Focus tracking with Lock-On settings

[thelordofthelight]

Hello all,

My first post here

I just have this doubt on how the setting "Focus tracking with Lock-On" (a3 on my D850) behaves.

What i have noticed is that while tracking BIF, particularly when the background has some clutter, setting the blocked shot response to 5 (Delayed) and subject motion to "Default" seems to help a lot. In its default setting of 3 or lesser value, the camera picks the background frequently.

My understanding of this setting so far (and also most of the examples out there) is that when a subject moves sideways and there is a sudden obstruction like a tree etc. the camera does not immediately attempt to focus on a new target but rather maintains the focus on the same focal plane the subject is in - This makes perfect sense when the subject moves side ways.

Now, my question is what is the ideal setting for a bird moving towards the camera in a clean background - As the focal plane shifts quickly when a subject approaches the camera, is it advisable to use Blocked shot AF response of "1" and subject motion "Erratic"?.

I just want to know if using blocked shot AF response towards "Delayed" and subject motion "Steady" would slow down the AF for approaching subjects where the focal plane shifts quickly.

Thanks!

 

[Steve]

If the camera is picking up with background frequently at a setting of 2 or 3, its likely that your AF point is falling off-target for a bit too long. If your off target too long, the camera will try to refocus. So, when you set it to 4 or 5, that's giving you enough time to get back on target - and honestly, that's what the setting is there for, so no worries .

As for a subject coming at the camera, it doesn't apply. The delay only applies to sudden changes in distance, so it won't (shouldn't) matter how its set for a subject coming at the camera if you stay on target.

The subject motion setting is more for how the subject starts and stops. If you have sudden stops and starts (like a bird bursting off a branch or landing quickly - but not slower take-offs and landings), then erratic is a good choice. For normal flight shots, in the middle or steady is usually fine.

 

[Warren D]

By the same token, if lock on is set to 4 or 5, if AF does drift off to the BG, wouldn't it take longer to get AF back on the subject?

 

[Steve]

By the same token, if lock on is set to 4 or 5, if AF does drift off to the BG, wouldn't it take longer to get AF back on the subject?

Yes - but only if you keep AF engaged. If you release AF and put the AF area back on the bird, it'll lock back on. Although, which is faster is up for debate. Lately, I've been using longer delays and just releasing AF as needed. However, I think at certain settings (like 2 or 3) it's probably actually faster to keep AF engaged and stay on target until the camera refocuses (it's less than a half second) than to completely disengage and reengage AF.

 

[Steve]

Too add to the post above - it also depends on the subject too and my ability to stay on target. The A3 setting is not a set-it-and-forget-it adjustment.

 

[Warren D]

Yes - but only if you keep AF engaged. If you release AF and put the AF area back on the bird, it'll lock back on. Although, which is faster is up for debate. Lately, I've been using longer delays and just releasing AF as needed. However, I think at certain settings (like 2 or 3) it's probably actually faster to keep AF engaged and stay on target until the camera refocuses (it's less than a half second) than to completely disengage and reengage AF.

I seem to notice that if I try to re-engage, the AF almost seems suck to the BG. I've got the shutter set for single point af with group AF on the BBAF. I'm wondering if the BBAF actual doesn't over-ride the shutter AF? Seems like it should but pumping the BBAF in situations where the AF point has slipped to the BG doesn't seem to have any effect.

 

[Ralph]

Still working on it but I found that for me 2 was a better number if I drifted off target and I am still holding the focus button down. Seem to be getting more keepers. When I was on 3 it seemed a little sticky as Steve would say. But like I said, I’m still experimenting.

 

[Steve]

I seem to notice that if I try to re-engage, the AF almost seems suck to the BG. I've got the shutter set for single point af with group AF on the BBAF. I'm wondering if the BBAF actual doesn't over-ride the shutter AF? Seems like it should but pumping the BBAF in situations where the AF point has slipped to the BG doesn't seem to have any effect.

How exactly are you set? You're using shutter release AF, AF mode set to single, then the back button is set to Grp - but is it just Grp or Grp + AF-On?

