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Understanding X-T2 Auto Focus settings

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rogue_strawberry

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I have trouble understanding the way my camera (Fuji X-T2) AF works. There are three basic settings (single, continuous and manual - last one I understand obviously) and first two of these three have additional modes in the camera menu (from 1 to 6 presets number, with varying options for each of these). In addition to that there are face and eyes detection option. There is also a back button focus. With all of that it is really hard to understand what options should one use to shoot clear shots even in simple conditions (for example, subject being baby playing on a bench). I've a lot of shots that are clear, but not on the subject, sadly, most of them focus on background, some of them on random things in the frame.

How to wrap one's head around that? How continuous AF works, do I have to press back button focus before every shot? Or will it track my subject and do it automatically? Or would it only do that with face detection, and then I don't need to press the back button focus to get my subject face (or eyes) in focus?

I'd love if someone could clearly explain it all :)
 
Appreciate you asking the question. I’ve had an Xe2s for a little over a year. I’ve mastered most of the controls but don’t really understand how the AF-L and AE-L buttons on the camera’s rear work - and I’ve played with them. Have also read the owners manual and googled a variety of sites but haven’t found much help. The Fuji forum members are very responsive and helpful. The few times I’ve posted I’ve gotten real good info. I’m certain the more knowledgeable will weigh in.
 
Here is Fujifilm's AF information site: https://www.fujifilm-x.com/af/

Have you been using a DSLR or other mirrorless camera? Or is this your first?

My personal recommendation is to avoid back-button AF on Fuji.

For non-burst shooting, the simplest thing is to use AF-S and single-point (medium size is usually best, but use your judgment). Follow the subject with the AF point, but don't half-press the shutter. When you're ready to take a picture, just smoothly press the shutter button all the way down without stopping at half-press. The camera will then focus on what's in the AF point box, and the instant that focus is achieved, will take the picture.

Most of the complicated stuff is for dealing with burst shooting.

Face/Eye detect really expects a single face, like in a portrait shooting situation. It operates when the shutter button isn't being pressed, which means it drains the battery faster. If it finds a face, it will take over both AF and exposure -- once again, just press the shutter button all the way down without stopping at half-press. From what I can tell, most people don't find face/eye detect to be worth the hassle, but feel free to give it a try.

--
Co-founder of the open-source LightZone Project: http://lightzoneproject.org/
 
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To answer part of your question that hasn't been dealt with, back button focus is a technique that some people use to separate out focusing from actuating the shutter. It can be useful when using continuous auto focus to ensure the AF keeps tracking a subject (or, more accurately, keeps searching for targets to focus on) without any risk of triggering the shutter. It is a matter of personal taste; if you find it easy to keep the shutter button half-depressed, there is little point in setting up your camera for BBF.
 
ialarmedalien said:
To answer part of your question that hasn't been dealt with, back button focus is a technique that some people use to separate out focusing from actuating the shutter. It can be useful when using continuous auto focus to ensure the AF keeps tracking a subject (or, more accurately, keeps searching for targets to focus on) without any risk of triggering the shutter. It is a matter of personal taste; if you find it easy to keep the shutter button half-depressed, there is little point in setting up your camera for BBF.
Click to expand...
When using the back button focus, do you need to keep pressing it to maintain focus and hold it down while simultaneously pressing the shutter (as you would do when keeping the shutter half-pressed) or do you press and release to hold focus and then press the shutter when appropriate? I think it’s the former. Though that sounds clumsy. Half press shutter seems easier even with a risk of triggering the shutter early.
 
If you do decide to use BBF then you should disable shutter focus (using the shutter just to fire the shutter) Otherwise it will override the BBF.

BBF is best used with AF-C as it gives you the advantage of continuous focus whilst the button is held down or manual focus (and reframe) when the button is released.
 
Ron Bass said:
ialarmedalien said:
To answer part of your question that hasn't been dealt with, back button focus is a technique that some people use to separate out focusing from actuating the shutter. It can be useful when using continuous auto focus to ensure the AF keeps tracking a subject (or, more accurately, keeps searching for targets to focus on) without any risk of triggering the shutter. It is a matter of personal taste; if you find it easy to keep the shutter button half-depressed, there is little point in setting up your camera for BBF.
Click to expand...
When using the back button focus, do you need to keep pressing it to maintain focus and hold it down while simultaneously pressing the shutter (as you would do when keeping the shutter half-pressed) or do you press and release to hold focus and then press the shutter when appropriate? I think it’s the former. Though that sounds clumsy. Half press shutter seems easier even with a risk of triggering the shutter early.
Click to expand...
 
