Just picked up a Pentax m 100mm f4 Macro with dental scale and decided to give it a test run in the yard.
1st under natural light on Helicoid K for 1:1 (clover blossom).
Next I tried 1:2 with diffused flash (bee).
Then I tried to lay stealth in some bushes but could never seem to lock focus before subject skittered away.
Took a while to figure out the problem.
DO NOT let the cat join you on that Macro outing.
Really like this lens, seems to produce as well as my copy of the Tamron 90.
Picked up this lens to try with IR as the Tamron 90 macro suffers from hotspots. It performs stellar with the Tiffen 87.