Using Back Button Focus - For Birds and Landscapes

[Brownbear]

Back Button Focus (BBF)

I’ve finally mustered up the courage to try BBF. I’ve been testing it out for the past week to see if it works well for me, or not. I feel that I have a better understanding from my trial but I’m still not 100% clear therefore I would like to share my understanding to see if it is correct.

My primary motivation to try BBF is to see if it enables me capture more action shots in focus.

I foresee using BBF mostly for birds in flight (anything moving) but also for stationary birds to recompose for a better composition while using the center focus point for the sharpest focus. That said if I decide to switch to BBF I also need to understand how to use it for landscapes when using auto focus as switching back and forth between focusing methods depending on the scene just wouldn’t work well for me. Ie; too, many buttons to think about when composing an image.

A-EL button on my Nikon D7100 is now set to Auto-Focus On

With this new set up…

AF-C & AF-S set to Focus for Priority Selection

Single Center Point Focus/Manual Mode but using auto ISO to a max setting to suit the changing lighting conditions.

Camera Settings
For Birds in Flight OR a Stationary Bird (with the intent of capturing say lift-off or recomposing)

With my camera “release mode” dial set to Release Mode – Continuous High

1A - Bird in Flight
- When I press the AE-L button its new role is to grab focus on the bird (instead of the shutter button).
- Once I grab focus on the bird as long as I am able to hold the BBF down while keeping my focus point on the flying bird – the bird will remain in focus. When I release the shutter it enables me to capture more shots of the bird in flight but because I don’t have to refocus, I’m able to manage more in-focus shots.

1B - Stationary Bird

Recompose Scenario

I press the BBF button to grab focus on the bird. I release my hold on the BBF and recompose to place the bird somewhere else in the frame, press the shutter button and the bird is still in focus.

Question…
Is it correct to say that BBF would with the release dial set to Continuous Low, work exactly the same as I have outlined above? Simply because in this mode my camera is continually working to retain focus and it is simply a matter of low speed or high speed?

Preparing for Action Scenario

I press the BBF button to grab focus on the bird and release my press on the BBF as soon as the bird takes flight. Now when I press the shutter button the bird is still in focus.

Using BBF for a landscape image

As above but with the single focus point placed where I wish, and a set ISO. Which raises a point of confusion.. With BBF would one use the center focus point and place this on the desired focus point say 1/3 of the way into the scene, and recompose? (sharper focus with center focus point), or just use single point focus on the desired focal point?

And

AF-S with the release mode set to Single shot

I press BBF to acquire focus, hold the BBF down and press the shutter - my shot is in focus.

I press BBF to acquire focus, release the BBF button and recompose. When I press the shutter button my shot should still be in focus but this does not seem to always be the case with every shot.


I would like to finish by making a special request that the responses be kept simple and easy to understand, with no debates about the merits of BBF for different types of scenes and differing exposures – simply because at this point in time my only goal is to understand how focusing works in BBF.

I should say that I have tested BBF out in the modes presented. It seems to work well enough for me for Birds in flight and recomposing a stationary bird shot. It is the use of BBF in AF-S and Single shot mode where I’m finding that more out of focus shots.

Thank you in advance.

[Stagecoach]

Hi Christina,

One comment jumps out at me here;

I press BBF to acquire focus, release the BBF button and recompose. When I press the shutter button my shot should still be in focus but this does not seem to always be the case with every shot.

Firstly, I'm totally assuming you are not talking about an occasional problem where the action of 'physically moving' the camera has caused the target to become OOF due to a very small DOF.

Right,

From what you say it suggests that on pressing the shutter button the camera is focusing again for this to happen, but according to the manual this would not happen.

Can you undertake a simple test indoors to narrow things down;

- in this mode focus on something close, remove finger from BBF button. Re-compose with AF point over something far away. Press Shutter button -. Can you hear/see the lens re-focusing??

The above should give more info to work on.

I can simulate what could be happening very easily on my camera but on checking your manual it's immediately obvious settings are entirely different so I will not complicate things.

