AFMA results - Conflicting values

[neuroanatomist]

Good point! I'm not that "bright" 7.8 EV from a 500W spotlight.

When I read the manual initially, it recommended having at least 10 EV. Low light leads to inconsistent results in part due to the longer shutter speed required (vibration reducing sharpness, but variably). Vibration can even be an issue with shorter shutter speeds. When I started testing, even with my 12 EV, I'd get failed runs sometimes - the setup was on the main floor of my house, hardwood floors, and me or my kids walking around was the issue. I moved the setup into the basement (concrete slab floor) and the testing was much more reliable.

I use three 150 W gooseneck lamps, so I actually use less total wattage. But...remember the inverse square law. My lights are positioned about 12" from the target.

I have a question, or two, about the Focal software. Does it step through the adjustment range while it is running to find where the image is sharpest? Reason I ask is that I see in the graphs that it covers such a wide range that I wouldn't expect to see from a camera body. The other question is what do the numbers of the Y-axis actually represent as the measured quantity?

Yes, it iteratively steps around the range from -20 to +20, and uses predictive algorithms to refine the values tested. The plots I posted are from a very early version of FoCal (IIRC, the first version to offer reports because I have just screenshots from older versions) - I would not read anything into the Y axis. But newer versions offer an image quality test, so I suspect the numbers may be more meaningful now. Even with my older tests, it's no real surprise that the 5DII has higher Y-axis values than the 7D, right?

[Steph]

I use three 150 W gooseneck lamps, so I actually use less total wattage. But...remember the inverse square law. My lights are positioned about 12" from the target.

Alright, I'll try to setup something in my garage then with the 500W spotlight reeeally close to the target. I'll post other results and let you know how it went.