Back button focus (BBF) - to hold our not hold with stationary target?

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Eldon

Eldon

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Shooting D500 for wildlife, I use BBF exclusively. I was double checking tripod based fine tuning for lenses (500PF & 70-200 zoom) done a couple years ago. Decided to shoot handheld as that is what I will be doing in the field. It works well for me to shoot on CH with short burst for moving targets. For birds, sometimes I shoot in bursts even if stationary in case of small movements or they decide to fly.

But in testing with a stationary object (manual, auto-ISO, f5.6 & 1/500) I noticed that sometimes not all the images maintain focus if I hold down AF-ON button. I get much better results with stationary target if I press and release AF_ON button before activating shutter.

Has anyone else experienced this? Is it just my own movement that is causing the issue or something else? Should I discontinue holding down AF-ON with stationary and forego possible BIF opportunity?
Thanks, Eldon
 
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I tend to shoot in small bursts as well, even for stationary subjects.

While I haven't noticed a difference between holding and releasing AF-ON for stationary targets, I think I actually tend to "burst" with focus too. That is, I'll constantly release it and hold it down for a few shots, essentially allowing the AF to reacquire lock every few shots. I think I picked this habit up from shooting in low light with older bodies when the AF had an especially difficult time locking on, sometimes it would take a few tries, and it has just become habit I guess...even with newer bodies, better lenses and brighter light. I think Steve might have had a video suggesting a technique similar to this for tough AF targets. Maybe he'll chime in?

Of course, when the bird takes flight or the action starts, I absolutely hold down AF-ON and fire away!

-Frank
 
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Eldon S. said:
Has anyone else experienced this? Is it just my own movement that is causing the issue or something else? Should I discontinue holding down AF-ON with stationary and forego possible BIF opportunity?
Click to expand...
I suspect it's related to your own movement assuming your target is in decent light and the focus isn't struggling.

In terms of hand holding while doing focus fine tuning, I've definitely heard the argument about shooting the way you will in the field (e.g. hand holding) but the issue I see is that you really want the sensor plane and camera to be parallel to your target and maintain that throughout all your focus adjustment test shots. For that reason alone I always do focus fine tuning with the camera mounted on a tripod. I still run high shutter speeds to minimize camera shake issues but I definitely don't want any skew in the sensor plane vs the target plane which can lead to inconsistent focus tuning results. It also makes it easier to compare a series of test shots as there should be minimal to no changes in the target alignment which is hard to assure when shooting hand held.

In terms of your question, if I'm doing focus and recompose shooting with stationary subjects then of course I release the BBAF before recomposing and shooting. But if I'm keeping the focus point, say in Single point mode right on something like a bird's eye I'll keep holding down the AF-ON buton so that it adjusts to slight head movements and keeps the eye sharp.
 
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One other point to consider; when testing lenses it is important to remove as many variables as possible...while you shouldn't have any issues getting sharp shots at 1/500 with the 70-200, it is close to the limit with the 500PF, especially handheld with VR off. It might be worth it to shoot at higher shutter speeds to eliminate camera movement as a potential issue, and to also keep the iso consistent for the sake of shot to shot comparison and consistency.
 
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Eldon S. said:
Shooting D500 for wildlife, I use BBF exclusively. I was double checking tripod based fine tuning for lenses (500PF & 70-200 zoom) done a couple years ago. Decided to shoot handheld as that is what I will be doing in the field. It works well for me to shoot on CH with short burst for moving targets. For birds, sometimes I shoot in bursts even if stationary in case of small movements or they decide to fly.

But in testing with a stationary object (manual, auto-ISO, f5.6 & 1/500) I noticed that sometimes not all the images maintain focus if I hold down AF-ON button. I get much better results with stationary target if I press and release AF_ON button before activating shutter.

Has anyone else experienced this? Is it just my own movement that is causing the issue or something else? Should I discontinue holding down AF-ON with stationary and forego possible BIF opportunity?
Thanks, Eldon
Click to expand...
I've noticed it, usually because I am moving the camera. Obviously if you release the BB the focus stays locked.
 
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FHaluska said:
One other point to consider; when testing lenses it is important to remove as many variables as possible...while you shouldn't have any issues getting sharp shots at 1/500 with the 70-200, it is close to the limit with the 500PF, especially handheld with VR off. It might be worth it to shoot at higher shutter speeds to eliminate camera movement as a potential issue, and to also keep the iso consistent for the sake of shot to shot comparison and consistency.
Click to expand...
Can I ask why you would shoot handheld with the VR off?
 
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Capturingtheunseen.com said:
Can I ask why you would shoot handheld with the VR off?
Click to expand...

