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

Started Mar 19, 2014 | Questions thread
Anders W Forum Pro • Posts: 21,468
Re: Thank all, next question then Re: Is the Panny 20mm f/1.7 slow to focus on the GX7?

rhlpetrus wrote:

jhinkey wrote:

My experience with the new 20/1.7 on my GX7 mirrors that of Anders - if it's focusing on something not near it's pretty quick. It takes about a second to rack all the way from MFD to infinity which can seem like forever if you are in a hurry. Small AF changes at far distances are pretty fast - fast enough at least.

Also, it seems to me that the size of the AF point box seems to affect it as well - i.e., the smaller the size of the AF box the slower it is and is somewhat less reliable, but it may just be me.

Thanks all. Now my question then is: do other fast primes work similarly or are newer ones better in that respect. Af speed is my main issue with non-dslrs, I want to corner that wrt m43 before I move into the system.

As Ken Strain already mentioned, the 17/2.8 and the 20/1.7 (the first two primes for MFT) have external rather than internal focus, which makes the max speed of the lens AF mechanism lower than that of other lenses. But whether this has any implications for AF speed depends entirely on whether it's the lens AF mechanism or body processing that is the bottleneck.

For my use case (see my reply to Ken Strain above for description), it's body processing so I am just as fine AF-ing with my 20 as with any other MFT lens. This is true even if I use the smallest AF box available on my E-M5 or my old G1 and I have not noticed any reliability problems either. AF is faster with the E-M5 than with the G1 since body processing is faster with the E-M5. That's all.

In terms of sharpness, the 20/1.7 is as good as it gets, and it's nicely small and light. So if your use case resembles mine and if you don't have any reservations about the focal length (I don't since I prefer my standard prime to be slightly on the wide side, i.e., 35 or 40 mm EFL), I don't think you should hesitate to get the 20/1.7 in a kit with the GX7.

 Anders W's gear list:Anders W's gear list
Panasonic Lumix DMC-G1 Olympus OM-D E-M5 Olympus E-M1 Panasonic Lumix G Vario 14-45mm F3.5-5.6 ASPH OIS Panasonic Lumix G Vario 7-14mm F4 ASPH +28 more
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