Originally posted by audiobomber I RTFM but I'm still confused. I have my K20D set to allow manual aperture settings. If I take the lens out of auto aperture mode, and set the ring at a selected manual aperture, I'm getting erratic results.
In Av mode with the aperture ring on my FA 50mm set for f1.4, it didn't show the aperture before the shot (F---), but it took a photo at f1.4, 1/2000s. When I moved the aperture ring to f22, it still used f1.4, 1/2000s. In Program mode and mechanically set to F22, it took a photo at f2.8 and 1/1000s. I have a 28mm A lens that is doing a similar thing. No matter what aperture I set mechanically, it takes the photo at f4. I've tried P and Av modes. What am I doing wrong?
To use the aperture ring, you need to set the camera to "M" and press the green button after setting the aperture. The camera stops the lens down, takes a meter reading at the set aperture and sets the shutter speed accordingly.
My own experience with this is that the camera does a reasonable job of getting it right in bright light and moderate apertures, but it seems to run out of accurate metering range fairly quickly, so if you are stopping down a lot, or are shooting in dim conditions, you may want to either use a hand meter or check your review screen frequently.
Also, the way the aperture cam works was altered when they made the change from M to A (IIRC, A series and later is a non linear movement), and I don't believe the K10 or k20 is capable of giving a really accurate exposure with A lenses using the aperture ring.
I get very good exposures with pre A lenses, but the few times I have experimented with later lenses the exposure have been kinda all over the place.