FAB -
In short, no.
The OM-1's meter uses two CdS (photo-resistive) cells on either side of
the eyepiece, "looking" into the back of the prism just like you do when
you're focusing. They register the light level at the focusing screen.
There's no space to insert any sort of optical device to concentrate
their focus on the center of the screen, and simply covering them with
some sort of Waterhouse stop (a plate with a hole in it) would only have
the effect of reducing the amount of light that reaches the cell, giving
an erroneous reading.
Those cameras with true spot metering capability usually use amplified
photo-voltaic cells which are manufactured with a large "average" zone
around a small "spot" zone in the center of the cell. Light from the
film plane is then focused onto the cell. These two zones function
independently of one another, giving one reading for the very center of
the frame and another for the rest of the frame.
Spot meters that _do_ use CdS cells usually have an optical arrangement
to provide the spot effect - like using a telephoto lens, as mentioned
elsewhere.
Franklin A. Berryman wrote:
>
> This is a technical question probably best answered by John H., but here goes:
>
> Is there anyway to modify an OM-1/1n to reduce the area the meter reads so
> that
> it spot meters? As I understand it, the meter is center weighted and reads
> off
> the pentaprism. Anyway to reduced the angle of view so that it meters off a
> just the microprism area?
>
> Here's hoping...
>
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