Originally posted by Canada_Rockies My vote is also for the SMC-M 100/4. The one I have happens to the the "dental" version - it has extra scales on the lens extension for use with the tube and close up lens that came with the dentist's kit. I have neither.
I find the stand off distance of the 100 to be good, and with the K10D, it will be even better, because of the (in)famous crop factor. I can be half as far away again from that 3 inch dragonfly.
you should try it with the 1.7x AF TC. it gives you a measure of AF when you are close with manual focus, and combined with the 50mm or so of focus extension built in to the lens, can give you past 1:1.
that should help you chase dragonflies a little better!
I have also had some fun reciently putting a close up lens on my 135 F2.5. So far just in a local greenhouse, but I will play a little more when the bugs thaw out.