RalphLambrecht
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agreed
agreedI'm going to suggest a small change in word usage.
"over expose" tends to imply too much exposure.
"under expose" tends to imply too little exposure.
Both tend to imply a mistake.
For clarity, it is really helpful in these sorts of discussions to instead discuss actions - we decide to "increase exposure" or to "decrease exposure" and we usually speak in terms of numbers of stops.
And, when we compare the light reflecting off of various parts of a scene, we talk in terms of stops as well.
The reason to use a grey card is that it supplies a repeatable reference. The reflectivity of an 18% card is approximately the middle of what we encounter in real life. So if everything is calibrated correctly, if we meter off of a grey card (using the proper technique) then the image of any 18% tone in a scene will be recorded on the negative to a density that should print as a middle grey tone in a print, and the darker and lighter tones in the scene should print appropriately as well.
The reason we use a meter to gather information from the shadows, is twofold:
1) negative film has less room for error on the shadow side, and more room for flexibility on the highlight side. Accordingly, we meter the shadows to be sure we capture the important information there; and
2) not all scenes have a 18% reflectance in the middle. Some scenes are such that you want the middle to be darker. Other scenes are such that you want the middle to be lighter.
It is important to understand that with respect to the zone system, you don't meter to find the "darkest thing with detail". You meter the darkest thing that you want to have detail in your final output (usually a print).
Let me give you an example. I take lots of photographs in forested areas. There are lots of scenes there where there are dark shadows that I'm quite happy to render dark and free of detail in my prints.
If I am using zone system principles when metering, I'm visualizing the result I want in the print and then measuring the light reflecting back from the various parts of the scene. Those measurements tell me that if I adjust the camera exposure to place a certain part of the scene (the part where detailed shadows matter to me) at one level, the other parts will fall at other levels. My experience then tells me how the resulting negative will print in a straight print, and will give me a good idea how it may print if I also apply the printing controls available to me.
The zone system is a way of systemizing the following:
1) visualizing first, and then
2) accomplishing the vision.
It all comes back to the final output - the print.
In the case of the photo I posted up thread, the biggest advantage of using a spot meter would have been that I wouldn't have had to go swimming if I wanted to take some detailed readings from some of the smaller parts of the sceneSo is it safe to say that spot-metering will render you a more accurate depiction of what you envisioned?
Is that the advantage of metering the subject over a gray card?
2. In the very little experience ( a month or so) of being taught the zone system in a course, we were taught to expose for the "darkest subject you want with detail". Ok. Simple enough. Expose for the shadows/develop for the highlights.
3. My confusion lies in this: Why don't we always just use a gray card then? Why bother with finding the darkest thing with detail, shadow, etc? Or, are you sacrificing some of these zones by using a gray card in situations where it's just too difficult to get a proper exposure/reading? Aren't we trying to "get away" from the middle gray that the camera auto-corrected to exposure wise?
Beware of silly rubrics. This one is an extension of the "expose slides for the highlights and negatives for the shadows" nonsense.
You are not confused; you are far wiser than most photographers and most of the responses to questions like yours. Every scene should be metered correctly, or as you put it, to the grey card. The mark of a good photographer is to understand the light and what will and will not make a good image on film. If the scene has ten stops of range, it will not make a good picture and there is no way around that. We see proof of this every day with those god-awful, frankensteinesque d!&!+@l images where someone takes five different exposures and stitches them together in Photobox or Lightshop or whatever and is oh so proud of an image that looks so fake it would make you wretch.
Understand the scene as a whole. If there is a specular reflection, don't include it when you meter as it should look specular on the film. If you're metering bright snow or a pile of coal the meter will tell you to stop down or open up to get the detail your eyes perceive when looking at the scene.
ansel adams' The Negative is a confusing and not particularly well written book for me at least. I found Barry Thornton's Elements a far more user friendly and chilled read of many of the same concepts
Beware of silly rubrics. This one is an extension of the "expose slides for the highlights and negatives for the shadows" nonsense.
My confusion lies in this: Why don't we always just use a gray card then?
Why bother with finding the darkest thing with detail, shadow, etc?
Or, are you sacrificing some of these zones by using a gray card in situations where it's just too difficult to get a proper exposure/reading?
Aren't we trying to "get away" from the middle gray that the camera auto-corrected to exposure wise?
...and I have not done anything with the zone system beyond camera exposure. (i.e. no development times, printing, etc.)
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