 

[thelordofthelight]

I use blocked shot response set to 5 and subject motion set to default when the background is cluttered and it works very well on my D850. Whenever the AF locks on to the BG, obviously due to user errors, i just release the AF-ON and press it again to refocus on the subject.

The reason i had this doubt is because the camera knows it must immediately refocus at a setting of 1 or 2 vs wait for a second before refocusing when set to 4 or 5 based on the changes in the plane of focus (depth). I am not sure if the cameras are intelligent enough to know that the obstruction was actually a different subject or object than the one that the camera is currently tracking.

Now, if one thinks of the same logic (tracking based on depth), for an approaching subject the camera must adjust its focus much quicker as the focal plane changes in real time vs a side ways movement where the focal plane is relatively the same. This is why i was wondering if using a setting of 1 and erratic will make the AF more responsive and help get more keepers in a burst vs having those slightly out of focus shots in a burst (again, for subjects that are approaching the camera and not the ones moving in parallel).

 

[Warren D]

How exactly are you set? You're using shutter release AF, AF mode set to single, then the back button is set to Grp - but is it just Grp or Grp + AF-On?

I'll have to check, that might be the problem. Nope, it's Grp+AF ON

 

[Steve]

I use blocked shot response set to 5 and subject motion set to default when the background is cluttered and it works very well on my D850. Whenever the AF locks on to the BG, obviously due to user errors, i just release the AF-ON and press it again to refocus on the subject.

The reason i had this doubt is because the camera knows it must immediately refocus at a setting of 1 or 2 vs wait for a second before refocusing when set to 4 or 5 based on the changes in the plane of focus (depth). I am not sure if the cameras are intelligent enough to know that the obstruction was actually a different subject or object than the one that the camera is currently tracking.

Now, if one thinks of the same logic (tracking based on depth), for an approaching subject the camera must adjust its focus much quicker as the focal plane changes in real time vs a side ways movement where the focal plane is relatively the same. This is why i was wondering if using a setting of 1 and erratic will make the AF more responsive and help get more keepers in a burst vs having those slightly out of focus shots in a burst (again, for subjects that are approaching the camera and not the ones moving in parallel).

I follow the thought process, but keep in mind that the only time the delay "timer" is only started is if there is a drastic change in distance - something that's VERY easy for the PDAF system to determine. If what's under the AF point is in phase and a split second later it's grossly out of phase, the timer starts. That shouldn't be the case with a bird flying towards you since the motion is steady. The bird isn't at 20 feet and then at 15 feet a microsecond later. Instead, it's at 20, 19, 18 etc. Of course, if the AF point wanders off, then the camera sees the a significant phase difference and the timer starts.

 

[Woodpecker]

I follow the thought process, but keep in mind that the only time the delay "timer" is only started is if there is a drastic change in distance - something that's VERY easy for the PDAF system to determine. If what's under the AF point is in phase and a split second later it's grossly out of phase, the timer starts. That shouldn't be the case with a bird flying towards you since the motion is steady. The bird isn't at 20 feet and then at 15 feet a microsecond later. Instead, it's at 20, 19, 18 etc. Of course, if the AF point wanders off, then the camera sees the a significant phase difference and the timer starts.

After running into @Steve 's input to this topic some time ago, I tried it out and decided to put the Lock-On setting in "My menu" because I thougt I would have to change it a lot. But after a while I found out that with a bit of practice I am better off having the lock-on short or even off and give my thumb and the AF-On button a bit more work to do.