Dave undertook a full set of test scenarios with results in the last BBF thread and came to some conclusions.

Grahame

[Brownbear]

Hi Grahame,

Thank you for your reply.

With respect to whether I know for sure that the "out of focus shots" are not due to physically moving the camera, I don't know for sure. To recompose one needs to move the camera. I should say that recomposing an image is new to me because I usually using single point focus.

This morning I tried a few test shots using an aperture of f/8 with this mode Single shot/Single release (Test 11) while removing my finger from the BBF button after acquiring focus.

It was just after sunrise (low light) and also foggy (low contrast) but I could hear the beep to say that focus was achieved.

Scenario 1 - Wooden shack on water... Recomposed... Out of focus or maybe just blurry (hand held/very slow shutter speed simply because I was just trying it out) A couple of shots in focus, most out of focus

Scenario 2 - A heron perched on a tree over a stream... Recomposed... Most in sharp focus but not all. Hand held/better light. Again f/8. (whereas with Continuous AF at high speed, recompose, same scene all shots in focus)...

Your Exercise..


1. Focused on a fruit bowl on the dining room table, released hold on BBF button, recomposed. All shots in focus. (photos of kitchen with fruit bowl in front)

Because I was curious

2. Focused on a fruit bowl on the dining room table, kept my hold on BBF button, recomposed, pressed the shutter. All shots in focus.

Which is the better method to use 1 or 2, and why?

It does not appear to be the case that my shutter button is trying to focus.. So perhaps it is just camera movement but to recompose one has to move the camera albeit slowly and carefully... horizontally on the same plane... etc... And indeed I moved the camera while doing your exercise and all my shots are in focus, the opposite of this morning.

Yes, I have printed Dave's summary and I'm testing the modes I would use (Tests 10,11 & 12) in order to figure out how it works in a practical manner in a way that I can understand.

This test/exercise is #11.

Thank you.

[Stagecoach]

Hi Christina,

I'll have a go and my comments are based on the content of your D7100 manual

Hi Grahame,

Thank you for your reply.

With respect to whether I know for sure that the "out of focus shots" are not due to physically moving the camera, I don't know for sure. To recompose one needs to move the camera. I should say that recomposing an image is new to me because I usually using single point focus.

This morning I tried a few test shots using an aperture of f/8 with this mode Single shot/Single release (Test 11) while removing my finger from the BBF button after acquiring focus.

It was just after sunrise (low light) and also foggy (low contrast) but I could hear the beep to say that focus was achieved.

Scenario 1 - Wooden shack on water... Recomposed... Out of focus or maybe just blurry (hand held/very slow shutter speed simply because I was just trying it out) A couple of shots in focus, most out of focus

Scenario 2 - A heron perched on a tree over a stream... Recomposed... Most in sharp focus but not all. Hand held/better light. Again f/8. (whereas with Continuous AF at high speed, recompose, same scene all shots in focus)...

I will not comment on the above because there are too many 'maybes'

Your Exercise..


1. Focused on a fruit bowl on the dining room table, released hold on BBF button, recomposed. All shots in focus. (photos of kitchen with fruit bowl in front)

Because I was curious

2. Focused on a fruit bowl on the dining room table, kept my hold on BBF button, recomposed, pressed the shutter. All shots in focus.

Which is the better method to use 1 or 2, and why?

My understanding is that both methods you describe above will give you the same result when using AF-S(single) focus mode.

For 1. above, after releasing hold on BBF button focus remains locked until BBF button is pressed again.

For 2. above, keeping hold of the BBF button does nothing whilst you are in AF-S(single) focus mode. (If you had of been in AF-C the camera would have continued to focus on anything in front of your chosen AF point)

In AF-S(single) focus mode pressing the BBF button (what you have assigned the AE-L/AF-L button to do) simply causes the camera to focus at your target and lock focus at that distance however you move/frame.

