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Olympus AF
Yesterday I did the usual bokeh testing for an Oly (PRO) lens.

I haven't done many such tests on MFT (for obvious reasons). However, I did notice once again that Olympus doesn't AF meter at max aperture - while e.g. Sony meters at the set aperture (usually at least).

I didn't check it formally but Oly appears to use something like f/2.8 or f/4 here (at least on the E-M5 II). That was during the "cat eyes" test scene where I used faster aperture settings. I noticed it because I set the aperture to X and the disc size increased massively on the actual image.

What could possibly be the reason for such an approach? It feels rather stupid to me because you lose the ability to check the DoF (there's a DoF preview button like on a DSLR).
It can't really be the amount of light. Because the AF data is based on the main sensor image, the data is, in turn, dependent on the basically constant exposure (in normal scenes) - the camera constantly adjusts the exposure for the live view image after all.
Chief Editor -

Doing all things Canon, MFT, Sony and Fuji
Big Grin 
I'm using EM10 iii with 12-40 f2.8 most of the time. I haven't noticed that. Is it possible to adjust the aperchure so the camera  better focus on  light sources?
I see MFT gear getting some love from you?
Sony does not AF wide open with bigger apertures? And behaves differently with different lenses in this area too.

For a constant live view feed you have to deal with a limited exposure time range you can use for the live view video feed, and with the slow-ish read out of the sensor too. Also, beyond that exposure time limit, often cameras "simulate" the exposure in live view so that within the exposure range the camera can use during live view the user does not get an overexposed or underexposed image which would not at all show the actual exposure outcome of a image capture. Canon calls this "Exp.Sim" or "Exposure Simulation", which itself has a little bit limited range too (so if you use very odd settings you still can get a too dark or too light live view feed).

Too early here (GMT +!) to theorise more on what Olympus actually does and why.

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