My test procedures and methodology as follows:
1. A K-1 and DA50 F1.8 combo was selected and used for the test, i.e. same gear setup as claimed by one of the OPs for improved performance. ;-)
2. AF was carried out in a fairly lit room in about 300 lux, two objects were placed at about 1m and 3.5m respectively and AF was made on the two objects to and fro alternatively. This was repeated for more than ten times and the AF sound was recorded:
(Click to Enlarge)
3. Measurbated the AF starting and completion times, right before the AF motor started to move and before the AF confirmation beep was sounded:
4. Input the times into an Excel table and calculate the AF time required (in second) for ten times of AF operations and take the average time and get the results. Here we go:
Left table contains the results with FW version 1.52 and the right one are those with FW version 1.51. Indeed, I cannot see any real and significant difference between the two. So, it's what psychological effect of people strikes again, case closed! :-D