Question on D810 and use of AF-ON

Discussion in 'Nikon' started by bennett_richards, Aug 27, 2014.

  1. I just got a D810 and I have never used a AF-ON button before. I am not sure what it does.
    I started in the days of manual everything cameras and my habit is to see a subject ( I do street photography) place the central focusing
    area on that subject, press the release 1/2 way to freeze the focus and exposure for that subject, re-compose and then hit the shutter
    release.

    How would I incorporate the AF-ON button into that workflow? I seem to be hearing that a camera as sophisticated as the D810 can allow
    you to set focus on a subject, recompose and then follow that subject if it happens to move.... WOW. How would one set that up with the
    D810?

    Thanks
     
  2. Using the AF-ON button is much better than having the shutter release activate AF, especially with AF-S lenses. Focus tracking is indeed wonderful. Set your camera to continuous AF, then press and hold the AF-ON button to lock focus on your subject. As your subject moves, the camera's focus points will follow. I use this all the time on trains with my ancient D700 and it works fine generally. With the D810, follow focus should be exceptional.
     
  3. I'm afraid AF-On is not a viable option for the way you describe you want to take your pictures, i.e. focus on subject and freeze it by pressing the release button (or AF-L button for that matter), recompose (ie put your AF focus area on a different spot) and expect that the AF will track the movement of your subject despite the before mentioned.
    You may have initially focused on your subject initially and frozen it on the spot where it was at that moment, but by recomposing the camera will indeed focus in that area (i.e. the focal plane on which the focus has been frozen), but due to the recomposing will not recognize any subject (let alone the one you originally focused on) and have no idea what to base it calculation for the focus of the next spot on.
    Of course still using the AF-On button while recomposing is no solution as the camera will then refocus on whatever then comes in front of the AF focussing area.
    As mentioned, (although preference on whether using AF-On in combination while still using AF on the release button, or completely disengaging AF from the release button and only having it with the AF button may vary), if you lock AF on a subject, keep your AF area on the subject, and next shoot a series of pictures of it moving, using the AF button is an option worth considering,, as the camera will have an idea of what the subject is that was in focuses and has to be tracked.
    Personally I have used/still use the AF-On button combined with AF on the release button when eg shooting surf, in particular with long (400 to 600mm) lenses with TC's. I then constantly push the AF button to keep focusing while I'm looking through the viewfinder and follow the surfer in anticipation of a possible action. When the action indeed unfolds I then have my camera already in focus for the first shot (rather then missing the often decisive split second it would otherwise the the camera to acquire focus and make it regularly miss the correct focus) and have a good starting point for the following series of shots where I have to rely on the focus tracking to get the pictures sharp.
    My first suggestion would be not to restrict yourself only to the central AF area, but when making the 'perfect' composition use the one closest to the subject and focus with that one. Given the relative small area the 51 AF points cover, this might compromise your composition, but the 36 megapixel sensor (I have a D800) in my experience allows plenty of space for cropping without too much loss of IQ.
    Theoretically 3DAF may offer another solution (never used it personally and don't intend to), but the problem is that the camera will then completely autonomously decide what to focus on, although feedback is quite positive on its ability to then follow the subject when it moves.
     
  4. I've just started practicing using this feature, and now I'm totally confused Paul. I've watched you tube video's and for the most part they all say it's the best way to focus, action or still's. They did mention a learning curve. The one thing I noticed was that in AF-C mode the little focus square is moving around and doesn't like to settle on something right away, so you wait a second till it calms down, then press the shutter. That's why I guess they say practice.
     
  5. Kyle Bybee [​IMG], Aug 28, 2014; 06:10 a.m.
    The one thing I noticed was that in AF-C mode the little focus square is moving around and doesn't like to settle on something right away, so you wait a second till it calms down, then press the shutter. That's why I guess they say practice.

