So...for example...I meter a highlight in the clouds...find it to be in Zone zone 8. It meters f/11, 1/500 at ISO 200. Zone 8 is three steps away from Zone V, which should be 18% gray. The setting for camera based on this reading would be to adjust my settings 3 stops lower?
Remember: whatever you measure with an incident light exposure-meter, it gives you a reading that will result in that reading
printing out as if it were taken from an 18% grey card, i.e. in zone 5.
So: you pick one convenient area of your subject to meter (e.g., your clouds). This places them in zone 5, but
you decide (before pressing the shutter-button) they REALLY belongs in zone 8. Zone 8 is 3 stops ABOVE zone 5, so to get your proper exposure for your clouds, you need to
open up (brighten them) 3 stops above the meter-indicated exposure. The other zones in your exposure will then fall into place "automatically". (Simple, really)
I meter another spot, considered to be in Zone 2. When metering it, and if I have correctly assigned the zone, then it should be three stops away from the midtones. Determining the proper exposure for midtones, I would raise the reading three stops to Zone V. If I have properly placed my highlights and shadows in the correct zones, then both readings, after adjusting them, would be approximately the same.
Am I understanding this correctly?
No. Again, (as for the clouds), your meter indicates a zone 5 exposure (this time for the shadows). Your shadows need to be in zone 2. If you expose for the indicated exposure value, they will end up in zone 5. Therefore, you need
to darken them by 3 stops; i.e. close down the aperture by three stops, in order to place them into zone 2. Again, the other zones in this, new, exposure will fall into place "automatically".
Of course, it helps if you have some understanding of what "
the zones" are.
Really, all this is very simple in actual practice...just try it.
Personally, I find it works very well for my film cameras: especially old manual RF and SLRs, using external lightmeters.
Chris Weston sets all this out very succinctly in his book
"Exposure", AVA Publishing (
AVA PUBLISHING - Part of the AVA Group, Switzerland), 2006.
BTW, I am currently reading my way through
Adam Ansel's book,
"The Negative", where all this is set out in great detail. (However, you don't really need ALL that much detail to start using it)
