New Olympus 17mm 1.8

Started Mar 7, 2014 | Discussions thread
Anders W Forum Pro • Posts: 21,466
Re: 17mm f1.8 is DEFINITELY faster than 20mm f1.7 as regards AF

Jeff Tokayer wrote:

Anders W wrote:

Jeff Tokayer wrote:

Anders W wrote:

I have tested the AF speed of the 20/1.7 against that of the 12/2, the 45/1.8, and the 14-45/3.5-5.6 under strictly controlled conditions on my E-M5. Result: The speed is for all practical purposes the same. See here for details.

Have you performed any similarly well-controlled test?

The best test are real world test.

Only if they are tests. What most people call tests aren't. They are just subjective impressions, and such impressions are not infrequently wrong.

When I walk around with my camera, I'm not doing a test, I'm trying to capture fleeting moments.

That's fine with me as long as you don't call it a test.

The 20 is a slow focusing lens.

Not in ordinary AF-S use.

That's the key word, ordinary. I don't ask my subjects to pose.

Neither do I. By ordinary AF-S use I mean shooting stills at ordinary focus distance (say 0.75 m to infinity).

The 12/2 and 45/1.8 are substantially faster, when it comes to grab shots.

What exactly is a "grab shot" and in what way does AF for grab shot technically differ from that of other shots?

As above, you barely get a chance to frame and shoot. The beauty of street photography.

That's included in what I call ordinary AF-S use.

The 17/1.8 crushes the 20/1.7 in AF speed.

Clearly not. The 17/1.8 is about as fast as the 12/2 and the 45/1.8 and they do not crush the 20/1.7 as you can see here:

As I said, real world test means going out and shooting. No props, no special lighting, no stop-watch. I do own all 3 lenses, and the 17 responds quicker than the other 2. If it only was as pocketable as the GR...

As I said, fine with me, but that leaves you open to all kinds of perceptual biases. You do know that perceptual biases exist, don't you, and that the only way to check how large a part they play is to compare with objective data.

When I first got the 20, there was already quite a bit of talk here about its slow AF. I too initially believed this "received" wisdom. Then I came across a test by Pekka Potka, which to my surprise showed that the 20 was about as fast as any other lens. See here:

This had me curious so I decided to do my own test and found that he was right. I have since repeated the test twice, using more precise measurements and more controlled conditions, still with the same result. I am not alone. Others have tried as well and arrived at roughly the same result as long as it is ordinary AF-S (see definition above) that we are talking about.

 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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