 

[pochito]

I'm a newbie with long lenses. And else. This said:
I tried my new 600mm lens hand held on some static birds. I was using 21 focus points, BBAF and the Focus Tracking setting was at 4.
I locked on a bird and started continuous firing at high speed on my D810. I used manual exposure 1/2500 f/6.3 with Auto ISO.
The distance was about 150m. The foregound and background is water.
Now: I have some difficulty holding the camera still. There is some movement while shooting. I take care not letting the back button go.
I get the locked AF point at different places in the different images, I suppose because of my trembling hand
My question.
Is it better to set the FT Lock On setting high, in order that the camera doesn't refocus at each vibration from my hand?
Or does a fast refocusing come back to the bird more immediately?
I'm confused about how the camera "thinks" :-(

 

[Steve]

Is it better to set the FT Lock On setting high, in order that the camera doesn't refocus at each vibration from my hand?
Or does a fast refocusing come back to the bird more immediately?
I'm confused about how the camera "thinks" :-(

It actually seems like you have the idea

The camera will resist letting go of the bird longer if you have it set longer, so if you allow the AF area to wander off, you have more time to get back. BUT if you do lose focus, you can move the AF area on back the bird, leave AF engaged the whole time, and it will snap back faster.

Once technique that some use is when tracking a bird coming in from a long distance to do it in "spurts". Focus on the bird, let off AF, as the bird gets closer, do it again and again until its within range - then keep the lock. I personally just focus on the bird the entire time, but some find that the on and off method works better for them.

 

[gordon_g]

The higher the number the long it take for Focus tracking to refocus.. the smaller the number the faster it ties to refocus... HOWEVER.. it's looking for a big difference in Focal plane... This setting should make ZREO difference in this case unless your focus point comes off the bird and onto the background (for instance). it's really meant to be used for Bird's in Flight... your following a bird it flies behind a tree... setting at 1 the focus will lock onto the tree... setting 5 it going to keep the focus on the bird so hopefully when he comes out from behind it he is still in Focus.

 

[Woodpecker]

Actually the answers of @Steve and @gordon_g dropped in while I started writing. SO ,that's it so far.

Once technique that some use is when tracking a bird coming in from a long distance to do it in "spurts". Focus on the bird, let off AF, as the bird gets closer, do it again and again until its within range - then keep the lock. I personally just focus on the bird the entire time, but some find that the on and off method works better for them.

I think @Steve 's suggestion is great and just by reading it I discovered that I am doing something similar. The reason is that if I shoot in difficult conditions where it not so easy to follow the bird, I sometimes loose it out of sight for a short moment. If I keep the thumb on AF-On the lens might start "hunting" for the bird so if I try to find it back I might not see it although I am looking straight at it, because the focus has just moved way out. If I release the button when loosing the bird I can find it back easier, because I can see it even if it looks like a shot with a spray can, because it has flown out of focus. But then I can activate AF again to get confirmation that is it my bird and fire.

 

[pochito]

Thanks everybody. This is helpful
I'll try it myself when it stops raining. Hehe

 

[OohMatron]

Don't forget that the amount of movement within the lens necessary to maintain focus increases almost exponentially as the subject flies towards the camera. Predictive Tracking therefore can be slowed as it nears you.

 

[Gary Shackelford]

Here's a situation where I have not had good luck retaining focus, and I don't know why:

A bird is perched and getting ready to fly. I want to keep the camera fixed and immobile on a tripod and let the bird fly across the frame using a large number of focus points while tracking focus — dynamic 153 setting on my D500 or D850. While the bird is still perched, I position it on the side of the frame to allow it to fly across the frame after takeoff. I press to begin focus (back button focus) when the bird is getting ready to fly, and I continue to press AF-On throughout the sequence until the bird has flown out of the frame. (I don't use 3D focus because I have not had good luck with it when photographing fast-moving or jerky-jerky subjects.) My typical a3 Focus tracking with lock-on settings in this scenario are Blocked shot AF response 3, Subject motion midway between Erratic and Steady. The bird flies parallel to the sensor plane, and I have a clear, unimpeded view of the bird across the entire frame. I have read the relevant section of Steve's autofocus book many times, and it seems that my settings and technique are correct and that the camera should retain correct autofocus throughout the sequence, but typically only the frames with the bird still perched and maybe a couple of frames right after takeoff are acceptably sharp; the rest are unsharp. What am I doing wrong?

