The same way it knows the correct exposure time when
the light changes. All the MX knows is the amount of
light entering the lens wide open and where the
follower on the lens is set. As aperture ring is
changed the follower changes position and the MX knows
how much less, (or more if you're opening the
aperture), light to expect at the time of actual
exposure. It's more or less a simple matter of
addition or subtraction, (OK so that's a gross
oversimplification but good enough for the basic
concept). The camera's internal light meter doesn't
have to know the magnification. It's only if you are
using an external light meter then the __photographer_
will have to know the magnification to compensate for
the difference in exposure.
--- Frank Wajer <[EMAIL PROTECTED]> wrote:
> Hi,
>
> how does a manual camera like an MX know what the
> correct exposure time is
> with
> for example a macro lens. As the magnification
> increases the eff. f-stop
> increases
> so exposure should be longer right? But the MX
> doesn't know the current
> magnification so how does it do correct exposure
> time. Only thing I can
> think of
> is that a macro lens doesn't have an automatic
> aperture.
>
> Frank
>
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