Hi all, You're C&C is certainly welcome on the following. After getting a new E-M1 ( which now has Firmware v2.0), MMF-3 adapter & used ZD-300mm for wildlife work, I tried to figure out the "best" AF settings to use for action. Read many threads (likely from some of you) & did lots of shooting. My favorite testing was shooting RC model planes - great fun & great practice. All this practical testing(?) left me thinking that settings for Frame Rate, Release Priority, Release Time-Lag, C-AF Lock made no discernible difference in AF speed. But this testing involved so many variables, I couldn't be sure these results were meaningful. After some thought & trials, a relatively simple test procedure has confirmed my original conclusion - these settings yield no AF speed improvements that can be measured in some practical way and are very unlikely to provide any advantage in real shooting. So we can all relax. While all of the tests I report here were done w/ the 43 ZD300mm f2.8, tests w/ the m43 M.Z75-300mm @ 300mm showed that these settings make even less difference for such a slow focusing lens. The AF for the M.Z zoom is only about half the speed of the 43 ZD300. Before any of you get irate w/ me, there is an important caveat to these results. The standard deviation for these speed tests is 1/5th of a second. Not bad by human standards but still this is a coefficient of variation of about 25%. It is possible changing these settings makes an improvement that is too small to detect w/ the simple tests I've done. It may also be possible that the new Oly Pro lenses w/ faster AF speed will yield small but detectable improvements when settings are changed. But as you will see the old ZD300 is no AF slouch. Regardless, as the many debates about whether using the Vivid mode improves AF speed showed, there is such a thing as an AF placebo affect. These tests are sensitive enough to rule out all but the smallest practical benefits of different settings. And this set of tests address only raw AF speed for initial focus acquisition. It is possible some of these settings could improve the ability of the AF to stay focused on a moving target after initial focus acquisition or as interfering objects move into the frame - I'll try to test that later. The test procedure is simple. The target is the old Air Force resolution chart at 40' + an iPad running a stop watch app. I'd trigger the shutter on the 10's or 5's & both count the # of frames before acquiring focus & note the stop watch time captured @ focus. Exposures were ISO 500, SS=1/1250" & around f4. To test the affect of Release Time-Lag settings, I simply shot single frames of the target 20 times each using both Normal & Short Time-Lag w/ the lens already focused on the target in S-AF mode w/ Release Priority Off. The speed results & variation were identical for both settings: mean=0.20 sec. & Std. Dev=0.063 sec. This total time includes both how long it takes me to press the remote button & how long it takes the camera to fire as the clock hits say 1 min. & 10 seconds. Not bad in real world terms. Next were the tests of C-AF initial focus acquisition speed. For these the E-M1 was set to Sequential @ 6.5 FPS, 9 AF targets. The lens is first pointed at a target about 80' away & half-press the shutter button to get that target in focus. The the lens is then pointed at the chart/iPad @ 40' & the shutter button is pressed when the clock hits a 10. In 1 set of shots, I also tried initially focusing on a spot 50' away before shooting the chart @ 40' to see if closer pre-focus provided an improvement in final focus acquisition speed. The number of frames & time until target is in focus (@50% mag viewing) was recorded. For C-AF tests, at least 10 tests of each setting were completed. Here's a typical sequence of such shots where focus was acquired in the 2nd shot @ 0.70 sec & the AF settings are shown in the shot w/ Release Priority On: [/url]_A210316 - 2014-10-21 at 12-14-34 by tradesmith45, on Flickr[/IMG] [/url]_A210317 - 2014-10-21 at 12-14-34 by tradesmith45, on Flickr[/IMG] [/url]_A210318 - 2014-10-21 at 12-14-34 by tradesmith45, on Flickr[/IMG] The end results w/ various combinations of AF settings were: Mean time to AF acquisition for all tests=0.86 sec. & 2.6 shots The range for all the tests was 0.89 to 0.82 sec. which is far smaller than the random variations of testing. Std. Deviation = 0.20 sec Here's a complete list of things I tested that provided no affect on AF speed: Release Time-lag - Normal & Short Display Frame Rate - Normal & Fast C-AF Lock - Off, High, Low Closer Pre-focus @ 50' vs 80' I found only 1 setting that made a reliable difference in C-AF mode. Having Release Priority Off reduced the number of captures w/o focus but had no impact on time to acquiring focus @ 0.82 sec. So turning C-AF Release Priority to On only fills you card faster w/ out of focus shots. EDIT: Please note that the AF speeds found for the ZD300mm were measured with the Focus Limits switch set for 6m to infinity. Hope all this is helpful to you.