In another thread a user commented that the DA*300 with HD1.4x combo did not AF-C well so I decided to do an AF test with K-3 this morning at a nearby bike path to check continuous Af with subjects advancing toward camera at good clip.
Tried a few combinations and found these to have best results for this appplication:
AF-C, Spot, First Shot Focus Priority, Continuous Action -Focus Priority, Hold Status Off
Lenses tried - Bigma 50-500, DA*300, DA*300+ HD 1.4x TC
Exposure mode used: TAv, f8, 1/500 (In retrospect should have used faster shutter speed as I think overall IQ suffered a bit from motion blur)
Overall the Bigma yielded most % in-focus shots in continuous bursts.
Both the DA*300 alone and with the 1.4x HD TC yielded similar % in focus shots, a bit lower than the Bigma.
I suspect this may be due to the SDM motor not reacting as fast to AF commands from the K-3 as the Sigma HSM system.
The DA*300 alone or with the 1.4 would sometimes lose a shot or two focus in a sequence, where the Bigma was more consistent.
Most common loss of focus was as the riders got closest the DA*300 with or without the 1.4x , perhaps as the changes required were just too big for the SDM to keep up with.
The naked DA*300 yielded the sharpest photos, while adding the 1.4x gave a small drop in IQ, with the Bigma close behind.
All combos seem usable for this application on a sunny day, as the light drops the DA*300 alone will be best option.
Here are representative sequences.
Bigma @500mm 44 shot sequence, all in focus (not all frames fit in the LR4 display window.)
DA*300 33 shot sequence, 2 shots out of focus after it picked up the cyclist.
DA*300 + HD1.4x 46 shot sequence, 6 shots out of focus.
I used a monopod to help keep the lens pointed accurately, I am sure some mis-focus was due to my moving off the target in spot mode.
I tested 9 point center bias and 9 point auto, but sometimes the focus would lock on another nearby object, it worked best if I tried to keep the cyclist in the center.
Last edited by crewl1; 09-27-2014 at 02:47 PM.