You might not, but the OP didn't specify if VR was on or off so I figured I would mention it for clarity.

Also, VR/lens sharpness gets tricky at higher shutter speeds. Depending on the lens, it is often recommended to turn off VR at speeds above 1/500 or 1/1000, as some people feel that the VR system stops removing motion, and starts adding motion as shutter speeds increase above this threshold. I definitely found this to be the case with my 200-500, though not as much with my 500G. While 1/500 is probably fine (and useful) to have VR on, he didn't specify the shutter speeds he was using when in the field. Perhaps he was using higher shutter speeds with VR? Just something to think about...as if we need more of that!

Similarly, depending on your support system, even at slower speeds, the best results can sometimes be had with VR off, even with lenses that have Tripod mode. And Nikon recommends turning it off when doing and AF tuning.

Basically, I was just reminding the OP to consider VR when it comes to critical sharpness.

-Frank
 
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FHaluska said:
Awesome. One less thing to think about! What lens(es) do you use? I take it you don't see any softening or (inconsistently sharp images) at high shutter speeds?
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I use the Nikkor 200-500mm 5.6. If the image is soft--which doesn't happen often--it's because I missed getting the focus point on the bird. Here is a tight crop at 1/4000. The VR on this lens is excellent, good for 4.5 stops.

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Capturingtheunseen.com said:
I use the Nikkor 200-500mm 5.6. If the image is soft--which doesn't happen often--it's because I missed getting the focus point on the bird. Here is a tight crop at 1/4000. The VR on this lens is excellent, good for 4.5 stops.
Click to expand...

Good info. Yes, I had the 200-500 for a while, and you are right, the VR is amazing on that lens. For me I found that I had SLIGHTLY sharper results turning off the VR at shutter speeds over 1/2000. From 1/1000-1/2000 it was hard to tell - sometimes I thought it made a difference, sometimes I thought I was just seeing things - and below 1/1000 definitely VR on. In practice I tried to turn VR off when I knew I'd be above 1/2000. Maybe it was just my copy of the lens? Or my shooting technique?

Nice Osprey, BTW!
 
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Eldon S. said:
Shooting D500 for wildlife, I use BBF exclusively. I was double checking tripod based fine tuning for lenses (500PF & 70-200 zoom) done a couple years ago. Decided to shoot handheld as that is what I will be doing in the field. It works well for me to shoot on CH with short burst for moving targets. For birds, sometimes I shoot in bursts even if stationary in case of small movements or they decide to fly.

But in testing with a stationary object (manual, auto-ISO, f5.6 & 1/500) I noticed that sometimes not all the images maintain focus if I hold down AF-ON button. I get much better results with stationary target if I press and release AF_ON button before activating shutter.

Has anyone else experienced this? Is it just my own movement that is causing the issue or something else? Should I discontinue holding down AF-ON with stationary and forego possible BIF opportunity?
Thanks, Eldon
Click to expand...
Here's what I have found with my Nikkor 200-500mm lens on the D7500: Especially with small birds where the focus point is large enough to also have some of the foliage around the bird in the focus square, the focus will sometimes jump from the bird to the foliage, resulting in either front- or back-focus. This is going to be especially likely when hand-holding a long zoom lens. In cases like those sometimes it can help to use Dynamic 9-point AF-C for more consistent focus. If this focus jumping to the foliage happens a few times I'll generally touch the back button once and check focus. If not sharp I try again until it's locked solidly, then stay off the back button while shooting, only re-focusing when the bird moves on its perch, like shifting on the branch. An adequate aperture setting can help compensate for small bird movements.

With larger birds where you can get the entire focus point on the bird, focus can hunt when there's insufficient contrast for the camera to focus on. If the entire image under the focus point is of even lighting and color this can cause focus to hunt. I found this out the hard way trying to shoot the moon with single point AF-C or even AF-S. The moon's surface is so evenly lit and devoid of contrast that focus is problematic. One night I used 9-point dynamic and got a pin-sharp image because one of the surrounding focus points picked up the contrast between light and black on the outer edge of the moon.
 
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FHaluska said:
Good info. Yes, I had the 200-500 for a while, and you are right, the VR is amazing on that lens. For me I found that I had SLIGHTLY sharper results turning off the VR at shutter speeds over 1/2000. From 1/1000-1/2000 it was hard to tell - sometimes I thought it made a difference, sometimes I thought I was just seeing things - and below 1/1000 definitely VR on. In practice I tried to turn VR off when I knew I'd be above 1/2000. Maybe it was just my copy of the lens? Or my shooting technique?

Nice Osprey, BTW!
Click to expand...
Thanks. I would say do what works for you. Some people like to have it on, some have it off. What you like is what matters.
 
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