage as you do not need to have large stocks and can flexibly adjust production to new insights.
Their newest addition to the range is Nano Edge, specifically designed to improve definition of the Orthopan UR emulsion.
A companion product is Nano Grain, that is an improvement on Adotech. This test focuses on the Nano Edge developer.

Test conditions.


The film was loaded in my M7 with the Elmar-M 3.8/24mm as the taking lens. As previously noted, this lens easily captures 100 lp/mm with high contrast at medium apertures. The lens was set to an aperture of 5.6.
The test chart is the familiar bar-line device. There have been some comments that this type of chart is not representative of the real world scenes one normally takes pictures of. It is true that a test chart with alternating black and white lines is a quite simple target. An extended subject consists of many details with different shapes, sizes, brightness and contrast. Every detail produces its own diffraction pattern on the sharpness plane and the final image is a composition of overlapping diffraction patterns that can reduce contrast and sharpness. It is very difficult to find a reliable test pattern that can stand as a proxy for this complicated diffraction pattern. The solution is of course the MTF analysis, and the cut-off frequency of the MTF graph is also the maximum resolution of the imaging chain.
If you use a bar-line pattern with deep black and white lines, the relevance to practical photography is indeed small. One can cope with this problem by using a dark grey-light grey pattern which is more representative of the extended subject definition. I always test the film with a low contrast test chart as this is the most demanding condition for a test.
With an aperture of 5.6 there is already the beginning of diffraction effects. There is some misunderstanding about this topic. I will devote an article to this theme in the near future. For now we can say that the maximum resolving power in line pairs per mm depends on the wavelength and the focal ratio. For green light (wave length 555 nanometers) and an 5.6 aperture the theoretical maximum is 322 lp/mm. Every line occupies 1.5 micron or 0.0015mm. For an f/5.6 aperture the minimum size of the Airy disk is 0.0075mm. The diameter of the Airy disk is in itself not enough to determine the resolution limit.
The exposure time was measured with the Sekonic L-758D with flat receptor.
Development was according specs with the Heiland TAS developer machine to ensure consistent results. A calibrated thermometer monitored the developer temperature of 20 degrees.
Processing is simple: 7.5 minutes development, 30 seconds stop bath, 2 minutes fixing and one minute washing. The resulting negatives are extremely transparant: base plus fog is a mere 0.05 density.

Speed and dynamic range


The basic speed of the microfilm is about ISO6, but with suitable chemicals it can be enhanced. The speed of ISO20 (better would be EI20) of the Adotech formula is acceptable for most types of images, but the negatives are slightly thin, at least below the values that the Zone system stipulates. The new Nano Edge has a practical exposure index of 12 (Nano Grain has the same value).
The dynamic range of the Nano Edge developer is very impressive. Up to 12 stops can be effectively used. See the graph below.


SpurNano


It is better than Adotech and Nano Grain and has a very good overall density. The highlights are well separated, but extensive over exposure will block the high lights. On the other hand the shadow recording is excellent and the best I have seen in recent times for this type of film.
The speed of EI/ISO12 may seem a bit low, but remember that this is about the same sensitivity as the original Perutz Fliegerfilm in the olden days of the Leica camera. This speed coupled with modern high speed Leica lenses is quite useful for most ambient light situations and with flash it is easy going. The nice point is that you are never forced to use small apertures and you say within the optimum range of the high definition Leica lenses.

Resolution.


The Nano Edge developer has been optimized for acutance effects and should in theory deliver improved definition. I have to say that I was very surprised to see under the microscope the value of 200 linepairs/mm, the highest value I have ever noted in high definition photography. This number represents the just detectible difference between light and dark lines and it will be lost in printing. But even if you allow for image degradation during the printing process, the resultant value of 160 to 180 lp/mm is a record. You will not always need such a high resolution, but the clarity of the image and the clean edges at lower resolutions bring a new level of imagery to hand held shooting. The combination of the new 1.4 wide angle lenses from Leica on a film loading camera body with Orthopan film would approach medium format quality in the art of the snapshot.

Grain.


The grain pattern is very fine and invisible at magnifications to 15X.

Conclusion.


A film with 200 lp/mm, no grain, good density, 12 stops dynamic range and low speed for high definition photography is a stunning proposition even in current photographic world saturated with digital technology. Where digital technology goes to not so useful extremes in speed (who really needs EI 100.000?), the emulsion technology sets priority in high definition. The new Spur developer is a very welcome addition to the AgX photography. Precision cameras with the best of optical lenses and loaded with microfilm could find a new life.
The next part will compare this film/developer combo with the M9, now with as a target an extended subject.