FrankS said:
Joe and Vince are correct in saying that we can recognize the lighting situation, and Bill is right in saying our eye/mind can't "meter" light levels directly.
Thanks, Frank, yes, that's what I mean.
The eye & mind cannot measure lumens. Neither is the amount of light available on a sunny day constant all over the earth minus the poles.
What is possible is what is constantly demonstrated by those who say "Well, I am able to correctly set exposure by eye," and then they proceed to do just that.
However, what they have done is rely upon approximations and the latitude of their recording media to guess without serious error. Their exposure is no more under their control than a single use camera's.
If one wants to let the 'close enough' maxim take charge, then one can certainly guesstimate exposure, set hyperfocal distance focusing, and point-n-pull. That's certainly appropriate for some photographic situations, too.
But I submit that if one is willing to simply get the exposure close enough and not take creative control of it, then use the meter built into most of the cameras these days and set the thing on AE. It certainly won't slow you down, and it will probably guess better than you can most of the time.
If one wants to take creative control of exposure, then a different methodology is called for.
In neither case is guesstimating exposure really an ideal solution. It will work, but it seems to be useful only in displaying a perverse pride in one's ability to get a dart on the dartboard at all, let alone near the 10 ring. We buy the best lenses, the best cameras we can afford, we agonize over film choices and how best to process and scan, and then we 'eh, who cares' the exposure.
Seems a trifle odd to me.