AF techies please

Started Aug 29, 2012 | Discussions thread
Alan Wolf Regular Member • Posts: 300
Re: AF techies please

I may have an overly simple understanding of it, or even totally incorrect, so please feel free to correct me. Since the lenses have their own focus motors, does the X Pro 1 essentially just send an electronic signal to the lens, which then does all the work?

This is a bit of an over simplification, and since you're curious about the general mechanism, I'll see if I can explain it a bit better. The lens and the body keep sending information back and forth until focus is achieved. You can see this in more primitive AF systems—the body would over focus the lens, and would then need to pull it back. I'm not positive, but I believe that it is still a series of steps sent by the body, acted on by the lens, and then re-acted to by the body—"focus closer", "woops, too close", "no, needs to be just a bit closer", "looks good—lets call it a lock".

So each of these operations happens really fast, but any sluggishness in the lens system (or the AF processor in the body) gets multiplied by the number of steps to achieve lock. What a firmware improvement can do is fine tune the discussion between the two, and maybe change some of the operating instruction set.

I don't have experience with the X100, but when the XP1 came out, the general opinion seemed to be that it was much better than when the X100 was new, so I'm sure Fuji did utilize as much of the relevant improvement as they could. And the most comparable lens in the X sys. to the x100 lens would be the 18, which I think is the faster of the two.

 Alan Wolf's gear list:Alan Wolf's gear list
Fujifilm X-Pro1 Fujifilm X-Pro2 Carl Zeiss Distagon T* 4/18 ZM Carl Zeiss Distagon T* 2,8/25 Carl Zeiss Planar T* 1,4/50 +21 more
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