Is the Panny 20mm f/1.7 slow to focus on the GX7?

Started Mar 19, 2014 | Questions thread
Anders W Forum Pro • Posts: 21,466
Re: Is the Panny 20mm f/1.7 slow to focus on the GX7?

traveler_101 wrote:

Just to add--

The 20/1.7 is a legendary lens for m43: when it came out it in 2009 d-preview really sat up and took notice of a lens that seemed to manifest the potential of the small camera; the reviewers called it "the first must-have lens for Micro Four Thirds." It really put m43 on the map. When I bought my E-P1 in early 2010 I ordered the 20/1.7 immediately and it has been far and away my most used lens on this system. And of course, there is much to be said for pancake lenses in a system that emphasises potability.

It's important to remember the history of the lens and to acknowledge its very high image quality (check out DOX Mark data if you have any doubts). But it is an "older" technology (already). I realise that to speak of five years ago as "older" is absurd, but that reflects just how quickly things have been developing for m43. The 20/1.7's design for focusing which relies on moving the body of the lens is a little "clunky" and it just appears/sounds/performs a bit "old fashioned" in comparison to the internally focusing MSC lenses from Olympus. As one member of this forum said, the 20/1.7 has a tendency to "hunt like a dog" (lol) and he gave a link to the following video as evidence:

And that evidence is worth absolutely nothing as shown by the discussion in the thread where it was originally posted. Of course, if you don't keep the AF target perfectly constant, you can very easily "show" one lens to hunt more than another. If you do keep it constant, as I have in my tests of hunting propensity, you will find that the 20 starts hunting at a similarly low light level as other lenses with a similar max aperture. This is of course in line with expectations since the "decision" of whether to hunt or not is made by the body on the basis of AF signal strength, and the 20/1.7 has good contrast and a wide max aperture.

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