Back button focus , disables lateral tracking off center point?

Im just learning of this back button focus procedure, It appears to be a convenient way to lock focus after the autoF has chosen a distance, or conversely, if one doesnt release the rear AF button , the camera continues to search continuously at the main (center) focus point.
((The focus priority should? - or is ? disabled in favor of shutter release priority . It seemed last night that focus acquisition was still required to release the shutter.))

Now, if one is using one of the 'area' focus modes , that is to say d51 d9 d21 or 3d , Im thinking these would also be disabled because the camera would never actually select a permanent target point to hold in focus,, is that correct?
So if I want the camera to assist me by locking on temporarily to an object both moving toward or away ,, and at the same time laterally off the center focus point,,, it can no longer do this- in the back button focus configuration, right?

And this seems might be true as well if one turns the focus lock period to its slowest , off , level. ,, because the focus would remain 'locked in' for a duration of zero. Is that right? , the focus lock must be more than zero to track ?

Or is it that in single point D51 the camera is just not tracking predictively anyway?

To fully use the technique, menu A-1 is set to release priority. Other wise if you were to keep it focus priority, releasing the back button and recomposing might not allow the camera to fire since it does not see focus.

Whether you are using back button or shutter button, the area modes should work the exactly same as long as the back button is held down. So the only question I see is menu A-1, release or focus priority. If there is action that you need to catch, you will be holding down the back button full time anyway. In effect, the same as if you were using the shutter button. Back button discussion aside, some people prefer af-c with release priority anyway for fast action. The thinking is hopefully subject is in reasonable in focus when shutter fires. The alternative is you are in focus priority and get no shot at all if the action is too fast. So I'm with the release priority crowd.

I've only been using the back button steadily for a few months, but that's my thoughts. mainly I am using single point. For the area modes, I would likely be holding the back button down full time anyway, so its just like using the shutter button. that way the area modes can continue to do their thing as usual up to shutter release. As I see it, releasing the back button to hold focus is something I would only want to do with single point focus anyway.

I would keep the delay (A3) thing off unless I have some compelling reason to keep it on. For instance, you are panning on some sports action and there are some light poles you will be panning across. The delay would ignore that. Otherwise it is a nuisance and you should keep it off so there are no delays in keeping up with the action.

Ok , well if that release priority isn't somehow required other than you mentioned Ill give it a try this weekend. ( My personal aim is really to get more tack sharpness in my photos, I'm not happy with soft shots at all , though I understand that under some circumstances a soft shot is basically fine as long as you get the shot) . Thanks

Stoshowicz said:

Ok , well if that release priority isn't somehow required other than you mentioned Ill give it a try this weekend. ( My personal aim is really to get more tack sharpness in my photos, I'm not happy with soft shots at all , though I understand that under some circumstances a soft shot is basically fine as long as you get the shot) . Thanks

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I use BBF (Back Button Focus) on my D7100 with D9 most all the time. I use AF-C with Priority Selection set to "Focus" most of the time but also use "Release" pretty regularly. I've not had issue getting or keeping a focus-lock using either setting. That being said, I don't shoot a lot of sports, or fast-action type stuff so your mileage may vary. What I've learned is that getting"tack sharp" photos out of the D7100 requires really good glass first and foremost. Then, if you haven't checked your preferred lens(es) for front/back focus, you need to. I found most all of my lenses needed some tweaking using the AF Fine Tune menu option in the Setup Menu which helped dramatically with some of my lenses and I *do* mean "dramatically*. I also use ISO 200 except under the brightest of bright conditions and faithfully abide by a shutter speed twice that of the focal length (eg. when shooting at 100mm shutter speed is not less than 1/200). That's a big part of why I shoot at ISO 200, there's no discernible noise and it helps keep your shutter speed bumped up a little bit, even at smaller apertures.

Maybe something in there will help you...

....

Horoscope Fish said:

I use BBF (Back Button Focus) on my D7100 with D9 most all the time. I use AF-C with Priority Selection set to "Focus" most of the time but also use "Release" pretty regularly. I've not had issue getting or keeping a focus-lock using either setting. That being said, I don't shoot a lot of sports, or fast-action type stuff so your mileage may vary. What I've learned is that getting"tack sharp" photos out of the D7100 requires really good glass first and foremost. Then, if you haven't checked your preferred lens(es) for front/back focus, you need to. I found most all of my lenses needed some tweaking using the AF Fine Tune menu option in the Setup Menu which helped dramatically with some of my lenses and I *do* mean "dramatically*. I also use ISO 200 except under the brightest of bright conditions and faithfully abide by a shutter speed twice that of the focal length (eg. when shooting at 100mm shutter speed is not less than 1/200). That's a big part of why I shoot at ISO 200, there's no discernible noise and it helps keep your shutter speed bumped up a little bit, even at smaller apertures.

Maybe something in there will help you...

....

Click to expand...

That sounds like nice reasonable methodology , Im using a 70-300 vr lens which , looking at my static pix , is spot on though,, most of my subjects are small , and so I dont want to move the front-back focus adjustment at all. In order to get enough shutterspeed and aperture , I often have to boost the Iso topping out at 800. The issue I'm trying to improve ,, becomes complicated , as the dragonfly gets closer I get better detail , but I've got to be super quick to acquire focus, and its just difficult to get a clear grasp of the intricacies of the various auotofocus systems . Its just confusing.. and one really needs the camera to help out.
For instance -I was reading on luminous landscape Mr Koerners post , where he said, that
"Setting multiple AF sensors with the focus tracking lock on set to 'off' will defeat the camera's dynamic AF capabilities - multiple AF sensors are designed to work with long, short, or normal settings to keep contact with the subject. If you are using a single AF sensor on a single subject, OFF may be appropriate under some circumstances - if you loose contact with the subject however the AF will instantaneously jump in most cases to the background." and the D51 mode might be more prone to this.And I just dont know if this is meaning single point D51 , or if its AF-S single point.. so I cant say if this agrees with the earlier post by nickt , or disagrees with it- regarding the autofocus lock.

