--- Bob Walkden <[EMAIL PROTECTED]> wrote:
> Hi,
>
> ...
> Now, I can't find the back-up for my claim about AEL
> and IDM, so I may
> be talking complete balls, but there was a good
> reason for Pentax not
> putting AEL on the LX. They didn't just forget about
> it.
>
> ---
>
Certainly not, as the LX metering system is really
well-thought. An M.L. does not make much sense in the
LX and I think it's for a good reason (hope I got it
right):
The LX measures light in two different ways:
-- For the viewfinder indication, the LX measures the
light that is reflected from a secondary mirror onto
the metering cell (this value is stored in the camera
CPU).
-- During the exposure, the LX measures the light that
is reflected from the film surface (or 1st shutter
curtain). This value is not stored in the camera CPU
(the LX measures the amount of light which is in fact
accumulated during the the time of exposure).
These two metering modes could result in quite
different values, even when the camera is pointed at
exactly the same scene. A memory lock would have to
use the measurements of the light that is reflected
from the secondary mirror. Thus toggling between
'M.L.' and automatic would lead to somewhat be
unpredictable results:
- the component of diffusive light might be higher for
light reflected from the film compared to light
reflected from the secondary mirror (this particularly
makes a difference when light sources are within the
frame);
- reflectivity of film emulsions might differ from
that of the secondary mirror and among each other.
- measurement from the film plane considers changing
light intensity during exposure;
Shooting with fixed EV values should done in manual
mode. In metered manual, exposure adjustments are made
generally based on measurements from the secondary
mirror.
The shutter speed indicated in the viewfinder gives
only an approximation to the automatically chosen
speed. The manual clearly states this.
Hope this is more or less correct.
Alexander
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