From the D7100 Manual page 77;

Locking Focus with AF-ON Button
If desired, the autofocus can be assigned to a separate button in the Custom Settings menu, in which case focus will lock when the button is pressed and remain locked until the button is pressed again. The shutter can be released at any time regardless of the options selected for Custom Settings a1 (AF-C priority selection) and a2 (AF-S priority selection), and the in-focus indicator will not be displayed in the viewfinder.


I believe the above extract from the manual should explain all, (assuming the manual is correct)

What is quite clear is that the procedure and options for undertaking BBF are different between some Nikon models.

Edit - Further comment; Having read Dave's tests again and yours with carpets and fruit bowl/kitchen subjects I used a sharp edged pillar some 8ft from me with a treeline/sky at the horizon to the side of it with my camera at f/2.8. This gave very definite indication of what was happening, e.g. if the camera went off focus from the pillar it was a mega blur.

Grahame

[Bobobird]

I have been using BBF for the past 2 or so years. Will never go back be it for single or burst shots.

It is quite simple.

For BIF just hold that button down and fire the shutter when you wish for how long you wish.

For stationary acquire focus, let go the button, shoot.

For recompose, put your subject where you want in the frame. Move a focus point to the subject. Get focus, shoot. Move focus point back to where you normally have it. The trickiest part is the last bit. I often forget.

[AB26]

Christina,

Three points:
1.) Center focal point does not render sharper images than any other focal point. Cross tipe focal points make it easier to focus on low contrast subjects and in low light conditions.
2.) Differentiate between focal point and focus point. Focal point is that little block you see in the viewfinder (I think your camera has 51 of them) and focus point is the point on the subject you wish to focus on.) Set your focal point on the focus point within the chosen composition. Keep it there, for that is where the camera will focus.
3.) Keep your eye on the green light in the viewfinder. See how it responds when you press and release buttons in different combinations and find a way of keeping that light on, until you know better.

[Brownbear]

Hi Christina,

For 2. above, keeping hold of the BBF button does nothing whilst you are in AF-S(single) focus mode.
Grahame

Hi Grahame,

Thank you for taking the time. Truly helpful. It sounds like my out of focus shots using Single Shot release and AF-S were likely due to challenging focus conditions/camera movement and mistakes on my part.

I will try this again on a bright sunny day, perhaps with a pole and treeline as in your example. I will do so until I'm certain of it's use. I'm still confused about #2 as the shots I took last night seem to be in focus (as seen through the viewfinder) which to me indicates two ways to use the single shot method.

Thank you.

[Brownbear]

Hi Bobo,

Thank you for sharing. Indeed it is very nice to know that you use BBF. With respect to birds in flight I do feel like I am able to capture more in between moments.

And also thank you for the simple explanation of how you use BBF in the field in various scenes.

I have been using BBF for the past 2 or so years. Will never go back be it for single or burst shots.

It is quite simple.

For BIF just hold that button down and fire the shutter when you wish for how long you wish.

For stationary acquire focus, let go the button, shoot.

For recompose, put your subject where you want in the frame. Move a focus point to the subject. Get focus, shoot. Move focus point back to where you normally have it. The trickiest part is the last bit. I often forget.

[Brownbear]

Hi Andre,

Thank you for the helpful points, correction of my terminology and tips. All noted.

#3... Great reminder! I will do just that. Thank you.

Christina,

Three points:
1.) Center focal point does not render sharper images than any other focal point. Cross tipe focal points make it easier to focus on low contrast subjects and in low light conditions.
2.) Differentiate between focal point and focus point. Focal point is that little block you see in the viewfinder (I think your camera has 51 of them) and focus point is the point on the subject you wish to focus on.) Set your focal point on the focus point within the chosen composition. Keep it there, for that is where the camera will focus.
3.) Keep your eye on the green light in the viewfinder. See how it responds when you press and release buttons in different combinations and find a way of keeping that light on, until you know better.

[Clactonian]

I think the key thing is to operate the BB focus system in the manner that best suits you within the control capabilities of your camera.
I have several different DSLRs (I keep my old models) and use BBF on each of them despite them all having slightly different controls, but I have evolved a method that works on each so that I don't need to think about which camera I'm using.
In simplistic terms I use centre point focussing and recompose whilst keeping my thumb pressed on the back focus button throughout the shot taking process, be that in single shot or continuous mode. It works for me, as I say, but may not suit everybody.

