Jump to content

For those of you who don't trust the autofocus of the Fuji XT1:


abjurina

Recommended Posts

I just shot a wedding last evening in the poorest lighting situation I've ever had. The Fuji focused normally...THEN the DJ turned down the lights even further. Let's say at f1.4 1/60th at 6400 ISO I was two-stops under.

 

However, my wife was shooting her canon 6d and was having trouble with autofocus as well. As frustrating as it was, it's comforting to know that if a Fuji is going to struggle in low-light these days, it's not going to be any worse off than most other DSLRs.

Link to post
Share on other sites

One thing in the favor of mirrorless cameras is that the focus is based upon the actual image. DSLRs use phase-detect which can result in fore or back focus. My D700 has memory to fine tune the autofocus of up to 12 individual lenses. If a contrast-detect camera focuses on the wrong subject, it is user error.

Link to post
Share on other sites

MILCs can use the maximum aperture of the lens (such as 1.4 or 1.2), while DSLRs autofocus with dedicated sensors that can't make use of anything brighter than f/2.8. 

 

So with MILCs like Fuji X, it really depends on the lens you use. Use a bright lens (even if you stop down for the shot) and your low-light AF experience will improve.

Link to post
Share on other sites

Also remember that "open aperture" AF metering is only available in AF-S and MF (Instant-AF) modes. Not in AF-C mode. Instead, AF-C is always using the working aperture of the shot.

 

This is also important for daylight shooting, as stopping down in AF-C will increase your DOF, but it will at the same time decrease the chance that the camera can still use the fast predictive PDAF instead of the slower CDAF to track your subject. So stopping down can actually mean that your action series works less well (= less keepers) than shooting the same scene with a wide open lens and less DOF.

 

That's why it's important to know how your camera actually really works. Since Fuji doesn't explain any of this, I spend countless hours "reverse engineering" such details, then sharing them in forums, blogs, books and workshops that cover such "secrets". It's simple news to use.

 

It's also important to understand the effects that Face Detection can have on AF performance. I have seen many users always keeping it turned on, which is clearly a mistake.

 

Other users have problems determining proper settings for AF-S and AF-C priority: Release or Focus? It depends, but as long as you exactly know what these options are doing, you can improve your keeper rate.

 

Not to mention users that keep their camera at factory settings for parameters such as Power Management and not enabling High Performance Mode. Terrible mistake.

 

And how does/can Pre-AF influence your AF performance? Are there instances where Pre-AF is actually recommended? Well, yes, but certainly not always, so don't turn it on by default.

 

How do Single-Point AF frames actually work in firmware 4? What's the practical difference between CDAF and PDAF, what does each of these two AF methods "like" in a subject? How can we use this information to increase AF speed and accuracy by pointing the camera at patterns and objects that either the CDAF or the PDAF are particularly fond of? In my world, that's useful information, too, so we are practicing this kind of stuff in our workshops.

 

What about AF zones? Yep, they are new, but how do they actually work, and how can we use this information to increase our AF keeper rate? And what's the difference between an AF zone in AF-S and one in AF-C, anyway?

 

Or let's talk about the new WIDE/TRACKING. Pretty much useless in concert with AF-S, but very useful in concert with AF-C. At least in some scenarios, where real "3D tracking" is required.

 

The more features and options we get, the more homework we have to do. For me, it's not about trusting the autofocus. It's about knowing it. 

Link to post
Share on other sites

It's about knowing it. 

 

It's just like a car. If you try to drive from a parking lot by switching to 4th gear and cranking up the radio volume, you gonna fail: without a motor running all of these manipulations are futile. Finally you start the motor, and there's a brief weird noise from under the hood, then suddenly everything goes dark and silent. But why?…

Link to post
Share on other sites

It's just like a car. If you try to drive from a parking lot by switching to 4th gear and cranking up the radio volume, you gonna fail: without a motor running all of these manipulations are futile. Finally you start the motor, and there's a brief weird noise from under the hood, then suddenly everything goes dark and silent. But why?…

 

That's why I'm puzzled by users who change camera systems like underware. Today Fuji, tomorrow Sony, then Olympus. I envy them, because it takes me months to fully understand one (!) system: the sensor, the DR expansion scheme, the autofocus system etc. Those guys must either be geniuses, or they have no clue what they are actually doing.

 

There are so many details that are worth knowing. For example: Fuji has the LMO, and other brands now offer something similar (and yet different), but what exactly is the LMO affecting? Trust me, it's about more than just reducing diffraction, as the LMO influences at least two more factors that Fuji isn't talking about.

