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

Started 4 months ago | Discussions thread
micksh6
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Re: 17/1.8 is significantly faster than the 45/1.8
In reply to Anders W, 3 months ago

Anders W wrote:

NZ Scott wrote:

Anders W wrote:

"Are you claiming that the 17/1.8 is noticeably faster than other modern lenses with similar AF design like the 12/2 and the 45/1.8 included in my test? If so, on what basis do you make that claim?"

Nobody seems to have answered this.

In my experience, the 17/1.8 autofocuses significantly faster than the 45/1.8 under real-world shooting conditions.

I've taken around 5000 photos with the 45/1.8 and 10,000 with the 17/1.8, often switching between the two lenses several times a day.

The difference is especially noticeable in situations that require big changes in focusing distance (ie. from near to far or from far to near) - e.g., when shooting street.

The 45 is occasionally slow enough to miss shots.

See my previous reply to your and Hen3ry's discussion about this earlier on:

http://www.dpreview.com/forums/post/53591384

In short: What you see is what would normally be expected in view of the different FLs and the way you are likely to use them since the focus lens group of the 45 usually has to move more than that of the 17 or 12 (which you noted were both faster in your experience). If you keep the amount of travel the focus lens group has to do constant (as I did in my testing with the 12 and 45), you are likely to see the difference disappear.

That doesn't explain why both 45mm F1.8 and 25mm F1.4 generally focus faster than 20mm F1.7, does it?

This test was conducted when magnifications for two different targets were the same for different FLs. According to your logic lens focusing elements would have to travel the same distance. Still, the results are different for different lenses.

There is something with Oly 45mm that makes its focusing element travel longer when refocusing to closer target under some conditions. In most other cases Oly 45mm is really fast, although 17mm F1.8 is faster.
Without knowing more details a correct answer would be - it all depends on lens design.

And answering your earlier question - why I didn't measure AF time when refocusing at the same target - because this rarely should be done in real life. I can lock focus if I need to.

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