I feel misled: Panasonic 20mm f1.7 II AF is SO SLOW!

Started 5 months ago | Discussions thread
Anders W
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Re: I feel misled: Panasonic 20mm f1.7 II AF is SO SLOW!
In reply to Mark Chan, 5 months ago

Mark Chan wrote:

Anders W wrote:

Wesley Byrne wrote:

Wesley Byrne wrote:

UPS just delivered my Panasonic 20mm f1.7 II. I had read the reviews and knew the Panasonic 20mm f1.7 autofocus wasn't fast, but I wasn't expecting it to be so unbearably slow. Some here have said that the 20mm f1.7 isn't that slow, and that it autofocuses about as fast as other m43 lenses when large focus adjustments are not needed, but they are wrong. This lens is useless for even slow moving subjects. I am definitely returning this lens.

I know the 20mm f1.7 has many fans, presumably folks who photograph static scenes. In my opinion, compared to the 17mm f1.8 and the 25mm f1.8, the 20mm f1.7 is a dog. Panasonic should be embarrassed for releasing this lens with barely-functional AF.

</end rant>

Slow AF on the 20/1.7? Absolutely. Except if you use it in ordinary AF-S in the range from 0.75 m to infinity and manage not to send it hunting. Fortunately, that exception accounts for more than 99 percent of my usage.

This is the kind of bad advice I was referring to.

It is neither advice nor bad. It is a correct observation based on controlled testing. See here:

http://www.dpreview.com/forums/post/50877416

What controlled testing did you perform?

Even in these conditions I found the 20mm f1.7 unbearably slow.

Wow Anders, at it again?

It seems I am not alone in being at it again.

When someone 'asks' if 17mm AF is faster than 20mm, what should be the simple and clearest answer?

Yes or NO. Call a spade a spade.

Not 'comparable'; not 'for ordinary use its much the same'; not for 'all practical purposes'.

Just a simple, it is. We can add 'but then I have been able to adapt my photography such that its not an issue.'

So what is wrong with the answer I gave the OP, already present in the quoted text of mine above:

"Slow AF on the 20/1.7? Absolutely. Except if you use it in ordinary AF-S in the range from 0.75 m to infinity and manage not to send it hunting. Fortunately, that exception accounts for more than 99 percent of my usage."

http://www.dpreview.com/forums/post/53579948

This way, you are not misinforming people into thinking that the 20mm lens can do what it cant. A newbie into photography would think that he had a bargain for the 20mm and only later realized the lens was not 'quick enough' for his needs; because somehow, for his 'practical purposes', he would find it slow.

In the earlier thread in which you and I discussed this, you mentioned two examples of when the AF of the 20 would be too slow for your needs. The first is when you are shooting a landscape and then suddenly discover that your kid is running toward you and turn to capture him/her "at close quarters". The second is when you try to shoot by-passing bikers.

With regard to the first example, you already got my reply in the earlier thread:

http://www.dpreview.com/forums/post/53300367

As to the second, I made a little test today specifically for you. This crop from an image of two students returning from today's picnic in the park was the result of my first try. I was standing as close to the biking path as I possibly could without blocking the traffic and, as you can see, shot wide open at f/1.7, AF-ing at the last moment.

Of course, this is not what I would normally do since it is not the most efficient approach. Rather, I would either pre-AF or MF on the place where the bikers will appear and I want to capture them and then shoot a single frame or a high-speed burst when they are at/close to the proper spot (thereby minimizing shutter lag and maximizing the chances of getting the shot the way I want it). But just in case I suddenly happen to spot an irresistible biker, it's good to know that it is possible to get the shot even without proper preparation.

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