EF first (and 2nd) tests

 I'm satisfied by my initial tests with the Viltrox EF-L adapter and Canon 100-300/4.5-5.6 USM lens.

Tests show nice color contrast and sharpness, and - so it's a typical sample that verifies what reviewers have said. It focuses at a decent pace but definitely not to L-native standards - but that's OK for now, and better than my no-AF adaptations of Minolta AF, Sigma SA and Pentax K lenses. Manual override is straightforward, and the S5 internal stabilization provides four stops with acceptable results (1/10s at 200mm is consistently decent, 1/8 or less would be a crapshoot). Focus is sufficiently silent if somewhat pokey, and AFc is not available at the USM grade - I'd have to check online to see if newer, higher-grade lenses can manage it. Weight isn't an issue for me, which is quite nice and sadly rare for L-mount telephoto lenses at any price. The new Sigma 20-200 and Lumix 28-200 lenses are lighter, but both stop at 200mm and are slower than this lens!

Viltrox EF-L adapter summary: 

• Viltrox EF-L (first edition, not Pro)
• adapter weight is 134 grams
• AFc is not available with USM sample lens
• camera screen shows "use AF-S" when set to AFc
• O-A switch - needs to be A with 100-300!

Canon EF 100-300 f/4.5-5.6 USM summary:

• Tests show nice color, contrast and sharpness (noted in reviews)
•  some chromatism away from center at longer focal lengths (also noted)
• manual override is straightforward - just rotate ring at base of lens
• 640 grams with adapter; weight is very nice
• no IS within, but S5 internal stabilization provides four stops
• f/4 only to about 120mm but f/5 to 180mm!

Curious bonus coverage!!

The lens does not focus accurately with my polarizing filter! It took me a dozen shots or so to remember that I'd put the filter on (a K&F nano cPL). It wasn't just shake either, as the first shots were outdoors. Focus didn't look right in the viewfinder, nor could I get a sharp image with manual focus. Once the filter was removed I felt a bunch better about what was happening. 

Still.. what's going on, we wonders?

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More news!

A poorly-focusing copy of the EF 70-210/3.5-4.5 is coming. Possibly its problem is front or back focusing on a dSLR, and it will do fine with the S5 contrast detect AF - but possibly not. In any case, I picked it up for a great price! Another experiment is also coming: a 28-300mm Tamron with VC stabilizer. This would be quite wonderful if it can work without issues, but it can be returned after a thorough exploration. It takes the same filters as the 20-60 and could be great or not-so; we shall see!

Update: the 70-210 has arrived, and it's all true. AF is fast - and wrong! It's backfocusing by a large amount, even with the supposedly more exact contrast AF of the S5. Weird! Early tests at 200mm ± show it doing well for overall IQ wide open f/5 vs the 100-300 at 5.6. I'll do some research on the back focusing; could shims help it out?