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

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Subject: [Leica] Math, now bwc41 at 800
From: walt at waltjohnson.com (Walt Johnson)
Date: Fri Dec 8 06:48:45 2006
References: <7.0.1.0.2.20061206152403.027b4508@infoave.net> <45772DC5.3040508@mcclary.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>

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
>

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