Those photos are a perfect example of where an incident light meter shines.
(pardon the pun).
When confronted by such extremes in brightness levels, the only thing you
can be sure of is that the fuzzy logic in the cameras will be fooled. The
exposure might go high, it might go low and in some cases it might just
decide to average out the entire mess and call it a day. Regardless, you can
be pretty sure that the resulting exposure will be way off.
With digital, it's even worse, because with saturated colors as presented in
nature by flowers, sunset skies and those cheeky primary colors at a
playground, if you get even close to the top in exposure, you'll saturate
(blow out) a color channel which doesn't show up on the histogram.
With an incident light meter, you substitute the scene with an "artificial
subject". By measuring the light falling on this substitute subject (the
white dome of the meter), you are assured to get a proper exposure of the
real subject as its reflective value relates to the midtone calculation of
the incident light meter. Therefore, if the real subject's reflectance is
two stops brighter than midtone, if you set the camera's exposure to what
the incident meter tells you, the photograph will capture the real subject
exactly two stops brighter than midtone.
But that's not why you called...
When confronted with such extreme brightness ratios in a scene, and you know
the camera meter is going to choke, you must approach the exposure
calculation in a systematic manner:
1. Determine what is the subject to be properly exposed? (in an extreme
contrast scene, pick one part of it, not the entire scene).
2. Visually estimate the reflectance (brightness) of that subject in
relationship to midtone.
3. Meter the subject or substitute that subject for another subject with a
known reflectance (brightness). For example, you hand. If you use the palm
of your hand, open up one stop to compensate for the fact that the
reflectance of your hand is one stop brighter than midtone.
4. Adjust the camera's exposure and take picture.
The above is the general procedure for working with digital JPEGs or slide
films where THE most critical thing is to maintain proper exposure
relationship to midtone. When working with color images, if this
relationship to midtone is not maintained, then the entire scene is
over/under exposed, regardless of how well preserved the highlights or
shadows are.
However, when working with digital raw and/or B&W, specifically the Zone
System or variations therof, you are less concerned with midtones, but more
concerned with the extremes. With B&W, the old adage of "expose for the
shadows, develop for the highlights" and when printing "expose for the
highlights, contrast/develop for the shadows" applies. Midtone exposuring in
B&W is perfectly valid, though, when photographing people, events or other
things like that where you wish to have a churn-n-burn system which can be
used for high-volume printing.
This is where spot-meters and the OM-3/4 metering system applies. If you
want to do the substitute routine easily enough, in manual mode, just spot
meter your hand and adjust the aperture/shutterspeed so the exposure reads
one-stop high. That's it. But when you have a subject that is way high or
way low, you meter that subject and literally just move that dot to the
point in relation to midtone that you want. The beauty of the OM-3/4 system
is that it allows you to take multiple readings which you can move around
en-mass to keep all of them within the latitude of the film. Or, in the case
of the photo of the flowers with the large expanses of black in the frame,
if you really want those areas to go black you take a reading of that area
and move that dot so far down on the exposure scale that it falls below the
acceptable exposure range of the film or sensor.
AG (The Dome) Schnozz
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