Much has been written about exposure control in photography. What I've learned has been by experimentation, reading, practice, and by accident. What I am writing today is the same in theory as what has been written before by the pioneers of photography, but this will be my attempt to simplify the explanation.
Okay, last November I was driving down the freeway and happened to notice a landmark that I knew was there, but never really noticed it in detail before. The Jefferson Barracks National Cemetery is very large, and also very beautifully laid out. When I noticed this from the freeway I made a mental note to eventually get over there and shoot a roll of film. At the time I knew exactly the camera I would use too. I had a vision in my mind of something panoramic, and what better to pull that off than my Kodak No 3-A Model A camera that I converted to use 120 film yielding 6x14 cm negatives? Fast forward to present day and I made the trip with camera in tow.
Before I get into this too far, I should mention that something else I have been wanting to do is to regurgitate "Zone Control" using my expressions and experiences. With this in mind I grabbed a digital camera to take along. A lot of whats written about Zone System shooting has examples with explanations, however, I've never found one with color photographs. I know, seems nuts that I am reverting back to color, but we see in color, or at least I do. Sure would be cool if my headlights had a little switch to go B&W only, but mine just don't have that feature. So, I took a dSLR with me to shoot the scene how my eyes were seeing it, and from that hope to progress into Zone placement for B&W film. Oh, I also took along my trusty Minolta Spotmeter F. It's a 1 degree spotmeter, and I love the thing.
Okay, in the color photograph, with the ISO set to 200, and set to aperture priority, the camera selected 1/60th on the shutter, and the resulting image looks pleasing and exposed well for average metering. I selected 200 ISO since that is the film I would be shooting later, and also shot in aperture priority as I lean towards the long DoF of f16 or more. In this case it was set at f22.
When I am visualizing a scene, I try to focus on the features that really matter to me most. This is where there are many forks in the road. Everyone has their own tastes, and preferences here. For this scene I was visualizing the grass as something I definitely wanted placed in Zone 3. I prefer this to be dark, but with plenty of detail. From there I frame the rest of the lighting scene.
After converting the color image to B&W, it's easy to see how plain and boring the average metering is. After being converted, the grass has landed almost in Zone5, while the blue of the sky has landed in Zone 8 and the clouds in Zone9. What to do? Focusing again on the grass, if I stop down two stops I will have the zone I want for that part of the scene, but the sky will still be lighter than I like. There are other things that can be done to control lighting and the tones recorded on B&W film though. Filters are an excellent help here. Since I know I am working in the two zone range of adjustment, that makes me think of a heavy yellow filter. The filter factor is 2.5 stops, and would accomplish more for this scene than would an aperture adjustment. The #15 yellow filter significantly darkens the blues in the sky, and also provides separation between clouds and the blues. Visually, the effect this has on the light spectrum as recorded by the B&W film, is the effect more like a three stop adjustment, which is where I want it for this part of the scene. The last photograph is what was recorded using the Kodak No 3-A Model A camera with a #15 Yellow filter, shot at "I" 1/50th, and f22 on the aperture, and was just about exactly as I had visualized this scene for using B&W film.
Shooting Zone System is actually simple once practiced a little. This is especially true with modern cameras with good lenses having aperture ranges up to f22 or f32, and with modern shutters that typically range from a few seconds up to 1/1000 or faster. One little challenge I have with some of my gear is the limitations on shutter speeds. The Kodak No 3-A Model A I was using has three settings for the shutter - I B T. Instant is about 1/50th, Bulb, and Time are just that. The good thing about this camera is the aperture range is from f4 up to f128! Another challenge is that the original lens has no provisions for filters. As seen in the photo of the camera nose, I made up a couple adapters to use with my oldies. This really helps control lighting with filters on these old cameras with limited shutters. The adapter is nothing more than a Kodak Series VI 1 1/4" adapter ring that I epoxied to a modern filter ring size adapter (49mm~58mm). It slips on the end of these old lenses and uses modern ring filters.
Hopefully in the near future I will be able to get out and make some captures that demonstrate Zone control using development times; Normal, push, and pull.