Please test this and let me know how it works for you. Here are some preliminary findings, that may help those having trouble metering with M or K lenses. I have not tried screwmount.
The general consensus is that the camera underexposes with faster apertures. I have found that the camera exposes "properly" at f8, and error increases as you deviate form this fstop.
NB: My definition of proper is to have at least some of the scene exposed in the final quadrant of the histogram. Consider me a conservative ETTR-er.
Try this: set the compensation for 0. Set the lens to f8, and CENTER WEIGHT for middle grey. I have had a terrible time spot metering with M lenses at small apertures.
Now, every full f stop you move towards the maximum aperture (in my case, 1.8), move the EV compensation +0.3 and vica versa.
So (I am using the K55mm 1/1.8 as a reference):
f8 - 0
f5.6 - +0.3
f4 - +0.5
f2.8 - +0.7
f1.8 - +1.0 (this one is approximate).
The histograms were very similar. Note that this formula works in 1/3 or 1/2 steps, but 1/3 is more accurate (works for 4 out of 5 stops, 1/2 only works for 3/5 stops). I prefer 1/2 for speed, myself.
As we move past f8, metering seems to be very inaccurate, and it best done compensated from f8.
Any criticisms of my findings would be greatly appreciated. I have tested this method with both an Takumar Bayonet 80-200 f4.5 and SMC K 55 1.8.
Last edited by paperbag846; 08-19-2010 at 04:08 PM.
Reason: I have adjusted these values as the the original data was skewed to the left.