metering 18 per cent gray cards

[leica ron]

Roger, first of all "Thank You", it was yours and Frances's book on LF and MF Photography that got me into 4x5.

 

Here's what I understand, I'm not preaching to anyone:

Anyways, back to the question at hand. As far as I understand it, an 18% gray card metered for a given environment (e.g. mid-afternoon, slightly overcast in September) and a negative exposed as per the meter reading will give a reasonable negative when developed as specified by the film manufacturer. This negative will then allow enough latitude for the lighter (Zone VI-VIII) and darker areas (Zone I-IV) to allow a reasonable print to be made.

 

If you metered with an 18% gray card and your scene was snow, your negative will be exposed such that any non snowy white areas have been exposed for long enough to record detail on the negative.

 

If you metered the snow and didn't add a stop or two over your meter's reading, then the negative will not have detail in the darker areas.

 

So as far as my understanding goes, the meter is calibrated to expose an 18% gray on a standard film.

 

My use of the Zone System is heavily based on this single point of reference. I point my spot at an area close to 18% gray if it's there and place this at Zone V. If I see a lighter area, maybe I put it at Zone VII or VIII. This is a more systematic approach to using an 18% gray then using your brain to add a stop or two.

 

Alternatively, I meter for the darkest area I want detail in and then place this at Zone III.

 

I might be way off base, but it seems to work for me ....

 

Cheers !

p.s. the scale on the Pentax Spotmeter really helps me make these decisions to my satisfaction. When I shot 35mm, I had no idea what my matrix-metering system was assuming ....