Archived posting to the Leica Users Group, 2013/10/03

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Subject: [Leica] Auto ISO
From: jhnichols at lighttube.net (Jim Nichols)
Date: Thu, 03 Oct 2013 15:22:07 -0500
References: <D081BEA2-0FD5-4700-95E9-F125B060C7E1@acm.org> <CAAsXt4OyjVt4N5Cx4fgjYkbSN5Lo37iVPXC=O_3FppC62BFBCA@mail.gmail.com> <80F9701439F20347874CE5E4E03C22E9CDE2ACC3@WhizzMAIL01.whizz.org> <0171C3C9-D25D-4852-BBAA-03695B57B4B6@acm.org> <CAFfkXxtu5PQd7fwSWE9Pmij-CgfwL0-1EpU+wygd64HmZ=N4EQ@mail.gmail.com>

Many of us have faced that challenge, Sonny.  Here is an image from many 
years ago, camera and technique forgotten, showing the ravages of 
macular degeneration that left "Poo" blind.

http://gallery.leica-users.org/v/OldNick/Cigar+Box/Macular+Degeneration+Begins.jpg.html

Jim Nichols
Tullahoma, TN USA

On 10/3/2013 6:25 AM, Sonny Carter wrote:
> First argument I ever got into in the LUG was over the black cat thing.  At
> the time, I think I was the only person with a black cat.  It depends on
> the circumstances.
>
> http://www.sonc.com/belinna_guards.htm
>
>
> On Thu, Oct 3, 2013 at 1:34 AM, Herbert Kanner <kanner at acm.org> wrote:
>
>> That's where you use exposure compensation. Shoot a white swan: increase
>> exposure by compensation or any automatic system will want it to be gray.
>> Shoot a black cat and decrease exposure for same reason.
>>
>> Herbert Kanner
>> kanner at acm.org
>> 650-326-8204
>>
>> Question authority and the authorities will question you.
>>
>>
>>
>>
>> On Oct 2, 2013, at 12:00 PM, John McMaster <john at mcmaster.co.nz> wrote:
>>
>>> I cannot see how it would? There I am putting an exposure in for a
>> silhouette and the camera thinks "that's underexposed" so ups the ASA 3 or
>> 4 stops....
>>> john
>>>
>>>> -----Original Message-----
>>>>
>>>> I'll have to read again, but I don't think AutoISO works on pure manual
>>>> mode...
>>>> Would you double check also?
>>>> Thanks Herb,
>>>> Bob
>>>>
>>>>
>>>> On Tue, Oct 1, 2013 at 9:30 PM, Herbert Kanner <kanner at acm.org> 
>>>> wrote:
>>>>
>>>>> I thought a few words about how this function operates on Leica, at
>>>>> least on the M9, might be useful to y'all, since the Leica Manual is
>>>>> not the clearest on this subject.
>>>>>
>>>>> Let's start with an understanding of the relationship between the
>>>>> three
>>>>> parameters: ISO, f-number, and shutter speed. We are used to thinking
>>>>> of exposure having one degree of freedom for a correct exposure. That
>>>>> is because we are used, from years of experience with film, of
>>>>> thinking of ISO being a constant. You can't change ISO in the middle
>>>>> of a roll of film. So, for any situation, there is one degree of
>> freedom for a
>>>> "correct" exposure:
>>>>> you change shutter speed, you have to change aperture, and vice versa.
>>>>> Hence, for the little all-electronic cameras where both the aperture
>>>>> and shutter are under computer control, you can choose the aperture
>>>>> (aperture preferred), or you can chose the shutter speed (shutter
>>>>> speed preferred) and the camera choses the one you didn't chose. You
>>>>> all know this; I'm just being pedantic.  Oh, then these idiot cameras
>>>>> have "programmed" mode where the camera chooses both based on
>>>> some arcane set of rules. That's for bozos.
>>>>> Now, lets look at the Leica. The camera can control the shutter, but
>>>>> it can't control the aperture. So the only automatic mode would appear
>>>>> to be aperture preferred. Ah, but the ISO is under the control of the
>>>>> camera's computer. It is now a third variable: it can be changed at
>>>>> any time. So, Leica in its wisdom invented Auto ISO. Now we have two
>>>> degrees of freedom.
>>>>> That is, we can pick the values of any two: say ISO and aperture, and
>>>>> now the shutter speed is determined. Thus, on the Leica, we now have a
>>>>> way of doing shutter speed preferred: set the shutter to the speed you
>>>>> want, set the aperture to the f-number you want, and the camera will
>>>>> pick an ISO that gives the correct exposure. So, what happens if you
>>>>> set Auto ISO and aperture preferred on the M9? You will be in s
>>>>> situation similar to program mode in a point and shoot. The camera
>>>>> will chose both the shutter speed and the ISO value. I took a few
>>>>> shots at three consecutive stops on the dial, and the shutter speed
>>>>> sat at 1  /150, perhaps not what I would want with a 90mm.
>>>>>
>>>>> If you set a shutter speed and an f stop with Auto ISO, everything
>>>>> works fine as long as the ISO that gives "correct" exposure is in the
>>>>> available ISO range. And you can use exposure compensation. What you
>>>>> lose is any information about exposure in the viewfinder. What
>>>>> information could that be? The ISO the camera selects, of course.
>>>>>
>>>>> One warning: the little dot and triangles used for manual exposure
>>>>> setting seem to be meaningless with Auto ISO: just ignore them.
>>>>>
>>>>> Herbert Kanner
>>>>> kanner at acm.org
>>>>> 650-326-8204
>>>>>
>>>
>>> _______________________________________________
>>> 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
>>
>
>




In reply to: Message from kanner at acm.org (Herbert Kanner) ([Leica] Auto ISO)
Message from rgacpa at gmail.com (Robert Adler) ([Leica] Auto ISO)
Message from john at mcmaster.co.nz (John McMaster) ([Leica] Auto ISO)
Message from kanner at acm.org (Herbert Kanner) ([Leica] Auto ISO)
Message from sonc.hegr at gmail.com (Sonny Carter) ([Leica] Auto ISO)