Who remembers Kodak Super XX film?
I loved it as a kid – it was the predecessor to TriX, though I used it long after it was discontinued. That would be in the 1970s. The main reason I used it was that Kodak still made it in bulk 35mm rolls for cinema use, so you could pick up fifty or a hundred feet (the latter good for over 700 snaps) for a song. It’s speed was 250 ASA, the grain sharp and tight, like TriX and the speed could be easily pushed to 500 ASA with a bit of extra time in the developer.
And 250 ASA (or 25 DIN to the Europeans amongst us, the Britain of my youth, of course, not being a part of Europe any more than it is now) was a speed that was just right. Not so fast that you had to stop down excessively, but fast enought to permit short, blur free shutter speeds. Your lens, as often as not, was set at f/4 or f/5.6 where pretty much every lens is at its best, and affords just the right degree of background blur to liven things up a bit.
DIN? Deutsche Industrie Normen or something. Only the Germans could concoct a system so perfectly ridiculous that you had to be a Doctor or Professor (which every German is, of course) to understand it. You see, it was a logarithmic system such that an increase of 3 represented a doubling in speed. So 24 was twice as fast as 21, which happened to be 100 ASA. As for 25 DIN being 250 ASA, well, let me tell you that much time with a scientific calculator was needed to figure that one out, my memory of logarithms not being what it once was. Go figure. Still, it kept enough consumers confused for long enough that camera stores (remember those?) thrived. A confused consumer is a repeat customer, often as not.
So, in a strange flashback to days of yore, I find myself setting the ISO (what?) on my Canon 5D to 250, often as not. Right there between Regular (100) and Fast (400). Then of course there is Very Fast (800), Super Fast (1600) and Bloody Fast (3200). Come to think of it, why don’t manufacturers simply mark the speed dials S, R, XX, F, VF, SF and BF? Now those I can understand.