Do all Pentax cameras use the same lens?

[mattdm]

Originally Posted by Mr Guy

What does "metering with the green button mean"?

With older manual lenses, in order to get an exposure meter reading, you have to press the green button (on K10D/K20D) or (I think — I haven't tried this) on the K100D which lacks the green button you pull the on-off switch to its depth-of-field preview position. This stops down the lens and takes a meter reading.

[Mr Guy]

Originally Posted by mattdm

With older manual lenses, in order to get an exposure meter reading, you have to press the green button (on K10D/K20D) or (I think — I haven't tried this) on the K100D which lacks the green button you pull the on-off switch to its depth-of-field preview position. This stops down the lens and takes a meter reading.

Thanks, that nailed two questions with one great answer!

The unasked question:
I haven't quite made it all the way through the Magic Lantern book I bought, but I was hoping at some point they'd tell me what that third position meant on the on/off switch that seemed to take a picture (but not really). I recognized it appeared to look the aperture fin things, but couldn't figure out what it was for and didn't know how to google "Weird circle symbol". It didn't occur to me that it was a preview.

Thanks once again mattdm, you've been extremely helpful as I've been trying to figure out my new toy.

[mattdm]

Yeah, so in addition to the metering, it also is (mildly) useful for getting a feel for the depth of field of your shot at your selected aperture — the little circle symbol is supposed to represent the aperture blades. A lot of new people see it as the "make the viewfinder darker lever".

It can also be set to provide a "digital preview", which is basically an image snapped but not saved. This is mostly useful when you have the LCD set to not display pictures automatically after each shot.