The Pentax 6x7 metered prism is not a spot meter, not even a center-weighted meter. It meters the brightest point of the whole view to light gray; so in order to get an accurate metering in contrasty scenes, I cover the brightest area over the lens and aim to where should be light-to-medium gray. It isn't really a good meter, sometimes better trust your perception, or just use a handheld lightmeter.