but from what i've read the Pentax 540 ain't that mechanically stable like some of our friends here who had tried it with the tupperware difusser. Not willing to pay so much for the Pentax name.
Had no choice but to pay $250 more for the (frankly...POS) pentax AF540. Sigma EF500 built felt impressive (I might even say it feels tougher than the AF540) and its so cheap... too bad the two EF500s I tested seemed somewhat unstable...after a few shots or a while it just FREEZES dead then had to power off and on again.