Originally posted by dlacouture 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...
That is the first time I have ever heard that the focus screen is why Pentax cameras underexpose. Where did you get that info? I've heard of some of the 3rd party ones affecting exposure but not the default Pentax one,
To the OP. The general consensus is Pentax choose to have things slightly underexpose to save blown highlights. Everyone has a slightly different opinion on how much Pentax underexposes, I find in most situations that exposure is pretty accurate and the underexposer to be minimal.
I'd say learn your camera and lens and make the determination if your combo has the need to dial in exposure compensation for the type of shooting you do. You may find that you never really need to.
Oh for your second question. Yes the 2 second timer disables SR. The reason for the 2 second timer is that it actually raises the mirror for those 2 seconds before it releases the shutter. This is used in situations where your shutter speed is SO slow that the mirror slap would actually cause motion blur. With shutter speeds that slow you really have to be on a tripod, hence the camera shutting down SR.
John