SPUR DSX is a black and white document film in 135 format, 36 exposures, nominally ISO 50. It is a technical emulsion adapted for ordinary photography, and there is exactly one reason to buy it: resolution up to 600 line pairs per millimetre, a figure no conventional camera film reaches.
How the picture looks
Grain is effectively invisible (an RMS value of 1.0 is about as low as it gets), and detail survives to enlargements where the lens gives up before the negative does. With SPUR's own Dokuspeed SL-N developer the film holds a 14-stop exposure range — deep shadow to bright highlight with nothing lost at either end.
What to shoot on it
Landscape and architecture from a tripod, reproduction work, macro, anything destined for a large print or a maximum-resolution scan. ISO 50 plus a tripod is a deliberately slow way of working, where a frame takes time. It is not meant for reportage or handheld shooting.
How to shoot it
One requirement the maker states outright: a normal continuous-tone picture needs SPUR's own Dokuspeed SL-N developer. In an ordinary developer a document film delivers extreme contrast — black and white with almost nothing between. Budget for the developer alongside the film, or the results will disappoint. The emulsion is orthopanchromatic, with limited red sensitivity.
Processing and scanning
Hand development in Dokuspeed SL-N to the times in SPUR's datasheet. The base is thin and wants care when loading onto a reel. It repays that: scan at your scanner's maximum optical resolution, or the purchase is wasted — most of what is on the negative will simply go unread.
How it compares
Its nearest relatives are other document films on the same stock, including the Agfa Copex Rapid that DSX is made from. The usual "sharp" films — Ilford Pan F+, ADOX CMS, Kodak T-Max 100 — either resolve less or demand the same kind of dedicated developer. If you do not need the resolution ceiling, an ordinary ISO 50–100 film is easier in every respect.