Exit10 said:
An advantage of back button focussing is that you get some of the features of both AF-C and AF-S with a single set up.

You get the normal advantages of continuous focus in AF-C but you can also focus and recompose by taking your finger off the back button to focus, move the camera and take the shot by pressing the shutter.
Click to expand...
Don't do this with Fujifilm!

This is the biggest single reason I discourage using BBF with Fuji. This technique can give you misfocused pictures when you try to simulate AF-S.

The problem is that the camera can choose to use contrast-detect AF rather than phase-detect AF at any time. Contrast-detect AF works by hunting. With AF-C and contrast-detect, the lens is constantly hunting, and is almost always out of focus. It's only in-focus for a brief instant, just long enough for the camera to check to see if the shutter release or AF-Lock has been activated. Then it goes back to hunting.

When you release the back-button, the lens is left focused wherever it happened to be at the moment you lifted your thumb. With phase-detect AF that's fine, because it just mean it's left where it was positioned by the previous focus cycle. But with contrast-detect AF, it can be left anywhere within the hunting range.

Unfortunately, there's is no way to prevent the camera from using contrast-detect AF, and no way to even tell whether it's using phase-detect or contrast-detect AF for a given shot. Well, unless you're using one of the slow-focusing primes and can hear the lens grinding along during hunting and can watch the focus wobble in the viewfinder.

Furthermore, when you release the back-button you disengage AF entirely. The problem with that is that the camera will happily take the picture regardless of focus status. The main additional case of interest here is when the camera did use phase-detect but failed to achieve focus. Focus Priority normally would prevent the camera from taking a picture under those conditions, but it only applies while the AF is active.

If you use BBF with AF-C, keep your thumb on the button until the shutter has been released. If you release your thumb, the lens probably will be in focus, but is that what you want?
 
ialarmedalien said:
To answer part of your question that hasn't been dealt with, back button focus is a technique that some people use to separate out focusing from actuating the shutter. It can be useful when using continuous auto focus to ensure the AF keeps tracking a subject (or, more accurately, keeps searching for targets to focus on) without any risk of triggering the shutter. It is a matter of personal taste; if you find it easy to keep the shutter button half-depressed, there is little point in setting up your camera for BBF.
Click to expand...
Oh, I know what BBF is, I've been using it exclusively since the first days I've bought the camera and it became my second nature already. My question is mainly about understanding all the AF-S, AF-C, AF presets combinations for real life usage.
 
lewiedude2 said:
Read this as it has lots of useful information. There has been an update from v3 or the firmware for my camera (x-T2) to v4.1. But, this will get you started.

https://www.theoverratedphotographe...tog/ArticlesF/Fujifilm-AF-The-unwritten-guide

Keep searching for information and watch some YouTube videos on our camera set up recommendations.

Good luck!
Click to expand...
Thanks for the link. Unfortunately, I might be reading it wrong, but it is mostly praising zone based AF (something I have admittedly, haven't been using at all) and DSLR's. The only useful thing I've found there was to use AF-S instead of AF-C in low light conditions, but that's pretty much it.
 
Doug Pardee said:
Here is Fujifilm's AF information site: https://www.fujifilm-x.com/af/

Have you been using a DSLR or other mirrorless camera? Or is this your first?

My personal recommendation is to avoid back-button AF on Fuji.

For non-burst shooting, the simplest thing is to use AF-S and single-point (medium size is usually best, but use your judgment). Follow the subject with the AF point, but don't half-press the shutter. When you're ready to take a picture, just smoothly press the shutter button all the way down without stopping at half-press. The camera will then focus on what's in the AF point box, and the instant that focus is achieved, will take the picture.

Most of the complicated stuff is for dealing with burst shooting.

