There is a lot of reference to the use of light meters in evaluating lighting conditions to facilitate shooting in Manual Mode.
In the olden days, once the film was loaded, for any given lighting condition there were only two adjustments available. Shutter speed and Aperture. Of those two, for any given subject there is usually one which is of priority and as camera manufacturers introduced "automatic" mode they provided the user the ability to manually set one and let the metering system set the other.
Also in the olden days, there was no way to view the result of the selected exposure settings until the entire film developing process had been completed.
The many references to light meters and manual exposure would have us believe that there is something almost magical to be gained by this methodology under all conditions.
Digital cameras provide say 12 f stops of latitude, to use a term from those film days, and our aim is to place those 12 stops nicely within the range to best capture the luminance range of reflected light from the given subject. But what if it is beyond the capability of the camera? In that case we would be forced to accept a loss of detail in either the shadows or the highlights. Or both. There is one other variable over which we have control, you might say. True, we could provide more or less light as necessary but that is not really practical under many or most normal situations.
Shooting in a studio is of course a whole different set of circumstances but I am not talking about shooting under tightly controlled lighting conditions.
The point or question that I pose is, how, in all practicality, is there any advantage in setting ISO on a meter, selecting Aperture or Shutter speed as the priority setting, reading the appropriate metered F stop or speed and shooting the scene with those settings set manually OR simply setting ISO and "A" or "S" and having the camera instantly compute and set the remaining parameter?
Or better still, just setting "P" and monitoring the result.
Mr. Rockwell was unfairly lambasted for referring to "P" as "professional mode".
I agree with him if it was his little dig, which, to his amusement, so many bit, at all those people who think they can do better, or rather, be seen to be doing better and being a better photographer by not needing to rely on such amateurish stuff as anything automatic.
In truth, "P" is referred to as Program Auto which takes into account, and I can only speak of Nikon here, a whole lot more than some may have us believe.
The metering system in a modern Nikon is profoundly more sophisticated than the everything averaged down to 18% gray "dumb" light meter portrayed by some.
There are a great number of controls and combinations of controls available, and there are many which most people will never use.
The Nikon D3 was designed for professional use and it incorporated only those features required by a professional in order to get the "money shot". I refer, of course, to the type of subject affording little time and no second chance to get the shot. "Mr President, would you mind falling over again, I need a meter reading..." There are no bells or whistles. It is ready long before you are and it will always get the shot if used correctly. It is very rare indeed that setting "P" and releasing the shutter fails.
I am in no way saying that using external light metering and making careful accommodation of all things considered etc. etc. has no place but I fail to see the advantage in real terms of making photography more complex an activity than is necessary, especially if shooting manually is dressed up as being some sort of elite club to be revered by we lesser beings who happen to have a lean towards the practical use of technology.
Light meters and shooting manually does not magically expand the performance of your camera. All it can ever do is allow the photographer to stand up and take "credit" for some of the numbers on his photo's exif data.
As I said, shooting in a studio and all the control over lighting that affords is a different thing altogether but I am not referring to that.
Over to you….Rob.

Good grief, Rob. Are you trying to set a page record all by yourself? I've never seen one of your posts that long, and I have seen very few when you didn't skewer someone. Are you losing your touch or are you getting old? We're going to have to hurry to get that beer before one of us kicks the bucket because of old age.

Seriously though (as serious as we can get), I like my toys, especially my light meter and color temperature meter. The Sekonic doesn't tell me what I can do; it merely suggests what I shouldn't try to go. And my Sixti-color keeps me from coming up with pink locomotives and purple cabooses under all the crazy lighting in the museum. I still don't trust "automatic white balance" and a lot of other bells and whistles (not to mention toot, whistle, plunk and boom). Tell me, compadre, am I just getting to old for this stuff. Best regards. Bill