I'm in the process of trying to figure out the metering on my manual 50 f/1.7. I'm using the M mode on my K20D and using the green button to set the initial shutter speed. I saw a post the other day that mentioned the "Sunny 16" rule so I thought I'd try it out. Using f/16 at ISO 200, this guideline should put me at a speed of 1/250 (closest to 1/200). I found that's a bit underexposed, and that 1/180 seems to be the proper shutter speed with this lens. I hit the green button to see if it would set it to 1/180 rather than 1/250, and to my surprise, it set the shutter to 1/20. I tried various compositions, and the green button takes me to the 1/15-1/30 range. I stopped down to f/8 and found similar results. Here are a few examples (taken in full sun at round 1:00pm):
f/16, ISO200, 1/20 second (this is the speed the green button set)
f/16, ISO200, 1/180
f/8, ISO200, 1/30 second (this is the speed the green button set)
f/8, ISO200, 1/125
Why would my K20D's green button be setting the shutter so low? There's no exposure compensation, and I tried center-weighted and spot focusing, both of which had similar results.
Thanks,
jeff