A number of years ago I was at an "International" meeting of Biological/Biomedical Photographers where DR Martin Scott indicated that with Kodachrome (which had the "tightest' of all processing requirements) the BEST way was to read/meter a 'white with texture' and 'place that value in "Zone VIII+1/3' which is usually within 'about 1/3 of a stop of an incident meter reading.
I now 'use that method for ALL my LF B&W films.. my reasoning is that the hominid eye is first 'drawn to the 'lighter' areas for 'information' in that area before seeking fine details in the 'shadows'.
Now... before y'all try and 'shut me down' might I suggest that you 'give it a try' before telling me I'm an idiot and I don't know what I'm talking about... but I've used it for years and I'm more that just 'satisfied' with the results.
Ken
Yep, that's probably the best way to expose Kodachrome or any other transparency film. Notice that you're basing your exposure on the least-dense area of the film (the whites in transparency film are the least dense). Note also, that basing your exposure on a shadow value for negative film is the same thing, in essence. For transparency film, there's not much contrast control, so the shadows get sacrificed in favor of texture in the high values in contrasty situations. With B&W film, we don't have to settle for this. Still, using a similar metering method isn't necessarily going to give you bad negatives.
The late Fred Picker of Zone VI Studio fame used to recommend placing a high value (Zone VIII iirc) and forgetting about the rest when shooting black and white. This works pretty well, actually, in all but the more contrasty situations, especially if you rate your film at half the box speed, which he routinely did. Where this method breaks down is in situations with large subject-brightness ranges. In these cases, basing your exposure on a highlight value that's many Zones away from a shadow area you may want detail in ends up underexposing said shadow. Think dark interior with a window and a bright daylight scene outside. If you base your exposure on the scene in the window, that dark interior will end up featureless. The ideal way to deal with this situation (with negative film) is to meter the interior and adjust development (or somehow otherwise deal with contrast) for the high values. One can save the shadows if one recognizes the situation as very contrasty and adds exposure to the meter reading (basically a high-contrast exposure factor) to get adequate exposure in the low values. If the negative is then developed "normally," one would hope that the normal development was not too aggressive, and that one had enough other contrast controls (VC paper, etc.) to get the print made.
Fred also didn't use a lot of different development times (N, N+, N-), but just two, N and N+1 1/2; he felt that contraction developments always yielded poor prints. So, you can bet that his development times were on the short side. He'd meter and place his highlight value, make two identical negatives, develop one normally and one at N+1 1/2 and then print the one that worked best. As I said, this works well in the majority of situations. It's basically what I do when shooting roll film; I just add modify it by adding additional exposure for contrasty situations, thereby reducing the risk of dumping the shadows.
So, Ken, I'm not surprised that that a similar method has worked for you well over the years. Just realize that it's a simplification that works in the majority of cases, but not all. Basing negative-film exposure on a shadow value
always ensures adequate shadow exposure. Even if one develops everything at one developing time, the resulting range of contrasts can be fairly easily dealt with with printing controls provided that one arrives at a standard developing time that places both extremes (high- and low-contrast scenes) in the printable range. For those of us that shoot sheet film, tweaking development time a bit for scenes that are more or less contrasty than normal is easy. For roll film users, less so. If you want to modify your method to compensate for loss of shadow detail in really contrasty situations, just overexpose a stop from your meter reading when the contrast is great. That will increase your chances in those trickier situations.
Best,
Doremus
Face slap! 
Stupid me! 
I have been doing exactly that for several decades with great results! Now I will have to stop doing that just because Witold said I am wrong! 
Woe is me! 