[Stagecoach]

Hi again Christina,

Progress I think........

It appears from your post No 7 that you are still unsure of the reasoning behind my statement below............

For 2. above, keeping hold of the BBF button does nothing whilst you are in AF-S(single) focus mode

As you make this comment..................

Hi Grahame,

I'm still confused about #2 as the shots I took last night seem to be in focus (as seen through the viewfinder) which to me indicates two ways to use the single shot method.

Thank you.

Yes, there are two ways to use this method in AF-S focus mode. You can remove your finger from the BBF button OR leave it on with the button pressed, each will give the same result with your D7100.

This is what I described in post 4 although perhaps it could have been worded "" keeping hold (pressed) of the BBF button does nothing ADDITIONAL to what it has already done when you initially pressed it whilst you are in AF-S(single) focus mode.""


Grahame

[Brownbear]

Thank you Mike. Truly appreciated.

I went out this morning and tried the Single Shot BBF method again while photographing a landscape and it seems to work best for me when I keep the BBF button pressed down while I recompose. Why I'm not sure but at least I've learned that, and I could manage several shots in focus.

I think the key thing is to operate the BB focus system in the manner that best suits you within the control capabilities of your camera.
I have several different DSLRs (I keep my old models) and use BBF on each of them despite them all having slightly different controls, but I have evolved a method that works on each so that I don't need to think about which camera I'm using.
In simplistic terms I use centre point focussing and recompose whilst keeping my thumb pressed on the back focus button throughout the shot taking process, be that in single shot or continuous mode. It works for me, as I say, but may not suit everybody.

[Mike Buckley]

there are two ways to use this method in AF-S focus mode. You can remove your finger from the BBF button OR leave it on with the button pressed, each will give the same result with your D7100.

I went out this morning and tried the Single Shot BBF method again while photographing a landscape and it seems to work best for me when I keep the BBF button pressed down while I recompose.

Those two seemingly contradictory statements need to be flushed out to eventually arrive at actionable information.

[Brownbear]

Hi Grahame,

Yes, we are making progress Thank you for your help.

I can see that when I am in continuous focus mode (high speed release) that when keep the BBF pressed that my camera works to keep focus on a moving subject, and that in this mode when I release my hold on the BBF button it is as though my camera switches to manual focus and holds the focus while I recompose... I can repeat this consistently with birds.

Heron... Center Point focus point and recomposed (as above)



Three Shots combined (all using the above method) (and I have 15 of him in focus )



I headed out this morning and tried Test 11 (Dave's post - Release Mode - S and AF-S)... Clear sunny morning, no mist or fog, and using a tripod.

Although I was not able to manage all the shots in focus, the majority were in focus when I kept my hold on the BBF button while recomposing. However I did have motion blur in a few images so I suspect that it is my technique while recomposing that needs work and/or it may be that when I release my hold on the BBF button something goes wonky.

Thank you for confirming that focus should be achieved whether I keep my finger on the BBF or not. This is helpful to know. I just wish it worked the same as when in continuous High Speed focus with AF-C.

Aside...
In the AF-S mode if I release my hold on the BBF button because manual focus is needed (mist/fog) is it true that I can just turn the focusing ring on my lens without setting my lens and my camera to manual focus, without damaging my camera?

Hi again Christina,

Progress I think........

It appears from your post No 7 that you are still unsure of the reasoning behind my statement below............



As you make this comment..................



Yes, there are two ways to use this method in AF-S focus mode. You can remove your finger from the BBF button OR leave it on with the button pressed, each will give the same result with your D7100.

This is what I described in post 4 although perhaps it could have been worded "" keeping hold (pressed) of the BBF button does nothing ADDITIONAL to what it has already done when you initially pressed it whilst you are in AF-S(single) focus mode.""