 

[DRwyoming]

Here's a situation where I have not had good luck retaining focus, and I don't know why:

A bird is perched and getting ready to fly. I want to keep the camera fixed and immobile on a tripod and let the bird fly across the frame using a large number of focus points — dynamic 153 setting on my D500 or D850. While the bird is still perched, I position it on the side of the frame to allow it to fly across the frame after takeoff. I press to begin focus (back button focus) when the bird is getting ready to fly and keep pressing AF-On throughout the sequence until the bird has flown out of the frame. (I don't use 3D focus because I have not had good luck with it when photographing fast-moving or jerky-jerky subjects.) The bird flies parallel to the sensor plane, and I have a clear, unimpeded view of the bird across the entire frame. I have read the relevant section of Steve's autofocus book many times, and it seems that my settings and technique are correct and the camera should retain correct autofocus throughout the sequence, but typically only the frames with the bird still perched and maybe a couple of frames right after takeoff are acceptably sharp; the rest are unsharp. What am I doing wrong?

I'd expect any of the Dynamic Area modes, especially the larger ones to struggle with a situation like that. The problem with the dynamic area modes is that the focus point in the center of the selected grouping carries extra priority and is checked more often than the surrounding points. That means that if you don't do a pretty good job of keeping the center focus point of the group on your desired focus target (e.g. the bird's eyes) during the shot it's likely that another high contrast point (e.g. the background) will end up under that central focus group point during the burst of shots and the focus will shift to that alternative high contrast target. IOW, Dynamic Area modes work best when you're actively tracking the subject and doing a pretty good job of keeping the central point of the selected group on your desired target. Additionally Dynamic Area modes tend to work best with the smallest practical number of points selected and the larger the group gets the higher the probability that some other high contrast element in your frame will grab focus, and with a static camera once it grabs on a high contrast element it will tend to stay there.

I tend to think of Dynamic Area modes as Single Point with margin for error built in. How much margin for error depends on the size of the group but it still behaves a lot like Single Point in the sense that you really do want to keep the center of the selected area on top of your preferred focus target.

Personally in a situation like what you describe (a bird taking off in a known direction) I'd try to pan with the bird and not frame statically and or use Group AF assuming there's not foreground clutter as Group AF will prioritize image elements closest to the camera.

 

[Steve]

Here's a situation where I have not had good luck retaining focus, and I don't know why:

A bird is perched and getting ready to fly. I want to keep the camera fixed and immobile on a tripod and let the bird fly across the frame using a large number of focus points while tracking focus — dynamic 153 setting on my D500 or D850. While the bird is still perched, I position it on the side of the frame to allow it to fly across the frame after takeoff. I press to begin focus (back button focus) when the bird is getting ready to fly, and I continue to press AF-On throughout the sequence until the bird has flown out of the frame. (I don't use 3D focus because I have not had good luck with it when photographing fast-moving or jerky-jerky subjects.) My typical a3 Focus tracking with lock-on settings in this scenario are Blocked shot AF response 3, Subject motion midway between Erratic and Steady. The bird flies parallel to the sensor plane, and I have a clear, unimpeded view of the bird across the entire frame. I have read the relevant section of Steve's autofocus book many times, and it seems that my settings and technique are correct and that the camera should retain correct autofocus throughout the sequence, but typically only the frames with the bird still perched and maybe a couple of frames right after takeoff are acceptably sharp; the rest are unsharp. What am I doing wrong?

That's an incredibly tough scenario for the camera. As DR says, I find it's best to pan. I honestly think in a scenario like that the camera's processor just isn't fast enough to keep up. I've run across that same situation countless times and it's always a challenge. Plus, with the camera still, you need a LOT more shutter speed than normal as well. When you pan, you help keep the bird in the same relative area of the frame. Without panning, it's moving incredibly fast and 1/4000th or faster is often called for.

In a situation like you describe, sometimes I'll prefocus, drop to F/8 or F/11, and crank up the shutter speed. You need SERIOUS light to do this of course, but if the bird stays parallel to the camera, it can work. However, I only use that technique for really fast birds. For normal birds, I pan.

Also, when you have sudden starts or stops, "Erratic" is the best setting. Although, I don't think it'll help too much.