Another issue that pops up is, 'what exactly is the delay that might happen using 51point mode versus nine point mode?' Wouldn't more autofocus points be an improvement?
Simply put ...
The recipe Id like to know is what combo acquires the small moving target fastest , locks on and holds on to it best , for the fraction of a second until the shutter completes its closure.

Uggh

Stoshowicz said:

For instance -I was reading on luminous landscape Mr Koerners post , where he said, that
"Setting multiple AF sensors with the focus tracking lock on set to 'off' will defeat the camera's dynamic AF capabilities - multiple AF sensors are designed to work with long, short, or normal settings to keep contact with the subject. If you are using a single AF sensor on a single subject, OFF may be appropriate under some circumstances - if you loose contact with the subject however the AF will instantaneously jump in most cases to the background." and the D51 mode might be more prone to this.And I just dont know if this is meaning single point D51 , or if its AF-S single point.. so I cant say if this agrees with the earlier post by nickt , or disagrees with it- regarding the autofocus lock.

Click to expand...

I think I understand his point. I can see how 51 pts might get distracted and maybe that delay would be helpful. I think it could happen with single point too. I can't remember exactly what I did, but I convinced myself that having a delay set was detrimental to keeping focus on a bird. Also detrimental to keep track on my kid when she was playing field hockey. I have no hard data for you though. I'm usually in single point or 9 point and I have shied away from 51pt. I think the issue was when the subject was heading towards me. I can't remember, lost brain cells, lol. I'm pretty sure that delay keeps af-c from making a correction too soon once focus is acquired. This could be fine for side to side movement, but not good for a subject charging at you.

I understand your angst. Its tough to wrap your mind around the intricacies of the Af system. I keep a copy of this handy and re-read it often:

http://alexdanev.com/forum/Books/nikon/D7000_AF_Explained.pdf

Its for the d7000, but the principles are the same.

I just set mine up for back button focus today and toyed with single, 9, 21 and 51 to see what I liked. I have almost always used single point but for some reason I chose 9 today. Glad to see that I probably chose correctly.

Horoscope Fish said:

I use BBF (Back Button Focus) on my D7100 with D9 most all the time. I use AF-C with Priority Selection set to "Focus" most of the time but also use "Release" pretty regularly. I've not had issue getting or keeping a focus-lock using either setting. That being said, I don't shoot a lot of sports, or fast-action type stuff so your mileage may vary. What I've learned is that getting"tack sharp" photos out of the D7100 requires really good glass first and foremost. Then, if you haven't checked your preferred lens(es) for front/back focus, you need to. I found most all of my lenses needed some tweaking using the AF Fine Tune menu option in the Setup Menu which helped dramatically with some of my lenses and I *do* mean "dramatically*. I also use ISO 200 except under the brightest of bright conditions and faithfully abide by a shutter speed twice that of the focal length (eg. when shooting at 100mm shutter speed is not less than 1/200). That's a big part of why I shoot at ISO 200, there's no discernible noise and it helps keep your shutter speed bumped up a little bit, even at smaller apertures.

Maybe something in there will help you...

....

Click to expand...

Stoshowicz said:

Simply put ... The recipe Id like to know is what combo acquires the small moving target fastest , locks on and holds on to it best , for the fraction of a second until the shutter completes its closure.

Click to expand...

First of all you are going to have to come to terms with the fact that most often there is not going to be a specific, magic recipe that is going to work for your specific situation every time. Really good photography is hard work and a good deal of it. You have also chosen some difficult subject matter in Dragonflies.

Let me see if I can't boil down the whole focus point settings thing for you.

Simply put:

• For a very fast moving subject moving erratically, use the maximum number of points, i.e. D51.
• For subjects moving fast, but predictably enough you can track them accurately use fewer points; i.e. D21.
• For slow moving targets that are easily tracked use even fewer focus points; i.e. D9
• For stationary targets, since you have all the time in the world to fuss with focus, use even fewer; i.e. Singe Point. That, or do like I do and continue to use D9.

Also, nickt linked you to an article called "D7000 Autofocus Explained". Don't be fooled by the title, the AF-Modes and and AF-Area Modes of the D7000 are the same AF-Modes and AF-Area Modes used on your camera. The principles explained are universal across the Nikon-camera universe. Read that article as many times as you need to fully grasp everything it's explaining.

Also know that you're going to have to learn what all the different tools are, how each one works individually and how each one harmonizes with all the others. There are not going to be any easy outs or magic recipes you just "dial in" that nail the shot every time. You're going to have to apply your understanding, see what works and what isn't and go from there. It's what we all do because that's the nature of photography.

....

I know exactly what you mean about convincing onesself thats so easy to do. Anywho , I went ahead and gave the technique a rigorous tryout this weekend ,, and my verdict is ... Its really great, I wish I'd always had been doing it , and I dont know why it isnt the default setting on SLRs. I had the focus lock ON set to its longest, In D51 ( for worst case scenario) Heck that camera followed birds right down into the grass, snagged dragonflies as easily as ever and just in general got suck a nice solid focus lock on everything, and stayed 'on distance' for a donkey that had his head down for several minutes and only briefly raised it. Id say its a tad more stubborn about shifting from one target to the next , as you'd expect, but other than that I was really impressed at what the camera could actually do.
Thanks for the tips.View attachment 113140