Originally posted by P. Soo That's true Steve. But some people will get so frustrated that they will put away the non-A lens assuming it is unusable, unless they consult the experts in the Forum.
Or unless they consult their user manual.
I know, the user manual is a little terse and the information not easy to find, but it is there. After all, the "experts" on the forum learned it from somewhere. Fortunately, they are kind enough to patiently walk hundreds of users per year through the intricacies of working the stop-down metering system resulting in many happy Pentax users.
FWIW, to address your original question, the "Aperture Enabled" custom setting with "off" as the default has been a feature of Pentax SLRs since at least the *ist film camera in 2003. The default setting is puzzling to those of us who use non-A aperture ring lenses, but not so puzzling to those who own A-series and FA-series lenses with the "A" setting and who also use them on cameras that support the aperture ring for Av or manual modes (most K-mount Pentax film cameras). In that case the aperture ring is frequently off the "A" position when the user is expecting it to be "on".* Before the *ist, crippled mount ZM/MZ series cameras behaved badly when paired with a non-A situation with little feedback to the user. Much wasted film and spoiled photos were the outcomes. Having "Aperture Enabled" as a setting with fail-over being "no exposure" was much preferable. I agree that removing the setting option and having the camera default to F--- is probably a reasonable alternative in the present environment.
Steve
* I sometimes flex my FA lenses onto my '80s vintage film cameras and have been bit by this use case.