Well, I should have qualified that statement with an "often." Certainly, if you test and know what your results are going to be, and if you understand the principles behind the terms well, then pushing and pulling are hardly sloppy guesswork.
Too often the terms, especially "pushing" get used without any idea of what they really do. Some think film is like digital and that you can just ratchet the ISO setting up and down at will, albeit with the inconvenience of changing development times, and magically get three stops more speed out of a given film, or deal with an ultra-contrasty subject, etc. Likewise, "pulling" gets used to magically enhance shadow detail but the associated reduction in development is often completely unnecessary.
If you know you're underexposing and losing shadow rendition and compensating for underexposed highlights and expanding a three- or four-stop SBR to an overall contrast that's easier to print, then, by all means, call it pushing
It's just that "push" and "pull" get bantered around a lot as panaceae for dealing with difficult lighting conditions/SBRs in lieu of better understanding of what's going on.
Don't get me wrong, I don't think the Zone System is anything but a simplification either. It is, however based on a basic understanding of the underlying sensitometry and tone reproduction principles (and it has that visualization thing going for it too
).
Best,
Doremus
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