Archived posting to the Leica Users Group, 2006/12/08

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Subject: [Leica] Math, now bwc41 at 800
From: kididdoc at cox.net (Steve Barbour)
Date: Fri Dec 8 17:25:20 2006
References: <7.0.1.0.2.20061206152403.027b4508@infoave.net> <23C63C29-1E1D-43D6-A946-45C580F2326E@pandora.be> <4577300C.7000108@mcclary.net> <F04C2DAF-1C77-416C-ACC7-72A31E62F94F@pandora.be> <p0623090dc19e3edfaa21@10.1.16.133> <4578A515.7040506@waltjohnson.com> <p06230914c19eb640e40f@10.1.16.133> <45796BA5.1080109@waltjohnson.com> <C191A03E-177F-47CF-82F5-833737DBB103@cox.net> <45797B5B.4020903@waltjohnson.com> <82c9dd70612081532r8ad7e6eva845220b1787fc7@mail.gmail.com>

On Dec 8, 2006, at 4:32 PM, Eric Korenman wrote:

> TCN  does best at ISO 320.
> It gets way too thin at ISO 800.
> just 2 cents from shooting hundreds of rolls of the stuff.

  so far my experience bears this out...BW400,  thin at 800....Steve


>
> Eric
>
> On 12/8/06, Walt Johnson <walt@waltjohnson.com> wrote:
>>
>> 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
>> >
>>
>> _______________________________________________
>> Leica Users Group.
>> See http://leica-users.org/mailman/listinfo/lug for more information
>>
>
> _______________________________________________
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> See http://leica-users.org/mailman/listinfo/lug for more information


In reply to: Message from images at InfoAve.Net (Tina Manley) ([Leica] Math Question)
Message from philippe.orlent at pandora.be (Philippe Orlent) ([Leica] Math Question)
Message from harrison at mcclary.net (Harrison McClary) ([Leica] Math Question)
Message from philippe.orlent at pandora.be (Philippe Orlent) ([Leica] Math Question)
Message from walt at waltjohnson.com (Walt Johnson) ([Leica] Math Question)
Message from walt at waltjohnson.com (Walt Johnson) ([Leica] Math Question)
Message from kididdoc at cox.net (Steve Barbour) ([Leica] Math, now bwc41 at 800)
Message from walt at waltjohnson.com (Walt Johnson) ([Leica] Math, now bwc41 at 800)
Message from faneuil at gmail.com (Eric Korenman) ([Leica] Math, now bwc41 at 800)