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Thread: Using the rear AF On button

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    Using the rear AF On button

    I have just bought a 1DmkIV. I am not having good success with BIF shots and am wondering if I have the correct settings / technique.

    I use the rear AF ON button to focus - I just keep the button pressed down, and use the main shutter button to just fire the shutter.

    Is there a preferred combination to use with BIF? ie in cfn iii - 8, what setting would you advise?

    Cheers

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    Moderately Underexposed I @ M's Avatar
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    Fess, I'm not sure how the Canon variation works but I am pretty sure that it is very similar to other brands and having used the "rear button" on Nikon bodies for quite some time now I don't think I could ever go back to using the shutter in combination with the focus function.
    It simply works with a capital W and to me there isn't a single scenario where it can't be used, getting used to it is a short learning process but once familiar with it you will probably feel the same way as myself and many other people.
    Andrew
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    In Training MarkChap's Avatar
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    More so than the rear button, what focus mode are you using, AI Servo will be best for action.
    Also look into the CF's, I am sure you will be able to prioritise when the shutter fires after your initial shot, IE - Achieve focus priority, Frame rate priority etc. My 7D is very customisable in that area, so i would expect the MkIV to be just as customisable
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    Quote Originally Posted by fess67 View Post
    .... I am not having good success with BIF shots and am wondering if I have the correct settings / technique......
    I'm not sure what this CFN III - 8 setting is supposed to alter, but I'll have a quick sqizz to see what it is.....


    .... Kind'a doesn't make sense to me(never seen it, in person, never tried it)

    But what may help in some way is; Use a single point only .. you would pre choose this point before you attempt to shoot the scene.

    Keeping focus mode as Mark said in continuous tracking mode(servo mode), you hold the AF-On button down to maintain focusing ability on the subject at a point on the subject already determined.
    Try to maintain a steady hand and panning motion as you track the bird as the camera/lens tries it's best to hold the best possible focus.
    Smaller aperture lenses will obviously have a harder time of focusing or maintaining a focus hold than will a faster lens.
    That is a 400/2.8 will obviously (or should!) acquire and hold focus better than a 500/4 which in turn will focus better than a 400/5.6 .. and so on.

    From what I read on the camera's cfn system, I'd look into cfn iii - 2 which adjust the sensitivity of the focus tracking system.

    More sensitive means that the camera will search for focus with a quicker refresh rate, whereas lower sensitivity would stop the camera from trying to acquire a new focus point.
    if you are slightly unstready as you track the bird, and the focus point is not held at the same point on the bird(eg eye, or beak, or whatever) and the focus point is constantly changing, then you want to slow down the rate of change of the focus tracking system so that it doesn't hunt around as it sees different elements to focus on.

    Hope that makes sense, and I hope I have the system's terminology the right way round too!

    With the equivalent Nikon system for focus tracking, they call it 'delay', where you can set it to short or long.. ie. sensitive or less sensitive.

    What the delay actually means, is that if the focus point originally acquired changes slightly, for a brief moment, the delay in trying to find a better focus distance, is adjusted(either quickly or slowly).

    The other day I was trying to track a micro sized birdy in amongst a cluttered tree canopy. The mess of twigs and branches and leaves had the lens focus hunting, even tho I sometimes had the bird in focus.
    As it skittered around the insides of the tree canopy, I kept losing focus as the camera quickly switched from bird to branch to leaf, to bird.

    there is no perfect setting, but there is a decent balance to work with.

    The other cfn item I noticed of interest was cfn iii - 4.
    If you have the camera set to servo mode focusing, I would set this menu item to continuous tracking priority if it isn't already.
    It may slow down initial focus acquisition time by an amount, but it will also make it a priority to hold focus once it's been achieved as it tracks the subject.


    Of course technique is vital in this overall equation.

    I'm normally quite good at focus tracking, most subject material(that I've been exposed too on a regular basis) but this birding caper has got me beat!!

    How these regular birding guys do it on a regular basis, has me ....
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    I'm with you arthurking83, a local outing with AP birding guys was quite sobering and heightened my already significant respect for the bird crowd.

    @Andrew (I @ M), I hope you enjoy your Nikon variation of Back-Button AF, a Canon invention!

    fess67, I agree with other posters, it is not likely back-button AF is critical to your results here. More critical to use Servo AF, play with the sensitivity of AF, and (my tip) use a suitable zone AF rather than spot AF for actual in-flight shots.

    But it still won't guarantee results: these guys are skillful!

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    Moderately Underexposed I @ M's Avatar
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    Quote Originally Posted by Arg View Post
    @Andrew (I @ M), I hope you enjoy your Nikon variation of Back-Button AF, a Canon invention!
    Well there ya go, never knew it was invented by canon. One learns something everyday eh.

    Question is though, when Canon put it there, why didn't they make it actually work so that it achieved focus -----

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    Thanks guys,

    Thank you Arthurking83...that is the sort of info I wsa after. I studied the book last night and made some changes but I went the other way with the speed at which the camera hunts for focus. 2 minutes after getting home from work I realise I should have gone the other way. Will get out there and play some more over the next few weeks.

