substitution http://www.adorama.com/alc/taginfo/substitution Article: The substitution metering method.A useful exposure tweak <p><span style="font-size: small;">When using the substitution method, you replace an object within the scene with an object of known reflectance, such as a Kodak Gray Card and take a reflected-light meter reading from this object.</span></p> http://www.adorama.com/alc/article/8574