[Leica] Auto ISO

[richard at richardmanphoto.com (Richard Man)]

Auto ISO is normally best used with auto-exposure. As Herb said, a 3rd
variable to control the exposure.

With the M9, you can set the max/min range, whether it's lens dependent
(kicks in when it's 1/focal length) or an absolute number you set.

On the M9, it works in both auto-exposure and manual exposure modes.
Remember the meter is still mainly a semi-spot meter.

I use it most the time for snapshots, even on manual mode. I set the max to
ISO 1250. Most of my prints are not being blown up so this is fine.

For landscape shot, I set the ISO manually.


On Wed, Oct 2, 2013 at 12:02 PM, John McMaster <john at mcmaster.co.nz> 
wrote:

> You are not alone ;-) Well I use it on snap cameras where I have less
> control/concern but not on the Leica's
>
> john
>
> > -----Original Message-----
> >
> > I think I'm the only naysayer on this, but I would never use auto ISO.
>  It
> > makes no sense to me!
> >
> > Leo Wesson
> > www.leowesson.com
> >
> > > On Oct 1, 2013, at 23:30, 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.
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>



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