    Thanks again all

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    Here, read this:

    http://cpn.canon-europe.com/content/...m_functions.do

    It explains a little better than the manual. You still need to find what suits you best though. I can't help as I have the Mk III and don't do BIF anyway. There's a custom function that allows you to give priority to attaining focus with the first shot and then gives priority to tracking for subsequent shots in a burst. There are 62 custom functions available.

    You might want to check that sensitivity setting you were discussing. I think you'll find it is sometimes better to set it slower to stop the camera from swapping to another subject. That is what they say in the link I gave you and that seems to be the case for me when shooting a moving subject over a busy background. (See page 9)

    CFIII-8 might also be of assistance to you.
    Last edited by camerasnoop; 17-04-2012 at 8:22pm.

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    I am assuming BIF = Bird in Flight?

    If that's the case, I found the following help (I have a MKIII)

    It doesn't really matter if you use back focus button or not for bird photos, but I personally LOVE the back focus button and will not go back.

    1) Slowest sensitivity possible on AF tracking (so if another bird get into the frame it wouldn't get "distracted")
    2) Shutter speed at least 1/1000 at f/8. You are using MkIV so you can set to Auto ISO. I am using a MkIII so ISO 800 and above works the best for me
    3) Use Spot metering - and metering at selected AF spot
    4) Depends on the size of the bird - With bigger (or closer in some case) you can rely on center point only. But with smaller one, you need to employ more AF points
    5) use AI Servo, but I guess you know that already
    6) A good panning technique... personally I found monopod really helps in certain (but not all) situations.
    7) Focus early, allow at least a second for the AF Servo to "predict" what to do next
    8) A lot and a lot of practice. Out of 200 pics I get 1 or probably 2 that I really like, and sharp.
    Last edited by andylo; 17-04-2012 at 8:36pm.

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    Quote Originally Posted by I @ M View Post
    Well there ya go, never knew it was invented by canon. One learns something everyday eh.

    Question is though, when Canon put it there, why didn't they make it actually work so that it achieved focus -----
    I guess they got lazy -- it only had to be better than Nikon!

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    Thanks for all the replies guys.

    Have tried several tweaks / changes and some limited successes. Beginning to doubt the camera at the moment as even static shots are hit and miss. Will post another thread on this later.

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    I use the AF-ON button the opposite way it's meant to be used. I assign it as a AF-off button. This allows me to use autofocus most of the time with the half shutter and when in low light situations and the AF is starting to hunt, i'll hold it to disable the AF and manually focus. I don't know if it's applicable to Birding cause i don't have any real experience in that genre.

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    A royal pain in the bum! arthurking83's Avatar
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    Quote Originally Posted by KeeFy View Post
    I use the AF-ON button the opposite way it's meant to be used. I assign it as a AF-off button. This allows me to use autofocus most of the time with the half shutter and when in low light situations and the AF is starting to hunt, i'll hold it to disable the AF and manually focus. I don't know if it's applicable to Birding cause i don't have any real experience in that genre.
    That kind of makes sense in specific situations, but the problem is that having the shutter half pressed all the time like this will drain battery a lot quicker.
    It makes sense in a situation where you are shooting a lot, but if you are simply scanning the field looking for the opportunity for a shot and then activate focus when needed, battery will last longer.

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    Quote Originally Posted by fess67 View Post
    Thanks for all the replies guys.

    Have tried several tweaks / changes and some limited successes. Beginning to doubt the camera at the moment as even static shots are hit and miss. Will post another thread on this later.
    Static shots? Well it's time for basic testing. Put the camera on a tripod and shoot something flat. Try live view vs viewfinder. Check micro focus. etc.

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    Quote Originally Posted by Arg View Post
    Static shots? Well it's time for basic testing. Put the camera on a tripod and shoot something flat. Try live view vs viewfinder. Check micro focus. etc.
    Yeah thanks for that. I am hoping to get some time tonight to do some testing with the 1DIV and 5D2 with the same lenses.

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    Still in the Circle of Confusion Cage's Avatar
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    Quote Originally Posted by Arg;1008962@Andrew (I @ M), I hope you enjoy your [I
    Nikon variation[/I] of Back-Button AF, a Canon invention! :
    Well I don't really care who invented it, but it's on my K5, and I'm using it, and loving it.

    I admire the results the BIF folk post, see Shelley's 2011 Pic of the Year, and I'm sure a lot are achieved hand-held, but for us mere mortals, particularly those in my group, the chronologically challenged, a Gimbal type head may be a help.
    Cheers
    Kev

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    Don't doubt the AF of the 1D4
    These are my settings. They may not be suited for you but you could giver them a go and tweak to suit your own preferences.

