Quote: If that's the best you can do as an argument for an "uncrippled mount", then I want a beer dispenser in my camera. [...] What is it an uncrippled mount does again? Is that the thing that makes your viewfinder so dark you can't see?
I just wanted to show that the "I/we don't need it" argumentation is not a good one. As a final consequence, photography as a hobby would e.g. not exist or we would all be limited to pictures from mobile phones. The advantages of an uncrippled mount are e.g. discussed in
the corresponding thread. And no, "the thing" does not influence the brightness of the viewfinder. The aperture coupler mechanically tells the body, by which amount the lens is stopped down. This information unfortunately is ignored by current Pentax DSLRs. Thus, you have to meter via the green button (which in contrast then darkens your viewfinder) if a lens is not set at the "A" position. See also:
Features and operation of the crippled mount.
Quote: In my experience the optical preview lever does work properly. I have no real idea whether while the OPL actually closes the aperture and meters reality vs. the Green Button merely emulating the same (which would be a challenge since the elctronics cannot know which lens is actually mounted), but I have excellent results with K lenses metering with the Optical Preview Lever.
The green button provides a "stop down metering", which is not accurate:
Test procedure: An image of a white area was taken with an A-lens and a K-5 at several f-stops (x-axis), the grey scale value of the image then was determined with Photoshop (y-axis).
Blue curve: Lens set to A, aperture value set in camera (which would be similar to the usage of an uncrippled mount).
Red curve: Aperture value set at lens, usage of green button (note the deviation from the blue curve and/or a constant value: the fluctuations correspond to about two [!] f-stops)
Test of the reliability of the "green button" metering
De-crippling the K-mount will lead to an increased and/or more reliable functionality with all lenses possessing an aperture ring.
One could use the aperture ring and just shoot away. This would work with any K, M, A, F, FA lens.
Automated metering, more exposure modes, and flash capability (currently fires at full power) would be possible even with K/M lenses (or lenses not set at the "A" position).
The usage of bellows and extension rings would be simplified.
One would have a "three wheel camera": Set aperture at lens, time and ISO with the two e-dials.
The green button is a less-than-ideal solution, where a better, more accurate and simple alternative is available at low cost.
Using a good tool is better than using a flawed one, even if both do their job.