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Re: [OM] 18 0rey Card

Subject: Re: [OM] 18 0rey Card
From: Lars Bergquist <timberwolf@xxxxxxxxxx>
Date: Sat, 25 Apr 1998 08:27:24 +0000
Wrote Konrad Pizzuto:

>I've heard about the 18 0rey card and that camera metering systems
>calculate the light received from an object as that coming from
>something of 18 0rey reflectivity.  I'm not sure I've got the whole
>concept right... could someone be so kind as to explain the whole
>concept... possibly in relation with the OM-10 metering system as an
>example.
>
>If I got things right, say you hold up an 18 0rey card in a certain
>type of light, and get a shutter speed reading for a particular
>aperture, does that mean that if the light does not change, and you take
>ALL your photos in that particular light, with fixed shutter and
>aperture settings the exposure's will be spot on?

The industrial standard is that all exposure meters are calibrated for a
subject with a reflectance of 18%. This includes incident light meters.
So a reading with a reflected light meter aganst a Kodak Gray Card does
give the same result as metering the incident light. This is very
dependable. It is in fact always right (this would be a very long posting
if I were to explain why). The card is a bit unwieldy, so a better way
is to get a decent hand meter with the little opal white dome for metering
incident, and bringing it along. Take a walk and compare this meter and
method with the built-in reflected light meter in your OM. You will
learn a lot about exposure!

Note that incident or grey card metering is never misled by overly dark
or light parts of the subject, by light sources such as the sky in the
picture field, etc. So with reversal film, the critical highlights are always
correctly exposed. (If there is enough interest, I could expound at lenght
on this).




Vänliga hälsningar/Best regards
Lars Bergquist
Välkommen till/Welcome to ...
<http://www.bahnhof.se/~timberwolf/>



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