    C.Fn III: 1 Autofocus/Drive USM lens electronic MF - 0
    C.Fn III: 2 Autofocus/Drive AI Servo tracking sensitivity - one click to the right of "Slow"
    C.Fn III: 3 Autofocus/Drive AI Servo 1st/2nd img priority - 0
    C.Fn III: 4 Autofocus/Drive AI Servo AF tracking mode - 1
    C.Fn III: 5 Autofocus/Drive Lens drive when AF impossible - 0
    C.Fn III: 6 Autofocus/Drive Lens AF stop button - 4
    C.Fn III: 7 Autofocus/Drive AF Microadjustment - 2
    C.Fn III: 8 Autofocus/Drive expansion w/selected pt - 0 But if your shooting BIF you might like to change it to - 2 i.e Surrounding AF points
    C.Fn III: 9 Autofocus/Drive Multi-controller while meter - 0
    C.Fn III: 10 Autofocus/Drive Selectable AF point - 0
    C.Fn III: 11 Autofocus/Drive Switch to registered AF point - 0
    C.Fn III: 12 Autofocus/Drive AF point auto selection - 0
    C.Fn III: 13 Autofocus/Drive AF point display during focus - 0
    C.Fn III: 14 Autofocus/Drive AF point brightness - 0
    C.Fn III: 15 Autofocus/Drive AF-assist beam firing - 0
    C.Fn III: 16 Autofocus/Drive Orientation linked AF point - 0
    C.Fn III: 17 Autofocus/Drive Mirror lockup - 0
    C.Fn III: 18 Autofocus/Drive Continuous shooting speed - -
    C.Fn III: 19 Autofocus/Drive Limit continuous shot count - -

    C.Fn IV: 1 Operations/Others Shutter button/AF-ON butting - 2. This IMO is the best setting for bird photography. Infinitely better than using the shutter button for both focus acquisition and actuating the shutter. It gives you much more control I believe.

    I only use AI Servo even on static subjects. But as you know most of the time the birds are twitching around and Single Shot would yield OOF birdies.
    I always shoot at maximum fps. Even perched birds can quickly change from a boring sitting/standing pose to a dynamic wings-up beak open pre or post flight pose
    It took me a little while to become comfortable and competent with my 1D4. Be patient and practice practice practice!!!!!!

    Just my thoughts.... hope it helps a little

    Chase those birds
    Chris

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    Member James02's Avatar
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    My own experience with shooting birds on a 7d is
    1. If you are shooting small fast birds in the open where it is difficult to keep them in the viewfinder at all then you want a faster focus change.
    2. If you are shooting birds who can fly behind things, branches etc then you want a slower focus change.
    So I use either fast end of the scale or middle depending on the need.

    James

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    can't remember Tannin's Avatar
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    Quote Originally Posted by arthurking83 View Post
    [Reverse back button focus] kind of makes sense in specific situations, but the problem is that having the shutter half pressed all the time like this will drain battery a lot quicker.
    Huh? How is this different to using the AF any other way? (Ans: it isn't.) In any case, battery life on a 1 Series camera is not an issue - these things have massive great batteries that last for days and days.

    Quote Originally Posted by KeeFy View Post
    I use the AF-ON button the opposite way it's meant to be used. I assign it as a AF-off button. .... I don't know if it's applicable to Birding cause i don't have any real experience in that genre.
    The camera was designed to have the AF-ON button programmable. It is not "meant to be used" in any particular one of the three main ways it can be used and was designed to be used, it is meant to be used in the way that works best. (And that way will be different for different people.) Me, I am the same as you: I use reverse back-button focus, and I reckon it's perfect for birding, especially birds in flight. (Though ordinary shutter-button focus is fine for flight shots too.)

    To the OP: I suspect that your back-button focus method is not helping you with flight shots. It has to slow you down a bit, that clumsy reach with your thumb for the AF button while you are already busy with other stuff. Well, maybe you can get used to it, but you are asking your body to do a complicated thing in a situation where a simple thing will do - and with flight shots, every micro-second counts. But if you use BBF for all your other work, maybe the confusion of switching to a different method just for BIF would be worse than just sticking to what you are doing now.

    As for your camera settings, if in doubt, use the factory defaults. The 1 Series cameras have superb focus abilities right out of the box and although they are extensively customisable, most changes you can make will degrade rather than improve the already excellent focus response. I used a Mark III for many years with great satisfaction, and now a Mark IV, and I am still in awe of how good the AF on these cameras is. It doesn't get any better than a Mark IV, which is one thing I really like about using one - if I'm not getting the results I want, I know I am already using the best equipment there is, so it can only be my own fault: I have to try harder and work smarter.
    Tony

    People say nothing is impossible, but I do nothing every day.

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    Thanks for the responses.

    I still have issues with the number of keepers being pretty low. I see many shots in a burst that are soft or very OOF. I am sure you are right and that it is a technique issue and it is one I am trying to figure out as I use the rear focus button on the other cameras with no problems. that said I am not really birding with them.

    I think I need to pick bigger, slower targets to start, gain confidence in the machine rather than keep doubting it, and then move onto the harder craft of getting good shots of birds.

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