When I made the switch from digital to large format film, I realized that there was so much more about photography that I needed to learn. Quite frankly, I had become lazy with digital. I could leave the camera in evaluative metering, bracket the shots, and capture enough tonality to come up with the ideal exposure in Photoshop. Although this technique certainly works, it was not very rewarding.
It was only about a year ago that I shot my first frame of velvia on a 4×5 large format camera. In that year, I have learned so much. My first photo was of a beach scene with a rock in the foreground, and lots of slick mud that reflected light. I used my Sekonic 358 to meter the scene (no spot meter). The resulting photo was overexposed because the meter could not take the reflected light into consideration. The rest of my exposures that day were very dark. Something was very wrong with my metering abilities.
On my last trip, I was faced with some rather difficult to meter scenes, and ended up with some very ideal exposures. This gives me confidence that my metering skills have greatly improved.
My meter of choice is a Sekonic 558. This is a very ideal meter because of the combination of spot and incident meter. During full daylight, or when there is a dominant light source (reflected light) the incident meter readings are near perfect.
When shooting seascapes, an incident meter reading will be accurate so long as the sun is above the horizon. As soon as it drops, a spot meter is mandatory to obtain a proper exposure.
When using my spot meter, I start by obtaining a base reading. I will often accomplish this by taking a reading of either a gray card, or an average of the brightest highlights, as well as the darkest shadows that I want to maintain detail. Next, I view how the tones fall in the scene. So long as the most important highlights are no brighter than +2, and the most important shadows are no darker than -2, the exposure should be ideal.
I now have a pretty good feeling for what values the various tones should have in a given scene. This certainly comes with practice. Here are some examples of some different scenes, and how I have learned to meter them.
Mid-day light This is of course the easiest to meter. So long as there is a dominant light source, an incident meter will give very accurate results, I place the meter parallel with my subject so that it captures the light that falls on the subject. Sometimes I will switch to a spot meter, use the same exposure setting in average mode, then make sure that the tones fall in the +2 to -2 range.
Back-lit Leaves In this situation, I use the incident meter. I place the meter in the sun, and face the dome upward toward the sky. This has given me very accurate meter readings in situations where there are back-lit leaves.
Seascapes Here on the Pacific, I always shoot sunsets (into the sun) for my seascape photography. So long as the sun is above the horizon, I find that a simple incident meter reading is a good starting point. My seascape photos are usually rather wide angle, and incorperate a lot of foreground. By aiming the incident meter upward, it catches the majority of the light that is falling on the foreground subject. This is usually a mixture of both sunlight and reflected light from the sky. A Grad filter will then be necessary to help darken the background. After I have established a base exposure from the incident meter reading, I will then switch to spot metering, and evaluate the tones in the scene. I will make sure that any important shadow areas are no darker than -2, and the brightest areas are no brighter than +2. If the highlights read +3 that means that a 3 stop grad filter will return the sky back to neutral tone, which will hold a lot of color.
As soon as the sun sets, the incident meter is useless. At this point, I will obtain my base exposure from a gray card. I stand facing the sun, and hold a gray card out to my side, parallel to the horizon. The gray card will receive reflected light from the ocean/sky, and provide a good base exposure. I will then put that exposure value into memory, place the meter in average mode, and evaluate the tones to make sure that the scene has proper exposure. If I notice that the foreground is too dark, I will re-meter the scene and repeat the procedure.
Slot Canyons with Near-by Reflected Light This is a very easy to meter scene. When the light source is a canyon wall that is illuminated by sunlight, it will cast a nice soft glow of light into the scene. So long as your entire scene is bathed in this light, a simple incident meter reading next to your subject will provide an ideal exposure reading.
Slot Canyons with Distant Reflected Light In these situations, incident meter readings are worthless. Also, gray cards are worthless. This is because the light that I am standing in is not the same light is illuminating the subject. Imagine a narrow corridor with a light source near the end, but out of view. That light source is bouncing light off the canyon walls. The best way that I have found to meter these scenes is average two meter readings, the brightest highlights, and the darkest shadows that I care to maintain detail in. After I average the two readings, I can then look through the spot meter, and see where the tones in the scene fall. At this point, it is a matter of interpreting the meter readings.