Archived posting to the Leica Users Group, 2006/12/08
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Steve It sounds as if you're going to underexpose by a stop. What result are you looking for? Walt Steve Barbour wrote: > Walt and others... have you shot C41bw 400, at 800 with normal > development? Results? > > I see this now as advantageous, have never done it, but I plan to > try.... > > thankjs, Steve > > > On Dec 8, 2006, at 6:41 AM, Walt Johnson wrote: > >> I think I'll start shooting all my Tri-X at 666 ISO. BTW has anyone >> noticed the change (years ago) from ASA to ISO appears useless? >> >> Henning Wulff wrote: >> >>>> Doesn't it have something to do with logging rhythms. in .3 >>>> increments? >>>> >>>> Henning Wulff wrote: >>>> >>>>> At 10:29 PM +0100 12/6/06, Philippe Orlent wrote: >>>>> >>>>>> I was just remembering my ISO scale on the back of my MP: >>>>>> 50-100-200-400-800- etc. >>>>>> >>>>>> But the zones in between are divided in 3 parts. >>>>>> >>>>>> So between 50-100: 50/3=16,7 >>>>>> Between: 100-200: 100/3=33,33, which would put 160 at 100 and 2/3ds >>>>>> Two full stops under brings us at >>>>>> 400 and 2/3ds >>>>>> Which is 400 + (800-400)x2/3= 666,7 >>>>>> >>>>>> I may be wrong, but it looks like Leica logics to me. >>>>>> :-) >>>>>> Philippe >>>>>> >>>>> >>>>> ISO is not continuous. It's only defined for the discrete >>>>> progression (from 100 to 3200) for 100, 125, 160, 200, 250, 320, >>>>> 400, 500, 640, 800, 1000, 1250, 1600, 2000, 2500, 3200. >>>>> >>>>> No numbers in between, ie, there is not 'ISO 300' or 'ISO 666'. >>>>> >>> >>> ISO combines the old ASA and DIN scales, and makes the measurement >>> methods and ratings equivalent. DIN was logarithmic while ASA was >>> arithmetic, with 400 ASA = 27DIN, 320 ASA = 26 DIN. For every step >>> the ASA took an arithmetic step, and DIN took a logarithmic step. >>> Different measurement methods meant that there wasn't a complete >>> equivalency, but then they got together and came out with the ISO >>> method and scaling, which allows for both an arithmetic and >>> logarithmic scale. So now the old 400 ASA is approximately ISO 400/27. >>> >>> Both systems jump in discrete, defined steps with intermediate >>> values undefined. >>> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >