AF-On button

Discussion in 'Nikon' started by steve_may|1, Sep 27, 2009.

  1. Hi everybody
    I use a Nikon D300 for nature photography, including birds in flight, and I'm curious - why do people use the AF-On button to autofocus. So far I've just used the shutter release button with continuous focus and been reasonably happy with the results. From what research I've done I've found 'professional' photographers seem to use the AF-On button to focus....clearly this is just heresay though. Nikon are quite intelligent about the ergonomics of their cameras so I feel I am missing out on something....can't have that!
     
  2. The idea behind the AF-ON button is that when you have activated the custom setting that turns off autofocus from the shutter button you have separate control over exposure timing and focusing. If you have an AF-S lens, then you can activate autofocus from AF-ON, follow focus (in AF-C mode) by pressing and holding it, let go of it and turn the manual focus ring if that's what you want (no switches), and when you actually want to take a picture you can just do that without autofocus kicking in without you specifically asking for it to focus. When you take spot meter readings it's nice that it doesn't rack the focus around while you're doing that. But others prefer autofocus to be activated from the shutter button. I don't really understand why ...
     
  3. Nikon recommend using the AF-On button for sports photography...
    They have a good PDF download explaining how "Guide to professional sports photography" on there website.
     
  4. Thenks for the replies to date, can you provide a link to this PDF download Anthony as I can't track it down.
     
  5. It is a matter of personal choice, there is no particular advantage of decoupling release from AF function for BIF since you want AF at all times. I almost never use it since I find working with one button easier than holding one and pressing another.
     
  6. I use the AF-On button exclusively. It becomes second nature after about a day of shooting. I think it allows me to have more control over focus in fast situations. I can hit the AF-On button, focus, and then take my finger off of the shutter button and the camera is still focused at the distance I want it at. I can recompose and move to a different angle if I choose and I don't have to concentrate on holding the shutter button "half-way" down.
     
  7. ShunCheung

    ShunCheung Moderator

    If you shoot birds in flight, you should half press on the shutter release button to get the camera to maintain focus with your fast-moving subject and then when the composition is right, press the shutter release all the way to capture the image at the timing you choose. At least to me, it does not make any sense to use a separate AF-ON button to initiate focusing for any type of action photography.
    I also have a Contax 645 and with that camera, I use its AF-ON equivalent button to focus. I used the Contax 645 for static subjects only and there you want to effectively lock focus and then fine tune your composition. Additionally, the Contax 645 has only 1 AF point so that AF and recompose is a must with it (if you use AF at all).
     
  8. I like to have a separate AF-ON button b/c during AF tracking, it is difficult for me to maintain just the right amount of pressure on the shutter release. When I press it a little too hard, it triggers the shutter, very annoying.
     
  9. ShunCheung

    ShunCheung Moderator

    CC Chang, we are shooting digital now. If you accidentally trigger the shutter and end up with frames you don't want, just delete them later on along with the many other bad frames. You won't be wasting any film any more.
     
  10. If you shoot in a multi-frame mode, the auto focus tends to hunt between frames, even with continuous-servo focus. For sports and nature action shots, using the AF-ON button rather than the shutter release makes this manageable. For most situations, using the shutter release to engage auto focus works best, with the AE/AF-L button programmed appropriately.
     
  11. I switched and I'll never go back. My wife was skeptical, but ended up switching after trying it for a few days. It really does simplify things once you get used to it. It prevents you from accidentally refocusing when using focus/recompose method as well as (as others have said) preventing you from putting too much pressure on that hair trigger when focusing continuously and taking the shot before you are ready. I think it is nice to have the shutter release button ONLY do one job . The only situation where AF-ON is tricky is when you are holding a heavy camera/lens combo in vertical orientation (without a battery grip) with one hand (which is not really a very good idea anyway). My camera is almost always setup Cont. servo, single focus point, spot meter, Manual mode, AF On only. It basically renders the C,S,M servo button useless (especially if your lenses have the AF/M focus ring). I'm certainly not knocking people who don't use it, but it's a very useful technique for me.
     
  12. Suppose you have one of the simpler cameras without the 10-pin remote control. You do have the little ML-L3 remote however. The camera is on a tripod and you want to focus and recompose. You have two options - use manual focus or use AF-on. You have to do this because the camera will normally focus as soon as you press the button on the remote control.
    With AF-on you point the camera where you want and press AF-on once. Then you reframe the picture and release the shutter with the remote control.
     
  13. I've tried the AF-on method and really see no advantage unless you use 'focus and recompose' which the shutter release half press AF obviously can't do. Focus and recompose is inaccurate and no longer required with the good focus tracking of the higher end nikon cameras, it really just seems to come down to a choice of whether you find holding a button or the half press more comfortable.
     
  14. I can see a benefit using the AF-On button for landscapes when I'm using my tripod as I have been focussing for max depth of field, switching the autofocus off and recomposing.
    However, for fast action photography this doesn't apply to me. A couple of people have suggested that the focussing 'hunts' between frames whilst using the shutter release button to focus, implying that this 'hunting' doesn't go on if one uses the AF-On button only for focussing. Is this true, does the camera 'hunt' more (ie more soft shots) between frames when using the shutter button to focus and release? I'd certainly appreciate any comments here.
     
  15. I use the AF-On button for focusing, not the shutter button. It just seems right. But after reading all the above posts I couldn't understand why. I needed to think about this. The counter arguments are convincing. Rather use the focus points which are more accurate. Of course the the D3 doesn't have enough focus points in the portrait orientation, but that's another issue. So why does it feel wrong to me to have the shutter button determine focus? My conclusion is that it gives you more control to have focus on a dedicated button. Perhaps it's because the majority of my photography has been done with manual focus cameras, ie cameras with no more than 3 controls: aperture, shutter and focus. It's nice to focus when you want to rather than because you have to every time you press the shutter. So I think it's more philosophical than practical. But it's certainly not impractical. If you're focusing on a bird in flight it's no quicker to use the shutter button than to keep the AF-On button depressed.
     
  16. At least to me, it does not make any sense to use a separate AF-ON button to initiate focusing for any type of action photography.​
    I use the AF-ON button for action (rodeo, racing, etc) 99% of the time. It is just much easier to hold the AF-ON down to track then to click the shutter when I want a shot. It also eliminates any accidental shutter clicks. Plus, when I'm tracking a moving target, its not like my thumb is doing anything else anyways, even if I need to reach the command dial, its not far away.

    Personally it works better for me. That doesn't mean it works for other people.
    CC Chang, we are shooting digital now.​
    My F100 (which I use alongside my Digital) has an AF-ON button. Its easier to get in one habbit than two seperate habbits for digital and film. With digital, its not as much as a money issue as a time issue.
     
  17. Here is how I use the AF-ON button on my Canon 5D Mark II.
    1. When shooting at night I use Live view to zoom in 100% magnify and manually dial focus in very exact. However, with L-series lenses I don't have to switch lens to manual mode I just over ride by turning focusing ring. If I forget to move the auto focus off shutter button when I go to take the final picture the camera will try to refocus again (auto focus adjust). This messes up my finely tuned manaul focus and I have to start over. By moving this to the AF-ON button it eliminates this problem.
    2. The second situation this becomes a problem is in very low light situations where the camera is hunting. If I know all the action is 3 -6 feet I will focus 1 time to something in that range and not refocus again at every shot. Otherwise, I stand to miss shots because camera is hunting. I would rather just take a slightly out of focus photo than miss an exiting moment.
    3. Focusing when camera is wide open using an 50 or 85 1.2L where the focusing plane is very narrow. I want to zoom in and spot focus on what is really important to me in the shot. Then I zoom out to get the composition I want but not refocus on new items that may now be in the frame. I then want to take multiple photos with out the point of focus changing after each press of the shutter button.
    These are just a few examples of why I like to move the AF off the shutter button.
    However, when I am just shooting casually not studio work I prefer the AF and shutter button to be combined in one button. Then I don't forget to hit the AF-ON button and can just take the shot.
     
  18. Seems everybody has his/her prefence then. So far, I'm very used to half-pressing the shutter, so the AF-On button does not get a lot of work. But I see the advantages for sports photography - but even then, habits are hard to loose, so once used to half-press button.... I'm glad at least the D300 gives the choice to do things multiple ways without doing them more right or wrong than others :)
     
  19. Thanks for the responses, very informative. One concern that grew was 'does the autofocus work better in burst mode when the AF-On button is used as opposed to the shutter release to autofocus?'
    I phoned Nikon technical support and asked them this question directly yesterday, and happily, they said they both provide the same level of autofocus accuracy.
     
  20. I couldn't use the AF-On, if you have small hands, the buttons are alittle too far apart, atleast on my D200 they are.
     

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