Grahame

[Brownbear]

Hi Mike,

I intend to head out tomorrow morning or the next morning to photograph a mountain scene at sunrise. I will try to be methodical about the process...

ie; I will photograph the scene with single shot release/AF-C while holding down the BBF while recomposing when the light is nice, and afterwards I will try a bunch of shots recomposing after releasing my hold on the BBF. I suspect it is my technique when recomposing and/or just focusing properly on landscapes because I was able to manage shots of the kitchen in focus (Grahame's exercise) with both methods.

Thank you.

Those two seemingly contradictory statements need to be flushed out to eventually arrive at actionable information.

[Stagecoach]

Those two seemingly contradictory statements need to be flushed out to eventually arrive at actionable information.

Fully agree Mike, and this must be done with SPECIFIC respect to Christina's D7100, it's Manual, her specific findings and not on assumptions.

Moving forward;

a) For Christina's tests using fruit bowl, AF-S, BBF held on OR released after achieving focus were bot reported as giving the required result.

b) From D7100 Manual page 77, Quote

Locking Focus with AF-ON Button
If desired, the autofocus can be assigned to a separate button in the Custom Settings menu, in which case focus will lock when the button is pressed and remain locked until the button is pressed again. The shutter can be released at any time regardless of the options selected for Custom Settings a1 (AF-C priority selection) and a2 (AF-S priority selection), and the in-focus indicator will not be displayed in the viewfinder.

The statement clearly suggests to me that to allow you to press it again you have to remove your finger BUT it will remain as is until you press it again.

c) From feedback from Christina I am concerned/interested that the term 'seems' is often used suggesting inconsistency or uncertainty. For this very basic operation it should either work or not work, I would expect there to be no middle ground.

There is of course the possibility of the focus and recompose that could change subject to sensor distances (trigonometry) but we are talking landscapes here.

I'm sure we will get there.

Grahame

[Stagecoach]

Hi Christina,

I have to go out but will read your reply (one with the great bird shots) in detail later. It seems we simply have one very basic operation to confirm exactly what is happening in that specific mode with YOUR camera.

Grahame

[Mike Buckley]

this must be done with SPECIFIC respect to Christina's D7100, it's Manual, her specific findings and not on assumptions.

Exactly.

[ajohnw]

I've mostly read all of the posts Christina but there doesn't seem to be a basic fact mentioned. Taken from a video on how and why to use BBF on a Nikon.

The camera is always in continuous focus and the back button simply allows it to run. So if needing single af with recomposition put a focus square where you want it and press the BB. Release and then frame.

For situations where you want continuous AF keep the BB pressed even when you take the shot.

The video showed it being used while taking a shot of a lion. The main point being that it might move so it was possible to use it single af fashion but but by keeping the BB pressed focus should be maintained if it did move.

Actually I took a lot of shots like this recently in situations where I would normally just frame and shoot and found having to press the BB on every shot a pain that also slowed things down. So I will be setting things back to the BB simply locking focus. I also have a 1/2 shutter button press locking exposure. I feel this is a good option on cameras where it's possible to see over exposure in particular immediately the shot is taken as it's possible to meter again with more sky in, half press and take the shot again.

If I need continuous I normally simply select it. It doesn't exactly take much time. I do feel though that it may be worth adding the BBF as a separate user mode. In my view BBF is of most use when selecting continuous AF is something of a pain. It's not really a panacea at all. In fact this cropped up in another thread a while ago - I went through the options and it turned out that the poster hadn't really taken the time to see just how their camera could be programmed. BBF seemed to be their only option.

One thing I have meant to try is to see what focus lock does in continuous AF. It should lock it. if the option is still available. If so that in real terms is a simpler option - always shoot in continuous and lock if needed.

I feel that using the BB for exposure lock is a bit of a waste unless some one is using spot metering or similar.

John
-

[Mike Buckley]

John,

I don't know if you are aware that we established in another thread that the BBF does not work the same on a Nikon D7000 and a D7100, much less all Nikon cameras. Personally, I wouldn't pay any attention, as Grahame mentions, to anything that doesn't explicitly reference Christina's camera, which is a Nikon D7100.