The above scale is very approximate. Please don't threaten me for misrepresenting a divination, yeah?
There are only so many possibilities out there. Tone and light allow precise options, because they’re limited. That’s good. You can do away with a meter at times.
First, the difference between black and white objects in the same light is always 5 stops. If a white card in sun reads EV 15 (500 c/ft2), a black card in the same light reads EV 10 (10 c/ft2). That’s a fact, anywhere.
Second, any object in sun is 2 stops darker in the shade. Take the white card into the shade and it will read EV 13 (100 c/ft2).
How do you use this?
Let’s say I’ve got a forest scene on a cloudy day. Wet pine bark reads EV 9 (5 c/ft2), the forest floor reads EV 11 (25 c/ft2). This is a common situation for me. I’ll expose at 1/10 (1/8 with a modern shutter) at f16 (or equivalent). The tree bark will print without manipulation on Zone IV, the forest floor on VI. There’s a little sky, and some very black crevices in the bark and under some rocks. So depending on how it prints, the picture may look good as is. Or it may seem too gray and heavy, so it may need higher contrast in printing. Before I even take the picture I look ahead to the print.
(Anyone can do this. It’s the same as knowing how to cook. There’s nothing mystical or supernatural about it. And remember, the print isn’t all that important anyway if you see the subject powerfully. No ‘fine print’ ever saved dull seeing, though many have tried . . . )
Sun and shade situations are a little different. Let’s take the same scene in sunlight. Patches in the forest floor are EV 13 (100 c/ft2). So I know the same exposure will give me Zone VIII for the sunlit bits. It’s printable.
Extreme situations – The foregoing assumes an ‘open’ situation; that is, the trees above me are bare, and most of the skylight is falling on the scene. If I’m in a pine forest with dense overhead cover, the tree bark may be 1 c/ft2, and the needle strewn floor 5. Now when a patch of sunlight hits the forest floor, the situation is extreme: there’s too wide a brightness range.
If you want detail in the tree bark, and detail in the sunlit patch, you’re in trouble. If you place the tree bark on III, the sunlit patch is on Zone IX. With my film and developer, it will be blocked – no detail; a blank, white-gray.[1] If you want detail in the sunlit patch - Zone VIII, the pine tree bark is Zone II – a dead looking gray, no detail.
And this situation isn’t all that extreme. In dense cover, the difference could easily be higher – placing the tree bark on III might result in a Zone X or XI sunlit patch.
(This is why Fred Pickers MPD – maximum printable density – idea was suspect. That MPD idea assumes that all situations are ‘open’ – that no extremes exist. It also assumed that everyone used Tri-X and HC-100 like he did - and that everyone took the same pictures as he did. Ja? Placing the highest value on Zone VIII and taking the picture would probably ruin our pine forest picture. We could lose the crucial tones we need if we don’t think.)
What Decision?
So what do we do in our extreme pine forest? Well, with my materials[2] I’m stuck. Reducing the development time will drop the low values into nothingness – in fact the entire negative will look far too thin unless I give 3 or 4 stops more exposure – impractical. So . . . I can use a blue filter if I packed one. Or I can wait until the sun goes behind the clouds if there are any, or come back when it’s cloudy. That’s the standard ‘zone system’ answer (easy to teach).
A more telling point is this: not all elements in this picture are equal. The tree bark may be what the picture ‘is about.’ In that case it doesn’t matter – emotionally - if the high values are blank and without detail. Likewise with the sunlit elements: if you see them as a strange glow in a gloomy void, then the dark pine trees become unimportant. If – if – you make the right emotional decision, the compromise won’t matter. See – that’s harder to teach.
Emotional decisions are difficult to make. Many photographers can’t make them. The world abounds with too many ‘fine prints’ of very commonplace subjects; my eyes glaze over. But someone like Eugene Atget's work is magnificent because most of his emotional decisions were bulls-eye correct. What about his print quality? – some of those prints are pretty awful! – vignetting, scratches, plate clamps showing, bleached high values, blurred motion. It doesn’t matter does it? Not one bit. Vestal said, “[o]nly weak pictures need perfection. Strong ones can stand considerable flaws.”
Still, in our pine forest, what’s the technical decision? If you don’t know exactly, that’s fine. Take the picture anyway. What if you’re not sure about your emotional decision? Don’t worry about it. If the picture turns out badly, so what? - there are plenty of other good ones out there. And it might just turn out fine. If you’re free and open and receptive; there are enchanting moments, beautiful elements – everywhere!