 

[OohMatron]

D153 uses so any points it is almost by definition slower to respond to changes. There is so much more processing and computation necessary within the camera. Use less points, 21 max, ideally 9. If that fails, it is time to refine your panning and tracking skills by practising.

 

[Gary Shackelford]

I'd expect any of the Dynamic Area modes, especially the larger ones to struggle with a situation like that. The problem with the dynamic area modes is that the focus point in the center of the selected grouping carries extra priority and is checked more often than the surrounding points. That means that if you don't do a pretty good job of keeping the center focus point of the group on your desired focus target (e.g. the bird's eyes) during the shot it's likely that another high contrast point (e.g. the background) will end up under that central focus group point during the burst of shots and the focus will shift to that alternative high contrast target. IOW, Dynamic Area modes work best when you're actively tracking the subject and doing a pretty good job of keeping the central point of the selected group on your desired target. Additionally Dynamic Area modes tend to work best with the smallest practical number of points selected and the larger the group gets the higher the probability that some other high contrast element in your frame will grab focus, and with a static camera once it grabs on a high contrast element it will tend to stay there.

I tend to think of Dynamic Area modes as Single Point with margin for error built in. How much margin for error depends on the size of the group but it still behaves a lot like Single Point in the sense that you really do want to keep the center of the selected area on top of your preferred focus target.

Personally in a situation like what you describe (a bird taking off in a known direction) I'd try to pan with the bird and not frame statically and or use Group AF assuming there's not foreground clutter as Group AF will prioritize image elements closest to the camera.

Thanks, very much, and thanks to Steve also, who I see has read your reply. I'll try harder! BIF can be a real challenge.

 

[DRwyoming]

BIF can be a real challenge.

Agreed, but it's a great challenge and when it works it can be very rewarding in part because of that challenge

I don't know what lenses you're running nor what kinds of birds you're trying to capture but FWIW:

- If possible with your gear try hand holding when first learning to pan and track BIF images. That can help if you're using moderately sized lenses but isn't really a very good option for really big glass but at least when you start it's good to have more freedom than you'd get with a tripod mounted rig. If that's not possible a full gimbal mount, half gimbal mount (e.g. Sidekick) or perhaps a monopod with a decent head are much better for learning how to track BIF than most pure ball head setups.

- Start with bigger slower moving birds that fly more predictably before working towards smaller more erratic birds. If you can get used to smoothly panning bigger birds like Herons, Egrets, Hawks and soaring birds it gets easier to work down towards Gulls or Ducks and then the real challenging stuff like Swallows and Flycatchers. Starting with the small erratic birds can be really frustrating. One exception is Hummingbirds that aren't too bad if you catch them hovering near a flower or feeder but most smaller birds and especially the mid air insect hunters can be really challenging and not a great place to start.

- I'd suggest starting with Group AF on Nikon cameras unless your shooting environment has a lot of close in objects that can fool Group AF. It tends to be more forgiving for flying birds though you do have to be careful anytime you pan past objects closer than the bird or the bird turns a bit and the wings are a lot closer than the head and eyes (though often that means the bird is flying away from you so maybe it's time to stop capturing images ). If that's not working then try the smallest Dynamic AF group that you think you can still keep over the bird's eye or neck most of the time and work towards smaller Dynamic areas as your tracking skills improve.

- Since you generally want to give a bird plenty of room to fly into the frame and it's not unusual to do some cropping for BIF images it often makes sense to start by using the center focus point in either Group AF or one of the Dynamic AF modes. It tends to be the most sensitive AF point in falling light conditions and since you may have some birds flying left to right and others going the opposite direction it's a pretty good middle of the road solution that works in a lot of cases. As your tracking skills improve you can start doing more dynamic composition on the fly by choosing other parts of the frame where you'd like to place the eye but starting simple can help and can work well for a lot of BIF images.

Good luck and post some results in the BIF thread.

 

[pochito]

Interesting explanation, thanks DRWyoming.
I'm still struggling with autofocus and what you write on Dynamic Area makes sense to me.
So far I was not befriended with Group AF, my success quota is low. But I admit that there are many factors for that, including my inexperience.
I'll try it with that in mind