 

That's why I'm glad that Fuji isn't introducing 3 new sensors every year, like Sony is doing. I'd have a hard time catching up. Keeping X-Trans II for 3 years helps me, as I find more time taking pictures instead of studying how the new sensor works and behaves when pushed to or over its limits. And where are those limits, anyway? We need to know, but it takes time to find out.

 

Make no mistake: These retro cameras may look "simple", but in reality, they are sophisticated "camera simulators", almost like a flight simulator. With the exception of the zoom ring, not a single button, dial or control is hard-wired, not even the on/off switch or the aperture ring. There's plenty of high-end computer magic happening under the hood, and some of it just isn't trivial. And since Fuji doesn't reveal much useful information about all this, we have to find out for ourselves.

Link to post
Share on other sites

There are so many details that are worth knowing. For example: Fuji has the LMO, and other brands now offer something similar (and yet different), but what exactly is the LMO affecting? Trust me, it's about more than just reducing diffraction, as the LMO influences at least two more factors that Fuji isn't talking about.

 

Two more factors affected by LMO, eh? Let me guess, CA suppression and… Well, you lost me on a second one. And I still haven't done any tests to find out if LMO affects RAF in any way.

 

BTW, I think I found something that you probably haven't – speaking of "pushing the limits". Sometimes, when stacking 10+ frames together, the entire PDAF area becomes visible as a distinct noise pattern that is different from the rest of the frame. That might be important for scientific and forensic photography, maybe to the star trail stacking to some degree.

 

Here's an example (just a crop of the bottom right corner of PDAF zone):

 

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Link to post
Share on other sites

  • 1 month later...

On my last wedding I'm also has to work under a very, very low light. 

 

I wonder if we can use the Nissin i40 ( I don't have the flash yet) setting the flash off, but using the AF Focus Assist. We can keep shooting ambient light but the focus might be faster and accurate.

 

Any thoughts?

Link to post
Share on other sites

I wonder if we can use the Nissin i40 ( I don't have the flash yet) setting the flash off, but using the AF Focus Assist. We can keep shooting ambient light but the focus might be faster and accurate.

If I'm not wrong i40 AF assist doesn't work with Fuji. Also I never had an option on Nikons to have flash AF assist with no flash. Nikon has special su-800 unit for that. Nevertheless it doesn't mean there is no way to force flash AF assist work.

 

Why is on-body lamp not an option for you?

Link to post
Share on other sites

I have i40 and the auto focus assist does not work on it (using it on XT1).  The autofocus assist light on the camera body is what the camera will use if it thinks it needs it.  Problem is that little light on the camera sucks.

 

I have found since the latest firmware release on the XT1 and using phase detection ... the autofocus under poor lighting conditions at my wedding receptions have gotten much much better to do.  Particually on the dance floor when simply holding the camera up high, using ultra wide lens and just pushing the shutter release.  Much much higher percentage of keepers than before latest firmware and using the phase detection.

Link to post
Share on other sites

What surprises me the most is that some people, like the OP, report results as good as DSLRs, while others claim Fuji is still years behind concerning AF. Is that really just ignorance on the user's part...?

I would say a lot of times yes.  Although it does depend on what you are shooting, you can't force one machine to work like another.  You have to learn to use the Fuji they way it is designed to be used, and not the way a Nikon is.  I think that is where a lot of the problems come from.

 

There are many, many pros out there using nothing but Fuji, and they are not saying it isn't up to the task.  Obviously, it is exclusively what they are using, and it's what's paying their bills...

Link to post
Share on other sites

I had not so much luck with my XT10 last weekend. I used the XF23mm F1.4 on a local festival in a big tent with flashing colored light. ISO 2000 up to 6400. I had a lot of misses ( maybe 1/3 ) through the AF. The green focus box was large enough but in some instances I had to refocus 3 to 4 times before it got the focus right. Maybe the matter was the backlight situation since people most of the time where standing with the back to the lighter scene. Even if I put the sqare on the face or chest it gave me a green box but with focus on the background. Very annoying since I lost some scenes completely.

 

Another think that I can not understand is flash with Fuji cameras. You popup the flash in a dark szene push the trigger and sometimes it doesn't fire... I gave my XT10 away to another person, popped up the flash and started Auto Mode. He took 6 pictures and only 2 times the flash fired. I don't know why. And if you use flash the camera does not adjust ISO for flash. Auto-ISO is at ISO6400 or 4000 when using flash. Does I miss an option?

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...