XPro1 erratic focus?

Started Oct 11, 2012 | Discussions thread
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a l b e r t
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XPro1 erratic focus?
Oct 11, 2012

I've been using the XPro1 for a couple of months now and I found the AF performance frustrating.

It seems to be focusing on what it finds with the highest contrast instead of where I point the white box to.  I've more missed shots than all the DSLRs I've used in the past (D70, D200, D300s, D700, D3s, 20D, 30D, 40D, 400D, etc.)  I know it is no DSLR, but I certainly expect it to perform better.

So I did a couple of tests.  35mm f/1.4 lens was used.

The first one I pointed the camera out to my bedroom window during the day.  There was a dark aluminum frame in the middle of the window, which was where I point the AF white box onto.  The backdrop was some greenery on the hill.  I found the XPro1 struggling to focus on the window frame.  By looking at the distance scale, I found that it was jumping between 2m to infinity.  The actual distance was about 2m, but I saw it locking in focus most of the time from about 2-2.3m if I repeatedly engage AF.  That's like 0.3m of AF error!

The second test was AF at night by pointing focus to my 50" plasma TV while I've a TV program running.  This distance between me and the TV screen is about 4m.  The AF is even more erratic, jumping from 1.5m to infinity.  I tried to focus on faces and a variety of high contrast subjects.

I found that the XPro1 AF algorithm has trouble locking onto anything with high horizontal contrast.  If you have a horizontal split where the top part is bright and the bottom part is dark, it just cannot AF.  It has no problem with a vertical high contrast split.

Finally, please give us face detect AF.  Fuji pioneered this, and it is a very useful feature especially with a contrast detect AF system.  I found the AF so erratic that it can't even lock onto human faces accurately half of the time in moderately low light (AF illuminator was not on).  It has great trouble with dark or very light complexions, both point to a low contrast subject.  What's the use of a f/2 or f/1.4 lens if it cannot AF accurately?

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