What Is It With Fuji X and AF Performance?

Started Jan 2, 2013 | Discussions thread
57even Forum Pro • Posts: 11,339
Re: Glass half empty?

Charlesn wrote:

First, thanks to those who took the time to post thoughtful replies. I didn't open this as a troll thread to trash Fuji AF, it's just an honest question from someone who bought the X100 when it first arrived, and who recently bought the XE-1. I love what Fuji gets right, which seems to be the harder stuff, so I can't quite figure why they haven't done a better job in this area. Some of the suggestions made in this thread however do shed some light on the issue. As for comments below...

It is Fuji's first ever interchangeable lens AF camera. It is WAY ahead of any of the first generation MFT cameras and NEX's, and really no worse than some current model/lens combos.

There were (and continue to be) AF issues with the X100, which is notthe XPro-1 and now the XE-1

X100 is not an interchangeable lens camera. It does not have a lens mount.

It is a lot better than an EOS M. Or a Sigma DP2, RX1 or G1X.

Both the EM5 and G1X smoke Fuji's AF. Oly and Panny are the class leaders in CDAF. I've demo'd but haven't really shot with the RX1, but reviews seem to describe AF issues that sound pretty much on par with Fuji X, so this may be more of a draw between them.

Nope, Canon G1X really isn't that fast (I didn't say Panny GX1).

It's not as good as an EM5. However most MFT lenses are slower and the sensor is smaller, so it has more DOF hence does not need to be as accurate. The lenses are quite a bit smaller as well.

There are now many very fast MFT lenses on the market. But agreed that the greater DOF can allow for greater latitude in the accuracy of the AF.

More to the point, it can reach the "acceptable contrast" threshold with a lot fewer steps.

I also have a few screw drive lenses on my D700 which don't focus any faster (old Sigma 105 macro for instance, or the 85 F1.4 (in fact AF-D version is faster than AF-S).

I had the first generation Canon 85 f1.2L which, due to the huge size of its front element was no speed demon in focusing. But it wasn't THAT slow, and it never failed to lock focus. I find the issue with Fuji is not "slow" AF, per se, it's the inability to lock focus in moderate-low light that makes it slow, frustrating and sometimes impossible to use--the shot is gone by the time the camera focuses.

Different issue from slow focusing though. In low light they have trouble finding enough contrast, but that's a slightly different issue and somewhat under your control. I can usually find something to focus on, or simply switch to manual. I am not finding this much of an issue.

Moreover focus accuracy on the X series is much better than any SLR, in all types of light. Change the light sources (or even just the aperture with fast primes) and PDAF systems will back or front focus like a goon-un.

I understand that you're talking accuracy and not speed, but I have not found this to be true at all.

CDAF systems are measuring focus at the sensor. Generally when they get a lock its dead on (within the DOF limit anyway) provided you shoot an object with enough contrast. Yes, they can be fooled, but not that often. Moreover, manual focus check on the EVF is always accurate (not always true for SLRs).

SLRs are not really very good at AF. D7000's, 5Dmk2s and many other cameras had AF that I would class as barely adequate. My D700 would back focus under tungsten (as do most SLRs) and on some fast lenses would focus shift noticeably. Perhaps your just never noticed?

So I don't accept it's bad, and it's far from unusable. And all things considered it's actually pretty good for a first attempt, and the PDAF system coming in future cameras will make it better still.

But like I said, it's actually NOT that uncompetitive overall.

It's significantly behind competing CDAF from Oly and Panny.

Which is now third - or is it fourth generation? Like I said, MFT is easier to work with. However don't really find most NEX cameras that much better, and the new Canon is worse IMO.

But it's not like noone has brought this issue up before, so if it's a big deal why buy one? EM5 is a decent camera, so I don't really understand why people knowingly buy something with an issue that bothers them and then post about it.

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