Fredrik Eriksson wrote:
> Your D90 can do this too, though the image is displayed on the back LCD 
> instead of in the viewfinder.

Yeah. The Sony I have does both, which is nice when it's bright out. And (as 
I said) you can tip the LCD on the Sony so you can shoot from other angles.

> The main drawbacks of not having a mirror are that you cannot have a 
> through-the-lens optical viewfinder or phase-detect autofocus.

Sure. I'm just not sure what the benefit of an optical viewfinder is over an 
LCD viewfinder.  The Sony seems to do a better job of autofocus, but then 
I've had years to play with it and learn its quirks, so maybe phase-detect 
is a better method.

> Actually, there are two mirrors. The big one is indeed semi-transparent. 
> Most of the light is reflected up towards the viewfinder and exposure 
> meter, and the rest goes to the smaller mirror which reflects the light 
> down towards the autofocus sensor. Linear polarisers can mess with 
> exposure because they can alter the proportion of light that reaches the 
> exposure sensor.

More precisely, they'll screw up your half-silvered mirrors' reflections. 
The linear polarizer is exactly messing with reflections off transparent 
surfaces (i.e., prisms), which is exactly why you wear them when fishing or 
driving in a car with glass windows that have reflections in them otherwise.

I didn't find the circular polarizer to have any noticable effect on my 
photos, tho.

-- 
   Darren New, San Diego CA, USA (PST)
   Insanity is a small city on the western
   border of the State of Mind.

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