Archived posting to the Leica Users Group, 2000/08/04
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Here's something a little weird. I just got back my Canon 50/1.5 LTM (1951) from cleaning. At some point I got it into my head that it was time to see if the transmission was higher through a 7/3 Sonnar type than other constructions. I had already tested it against a clean 50/1.2 Canon and determined that there was no speed difference (in terms of meter reading), or at least one within half a stop. Interestingly, with the same target (beige wall), the results were (with the meter set to 1600) Canon 50/1.5 @f/2 = Between 1/250 and 1/500 sec Nikkor 85/2 @ f/2 = 1/250 sec M-Hexanon 50/2 @f/2 = 1/250 sec M-Hexanon 90/2.8@ f/2.8 = 1/125 sec This is not the way it's supposed to work - all of them should read the same (or as equivalents). Any ideas? It shouldn't be a huge difference like that because the Canon is single-coated and the Hexanon multi. If anything, the more modern glass should be brighter. I suspect the old Canon transmits more light, even stopped down, even without multicoating and LD glass. Or it's really a 1.2 and the f/2 mark is where 1.5 really is. ------------------------------------------------------------------------ Dante Stella http://www-personal.umich.edu/~dante