    AF-C has nothing to do with the focus area, it simply is an option to either have the camera focus all the time the release button/AF-ON button is pressed, or, in the case of AF-S, to have the camera lock to focus on whatever subject you aim at while pressing the release button and only refocus either after the shot is taken, or after the release button is let go and pressed again for a new cycle of focusing.
    The description you give of what you saw on the video matches what happens in 3DAF Tracking option, where you push the release button, and the camera next, based on it's software, decides what to focus on, independently of what you might prefer.
    The review of the D800 on DP review, page 15 http://www.dpreview.com/reviews/nikon-d800-d800e/15 shows exactly what is shown in your LCD while selecting the AF area mode, and even has an example of shooting with 3D AF tracking.
    IMO the many (and consequently confusing) options for selecting the for you 'right' AF setting is the reason for needing practice since like any computer the camera will only do what is it is programmed to do. So you will need to find out what the preferred setting for you type of shooting is, and I of course can only try to give some tips based on what worked for me when taking pictures of moving subjects.
     
  6. Regarding focus-and-recompose, it is possible to focus using, say, the central point, keep the camera in AF-C, and pan the camera to your desired framing with focus still engaged (either via AF-On or via the shutter release). If you're lucky, the camera will track the focus to other focus points (because there's no difference between moving the camera and the subject moving in front of it). Where this struggles is when the subject you're trying to focus on falls outside the range of the camera's AF sensors - at that point, there's not much it can do to try to maintain focus.

    AF-On is very useful for circumstances where the camera might be struggling to pick the right subject. Use AF-On to focus where appropriate, and release it with the camera's focus in what is hopefully the right position (unless you or the subject moves) when needed. Where possible, I tend to try to keep the subject under a focus point (I usually move the focus point manually) and keep AF-C enabled, so that small movements are tracked. Bear in mind that rotating the camera to recompose does move the focus plane, sometimes by enough to affect where you should have been focussing. Remember you're in this mode if asking someone else to use the camera or if - as I was recently - you're trying to take a photo "blind" (waving the camera over your head) - I'd remembered to switch to 3D area focus, but forgot that I only had AF on the AF-On button. Beautifully composed but out-of-focus image of people on Capilano suspension bridge. Embarrassing.

    You might also like to play with the "AF-On combined with release mode: focus" combination that allows trap focus (the camera will shoot only when something crosses the focal plane - and for long enough for the camera to notice, of course). Enjoy!
     
  7. Maybe I am missing something, but have never understood why using an AF-on button is better than a half press of the shutter button to activate the AF system.
    Yes, I can see the occasional use of separating AF and AE, and/or manual manipulation of either or both of those functions. But, normally, if I have my AF settings optimized for what I am shooting, AF operation (from the half press shutter button) is not much of an issue for me. Less awkward, IMO.
    Now, when the AF system becomes clairvoyant and can read my mind for the ideal AF spot anywhere on the image, and track that rapidly and accurately, that will be something.
     
  8. Call me an old Luddite, but I've never seen the point of the AF-ON button either; certainly never used it in anger and am quite happy forgetting it exists. First pressure on the "GO" button works fine for me, and in fact I find it a pest if the camera suddenly and unbidden decides to follow focus. As for using auto AF points - Yikes, that's a definite step too far! Gimme the single centre AF rectangle every time. Or at most a single point I can steer around the screen, except that usually takes far more time and effort than the "focus and recompose" method.
    So just because it's there Bennett, that doesn't mean you have to use it.
     
  9. Maybe I am missing something, but have never understood why using an AF-on button is better than a half press of the shutter button to activate the AF system.​
    I became a convert a few years ago and now use the AF-ON button exclusively - I would not consider purchasing a camera that doesn't have one or at least allows for a properly placed button to be re-programmed.
    The advantage to me is that I don't have to select between AF-C and AF-S by moving that particular selector on the camera (I still shoot with D300 and D700) - I get the desired behavior by having the camera always in AF-C and either keeping the AF-ON button pressed for continuous focus and tracking or by releasing the AF-ON button to stop focusing and maintain focus on a previously selected area. Best of two worlds!
    Never had to use the AE-L/AF-L button and the times where I accidentally was in AF-S when I should have been using AF-C are over. Just need to remember to press that shutter button half-way to activate VR!
    Never got a hang of the focus/recompose method - which I consider a relic of the time when there were only three or five AF areas in the viewfinder - and sadly it becomes a necessity again with FX cameras. Got spoiled by 51 in the D300 that cover enough viewfinder area to always be able to select one to fall onto the area I wanted to focus on. On any FX camera, coverage is reduced and I find myself needing to focus and recompose more often.
     
