a thought on the zone system

[vicmortelmans]

I was contemplating the zone system again and I was wondering how many zones are covered by reflective capacity of object (thus: excluding shadow effect) and how many by shadow effect.

I did the experiment and took two sheets of colored paper: one white and one black, and positioned them in identical light conditions. (Spot-)metering the white paper gives a read-out that is ~4 stops higher than the black paper.

Also consider the fact that some object in direct sunlight is ~3 stops brighter than the same object in shadow (or back-lit) (sunny 16 vs. shady 5.6).

If you add the two, one can see that a scene containing objects with black and white surfaces, that are partly lit by sunlight and partly in shadow, spans a range of 7 stops in total, from a black surface in shadow to a white surface directly lit.

Adam's zone system provides room for 11 zones: 0-X. Zones 0 and X are just collectors for everything that's out of range (no detail), and zones I and IX is for the first faint discernable detail. Leaving zones II to VIII for the actual image information... hey, that's 7 zones in total! Seems to match perfectly to the number of stops the a scene will typically span!

Groeten,
Vic

 

[vicmortelmans]

I only considered outdoor lighting by the sun.

If you consider indoor conditions, things are different.

Objects lit by a single light bulb loose 2 stops in brightness, when the distance from the bulb is doubled. So take e.g. two objects in a room, one at 25cm from the light source and one at 2m from the light source, the first will be 6 (!) stops brighter than the latter. If the objects themselves have a contrasty texture of 4 stops, this scene will span 9 zones and will be hard to catch for normal film. This doesn't even take into account shadow effect, as shadows from a single light source are pitch dark and will stretch far beyond the 3 stops of 'sunny shadow'.

Similar when using flash: the object at 1m from the camera will be 2 stops brighter than the object at 2m from the camera. But in this case, the shadow effect is eliminated, as all shadows fall behind the subject.

Groeten,
Vic

 

[vicmortelmans]

and of course, even outdoors, you can have deeper shadows than 3 stops, e.g. under a dense tree or a shelter.