Face/Eye detect really expects a single face, like in a portrait shooting situation. It operates when the shutter button isn't being pressed, which means it drains the battery faster. If it finds a face, it will take over both AF and exposure -- once again, just press the shutter button all the way down without stopping at half-press. From what I can tell, most people don't find face/eye detect to be worth the hassle, but feel free to give it a try.
Click to expand...
 
Exit10 said:
Ron Bass said:
ialarmedalien said:
To answer part of your question that hasn't been dealt with, back button focus is a technique that some people use to separate out focusing from actuating the shutter. It can be useful when using continuous auto focus to ensure the AF keeps tracking a subject (or, more accurately, keeps searching for targets to focus on) without any risk of triggering the shutter. It is a matter of personal taste; if you find it easy to keep the shutter button half-depressed, there is little point in setting up your camera for BBF.
Click to expand...
When using the back button focus, do you need to keep pressing it to maintain focus and hold it down while simultaneously pressing the shutter (as you would do when keeping the shutter half-pressed) or do you press and release to hold focus and then press the shutter when appropriate? I think it’s the former. Though that sounds clumsy. Half press shutter seems easier even with a risk of triggering the shutter early.
Click to expand...
Click to expand...
 
Doug Pardee said:
Exit10 said:
An advantage of back button focussing is that you get some of the features of both AF-C and AF-S with a single set up.

You get the normal advantages of continuous focus in AF-C but you can also focus and recompose by taking your finger off the back button to focus, move the camera and take the shot by pressing the shutter.
Click to expand...
Don't do this with Fujifilm!

This is the biggest single reason I discourage using BBF with Fuji. This technique can give you misfocused pictures when you try to simulate AF-S.

The problem is that the camera can choose to use contrast-detect AF rather than phase-detect AF at any time. Contrast-detect AF works by hunting. With AF-C and contrast-detect, the lens is constantly hunting, and is almost always out of focus. It's only in-focus for a brief instant, just long enough for the camera to check to see if the shutter release or AF-Lock has been activated. Then it goes back to hunting.

When you release the back-button, the lens is left focused wherever it happened to be at the moment you lifted your thumb. With phase-detect AF that's fine, because it just mean it's left where it was positioned by the previous focus cycle. But with contrast-detect AF, it can be left anywhere within the hunting range.

Unfortunately, there's is no way to prevent the camera from using contrast-detect AF, and no way to even tell whether it's using phase-detect or contrast-detect AF for a given shot. Well, unless you're using one of the slow-focusing primes and can hear the lens grinding along during hunting and can watch the focus wobble in the viewfinder.

Furthermore, when you release the back-button you disengage AF entirely. The problem with that is that the camera will happily take the picture regardless of focus status. The main additional case of interest here is when the camera did use phase-detect but failed to achieve focus. Focus Priority normally would prevent the camera from taking a picture under those conditions, but it only applies while the AF is active.

If you use BBF with AF-C, keep your thumb on the button until the shutter has been released. If you release your thumb, the lens probably will be in focus, but is that what you want?
Click to expand...
 
rogue_strawberry said:
rogue_strawberry said:
Now this is very useful and interesting information about AF-C and BBF. The question is, if one would instead of keeping the thumb all the time (and draining battery even faster by that) decided to use native half-pressed shutter release button focusing, then how do you even compose your pictures, if the focus point is in the middle of the frame, focusing is inherently connected with shutter release by the button and there is no chance for proper picture framing?
Click to expand...
Click to expand...
Move the focus point
 
Exit10 said:
Exit10 said:
Exit10 said:
Now this is very useful and interesting information about AF-C and BBF. The question is, if one would instead of keeping the thumb all the time (and draining battery even faster by that) decided to use native half-pressed shutter release button focusing, then how do you even compose your pictures, if the focus point is in the middle of the frame, focusing is inherently connected with shutter release by the button and there is no chance for proper picture framing?
Click to expand...
Click to expand...
Move the focus point
Click to expand...
This is obvious but also obviously unusable in any situation other than shooting a static object. Good luck with the three press and a point movement focus point changing when shooting a kid or sport event or a bird or a butterfly or moving model. Not going to happen, I'm afraid...
 
This is going to be a challenge regardless of whether or not you've assigned AF-ON to a button or to the shutter release. A quick test reveals that the focus point can't be moved with the joystick when AF-ON is on, regardless of what button you have it assigned to.
 
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