  10. Focus and recompose: The technique is sort of a relic of rangefinder cameras really (showing age here), but still functional, ha ha.
     
  11. I use both shutter focus and AF-On focus. Normally I use shutter focus until just after the first time I find myself trying to focus on a difficult moving subject in bad light, at which point I remember that AF-On focus would let me lock. I then use AF-On focus until just after the time I'm trying to take a photo and can't get at AF-On (either because I'm shooting at a weird angle, using an external release or handing the camera to someone else). I normally only remember to use the other mode just after the previous one has annoyed me... It's unusual for me to use single-shot AF - normally either I or the subject are likely to move enough just by swaying slightly that I don't trust the focus, and the focus mode selector is in my least favourite place on the camera, since I'm a fan of hand-holding big lenses. (Generally the only thing I use the mode selector button for is a source of swearing when image review cancels because I've accidentally hit the button with the side of my thumb. It's quite good for making the camera appear to have locked up, too.)

    Focus and recompose - especially with the central focus point and a significant shift - is fine at f/16 on 35mm film, and asking for a lot of trouble at f/1.4 on a 36MP sensor (and bear in mind you're probably not getting 36MP if you're shooting at f/16, even if you don't mind cloning out dust spots). Not just because the focal plane shifts - there's often a bit of focal plane curvature to worry about. I'd always at least use the nearest focus point before shifting, and if I'm outside that, I'll use live view if I can. With a distant - especially fast-moving - subject and a smaller aperture (such as the 300 f/4 + TC14 I was using for whale watching last week - I like holidays!) I'm less fussy, and would focus close with AF-On, then trust to the depth of field.
     
  12. The one thing I noticed was that in AF-C mode the little focus square is moving around and doesn't like to settle on something right away, so you wait a second till it calms down, then press the shutter. That's why I guess they say practice.
    The description you give of what you saw on the video matches what happens in 3DAF Tracking option, where you push the release button, and the camera next, based on it's software, decides what to focus on, independently of what you might prefer.​

    Not really; it's the Dynamic Single Point AF mode, not necessdarily the 3D one (which tends to be sluggish), where the AF can change AF points based on colour/contrast, adjacent to the AF point you manually selected. It is not at all independent of what you prefer (that is the full auto mode where you do not even select any AF point, camera does it all). Single point dynamic is AF tracking and really quite predictable. The jumping around is normal, especially with long lenses hand-held - it's the AF point stikcing to your subject.
    Personally, I like AF-On in combination with AF-C and Dynamic Single Point AF for tracking sports or wildlife. I do not use it an awful lot, but it's an option I do not mind having. That said, would it not exist on my camera, I'd be equally fine, the half-press routine also works fine for me.
    Focus and recompose - since I often like very wide apertures too much, I really stopped using it - it's only a valid technique with sufficient depth of field, in my view. But with the very wide apertures, I'm using manual focus anyway; with a good viewfinder often faster and easier than making one of the outer AF points work with shallow DoF.
     
  13. With practice, it becomes second nature to use the thumb to control focus with AF-ON (at least on my D300), and the index finger on the shutter release, it is not really much different from doing the half-press to focus, and then the full-press to trigger the shutter. Using the AF-ON button and setting the AF mode to AF-C, gives you instantaneous control over AF-C, AF-S or AF-M without using any other button except the AF-ON. If you don't press the AF-ON, no change in focus, or you can use manual focus on the lens. If you press AF-ON and release, you get AF-S. If you keep AF-ON pressed, you get AF-C. You don't have to worry whether you accidentally let the half-press go, particularly when you want to reselect what your exposure was also based on. It is great to have exposure and focus decoupled.

    I too am from the old MF days, and if there is sufficient DoF, I too fallback to focus and recompose as my preferred method, since it saves having to twiddle with moving the focus point around. It works just fine with the AF-ON button.
    As others have said, AF-C and subject tracking is exactly the same whether you use the half-shutter press or the AF-ON button to engage the AF system. The difference is that the AF-ON button puts you in control of when the AF system is engaged, whereas with the half-press you have no choice but to engage the AF system before the shutter activates unless ou have set a second button to choose manual focus.
     
