| Hello, and welcome!
Well, regarding the exposure problem, let's say it's related to the lens used.
For f/3.5-5.6 lens, exposure will be quite good.
But with fast lenses, you'll have a variable amount of underexposure...
- f/1.4 needs about +1 1/2ev
- f/2.8 needs about +1ev
and so on...
This is due to the fact that the focus screen does not respond in a linear way to the aperture of the lens...
You should have a direct relation between shutter speed and aperture (i.e. going from f/1.4 to f/2 should halve the shutter speed, going from say 1/1000 to 1/500).
But with the original k20 focus screen, this relation is not respected (going from f/1.4 to f/2 won't halve the speed).
Note : I'm talking about using actual, stop-down apertures.
For A lenses, the exposure is mesured wide-open, then calculated for the given aperture you want to use, so selecting f/2 will always gives half the speed of f/1.4.
BUT the wide-open reading will be underexposed by the 1 1/2ev mentionned above, so the lens will always underexpose, whatever aperture you're using.
Using an old lens (with aperture blades actually moving when you select an aperture on the lens), you'll see that closing one stop won't halve the speed.
You can lessen this behavior by using a LL60 screen (from the *ist line). They are fully compatible with the k10/k20, and lessen the discrepancies to the point where you won't really need to compensate the exposure anymore.
Regarding SR, I don't have any idea about it... |