  14. Bennet, it is generally frowned upon to post the same question in different threads. However I will repeat the same answer I provided in your earlier post:
    I started in the days of manual everything cameras and my habit is to see a subject ( I do street photography) place the central focusing area on that subject, press the release 1/2 way to freeze the focus and exposure for that subject, re-compose and then hit the shutter release.​
    Bennett, what you are describing is not a "manual everything" camera if you can focus by a 1/2 press of the shutter release. Nevertheless, if you maintain the half-press of the shutter it will freeze focus while you re-compose, but only if you have your D810 in AF-S mode. In AF-C mode the camera will attempt to re-focus on the subject under the selected focus point(s) as soon as you press the shutter release. To prevent this you must decouple the shutter release from autofocus:
    To incorporate the AF-ON button into that workflow:
    Set the camera to AF-C mode.
    In the Custom Settings menu set AF Activation to AF-ON ONLY. (This will prevent any press or half-press of the shutter release from initiation autofocus)
    To focus on a subject and then recompose without allowing the camera to refocus: Place focus point over subject then press AF-ON button and hold only until focus is achieved. Then release button, recompose, and press shutter release when ready.
    To focus on a subject and maintain focus on that subject while it moves: Place focus point over subject and press AF-ON button and maintain the button depressed while following subject, until you press the shutter release.
    I seem to be hearing that a camera as sophisticated as the D810 can allow you to set focus on a subject, recompose and then follow that subject if it happens to move.... WOW. How would one set that up with the D810?​
    You would follow the last procedure described above. But you cannot just arbitrarily recompose, hoping the camera will remember the subject on which you initiated focus. You must keep the focus point(s) over the subject (and keep the AF-ON button depressed).
     
  15. Maybe I am missing something, but have never understood why using an AF-on button is better than a half press of the shutter button to activate the AF system.​
    One reason so you can separate focus and exposure. I've never used the AFC function but I use the focus button independent of the shutter button, and then the half-shutter for exposure. When shooting street I usually don't use a dslr, but have many times, more often than not I have the aperture a little more closed down for more DOF, and since things are flowing rather fast sometimes I can lock focus where I want it, choose an exposure and lock that and then recompose, all this in kind of one motion and click. It seems that if you want to use the AFC function, better to compose first and then move your focal point to what you want to focus and then set focus so it can follow. I can see that for continuos rapid fire shooting in sports with a narrow DOF.
     
  16. Focus, metering and shutter release has been separated since the dawn of time and the birth of the camera.
    Having the shutter release, the metering/exposure and autofocus activated by one button is just a newfangled idea.
    I release the shutter with the shutter release button, set the exposure manually with the controls for that and activate autofocus by pressing the AF-On button (always in AF-C, C as in Continuous focus and release priority).
    Using a manual focus lens I do exactly the same except turning the focusing ring instead of pressing AF-On.
    No need to lock anything since everything is locked by default. You can track a moving subject or shoot a static subject or focus and recompose or prefocus and shoot what you want, when you want and how many times you want. No need to change any settings. You're always ready for anything. That's the primary advantage of using AF-On for me.
    I find it very frustrating to shoot with a phone or a compact. It's because the camera is making decisions that I don't agree with. Usually it doesn't focus where I want and it sets the exposure wrong.
    It's the same thing with a camera that has the AF couple to the shutter button, as they all do by default. I can't take a second shot without having to refocus again. Well, you can keep the shutter button half pressed you say. Well, what if I have to change the exposure between shots? What if the camera is on a tripod? What if it takes 30 seconds to the next shot etc etc.
     
  17. Wow, manual focus lenses, when did they invent that? I think some people have never heard of them.
     
  18. I've got myself a new D810 and all these AF intelligent modes are quite new to me. My aim is to shoot pictures of motorcyclists riding their bikes and catching them preferably in frontal 3/4 view coming towards me. They'd be travelling at about a 100km/h or so and am confused as to which AF mode I should use and what the AF lock button does exactly. I've also got my trusty 70-200 f/2.8 and since I live in Malta there would be more than enough natural light at the shoot. Can you help me set my camera?
     

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