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Thread: E-5 (or E-anything) autofocus accuracy

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    Question E-5 (or E-anything) autofocus accuracy

    Since my early days with autofocus photography (Canon EOS-10s and EOS-1) through my E-1, E-620, and now my E-5, I've always fiddled with AF. It seems that with any camera, I can often press the AF button half way several times on the same spot, and the lens will continue to adjust AF. That tells me that the original attempt was not necessarily spot on. Or does it mean that subsequent attempts are not spot on? This is even true when on a tripod, so camera movement between or during AF attempts is not an issue.

    So, with my E-5 I can very often focus, focus, focus before the lens settles down and doesn't seem to shift any more. I'll bet a beer that most of you can duplicate this behavior. What's going on?
    Regards,

    Jim Pilcher
    Summit County, Colorado, USA

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    Default Re: E-5 (or E-anything) autofocus accuracy

    You mean that after positive focus has been achievied and you want to re-focus on the same spot again, it goes around again only to come back to the same conclusion?

    My thought is that the camera doesn't know it's in best focus possible before attempting small back and front steps to make sure it's in the best possible focus and then settles down.
    Cheers,
    Marin

    E-M5, 7.5mm fisheye, 12mm, 45mm, various flashes and misc.

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    Default Re: E-5 (or E-anything) autofocus accuracy

    Quote Originally Posted by Mar View Post
    You mean that after positive focus has been achievied and you want to re-focus on the same spot again, it goes around again only to come back to the same conclusion?

    My thought is that the camera doesn't know it's in best focus possible before attempting small back and front steps to make sure it's in the best possible focus and then settles down.
    I don't mean that it racks through the focus range again. It only makes a tiny shift with a half-press. Another half-press can make another tiny shift. Typically a third or fourth half-press has no further effect.
    Regards,

    Jim Pilcher
    Summit County, Colorado, USA

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    Default Re: E-5 (or E-anything) autofocus accuracy

    If its worth anything, I did the same thing when focusing with the split prism in the OM days. Just checking to make sure.

    I find the E-5 to be quite stable in focus. The focus point isn't a point, but rather an area, so I find it a non issue unless the end result is OOF.

    Greg

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    Default Re: E-5 (or E-anything) autofocus accuracy

    Quote Originally Posted by fldspringer View Post
    If its worth anything, I did the same thing when focusing with the split prism in the OM days. Just checking to make sure.

    I find the E-5 to be quite stable in focus. The focus point isn't a point, but rather an area, so I find it a non issue unless the end result is OOF.

    Greg
    Greg,
    that hits the point. If the cam's AF runs into the sharp area, it confirms AF, if you press the shutter half for the second time, the AF may run into the same direction to the other border of sharpness, and back and forth. It's a kind of hysteresis of the AF system.

    Mike

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    Default Re: E-5 (or E-anything) autofocus accuracy

    I notice that especially with the 50f2. If I concentrate I can usually tell if it has focus or not visually.

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    Default Re: E-5 (or E-anything) autofocus accuracy

    Quote Originally Posted by James Pilcher View Post
    Since my early days with autofocus photography (Canon EOS-10s and EOS-1) through my E-1, E-620, and now my E-5, I've always fiddled with AF. It seems that with any camera, I can often press the AF button half way several times on the same spot, and the lens will continue to adjust AF. That tells me that the original attempt was not necessarily spot on. Or does it mean that subsequent attempts are not spot on? This is even true when on a tripod, so camera movement between or during AF attempts is not an issue.

    So, with my E-5 I can very often focus, focus, focus before the lens settles down and doesn't seem to shift any more. I'll bet a beer that most of you can duplicate this behavior. What's going on?
    Every time you tell an AF system to set the focus, it makes a check and has to do some calculations, which almost invariably needs to move the lens a little bit even if it a moment later moves it back.

    Remember that AF is just a nice convenience with many limitations in what it can see and how accurate it can be. In some circumstances, it can be more accurate than your eye. In many others, your eye can be far better and has a larger computer driving it to make the "what is in focus" decision.

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    Default Re: E-5 (or E-anything) autofocus accuracy

    I almost always visually confirm the AF with the MF. Of course, I may screw it up as often as not. I'd love to have the split prism on a modern digicam.
    No, I don't miss film...

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    Default Re: E-5 (or E-anything) autofocus accuracy

    I find myself doing this same practice on a frequent basis, reaffirming focus accuracy when shooting in saf/mf and even twitching the focus ring to double check; especially with subjects at a long distance from the lens. 99.9% of the time the camera is right the first time..

    Now in live view that is a different story, I can't for the life of me figure out how that auto-focus system works and usually get results with a distraction near subject in focus while the intended subject falls into bokeh..even after feathering the shutter button several times.
    All that I share with you is purely my personal perspective based on my own experiences. Feel free to constructively criticize my opinions and my photos, please!
    Rob

    E-5/14-35/50-200II/70-300/EC14/EC20/OM100 2.8

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    Default Re: E-5 (or E-anything) autofocus accuracy

    Quote Originally Posted by srf4real View Post
    I find myself doing this same practice on a frequent basis, reaffirming focus accuracy when shooting in saf/mf and even twitching the focus ring to double check; especially with subjects at a long distance from the lens. 99.9% of the time the camera is right the first time..

    Now in live view that is a different story, I can't for the life of me figure out how that auto-focus system works and usually get results with a distraction near subject in focus while the intended subject falls into bokeh..even after feathering the shutter button several times.
    I haven't had so much difficulty with the Live View AF focusing system, but due to the ease of manual focusing in Live View, I usually flip to manual focus when I'm in Live View anyway. Then I use the PDAF override (center point pre-selected) and manual adjust from there.

    One minor difficulty I had with the AF system on the E-5 trying to use S-AF+MF is that I half press the shutter release and dial in the critical focus to get my image in the viewfinder sharp, then adjust the exposure settings (EV compensation usually). In doing so, I almost always release the shutter button from the half-press state, which means that as soon as I press it half way again, the camera refocuses and disturbs my focus settings as I'm trying to frame the image.

    For this reason, I now set the camera to S-AF, half press to focus roughly, then toggle to MF so the focus stays put where I want it and gives me the opportunity to do fine adjustment with no further tweaking from the shutter release button. Or .. just leave it in MF and use the AEL/AFL button to one-shot the AF system.

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    Default Re: E-5 (or E-anything) autofocus accuracy

    My E510 will move focus every time I feather the throttle.
    Most frustrating when you can't see that well to start with. I never know if I'm OOF till I get home, most of the time
    If people don't occasionally walk away from you shaking their heads,
    you're doing something wrong." óJohn Gierach



    Jim
    Visit me at:

    www.hillbilly-photo.com

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    Default Re: E-5 (or E-anything) autofocus accuracy

    I get frustrated with the 50-200mm. When it can't find focus in the distance after trying a millisecond or two, it will search all the way in and all the way out. It really needs a focus lock. Anyway, I think we sometimes expect too much from AF. From the camera's point of view, it is trying to lock on to a target that is jiggling up and down, side to side and to some extent backwards and forwards. To make matters worse, the target is more often than not 3D. With say a face in the distance, should it lock onto the nose, the eyes the ears all of which are jiggling. Too often we expect the AF to simply second guess our own eyes. I'm no expert but I think one becomes more successful at AF by learning its limitations rather than falling for the advertising hype e.g. "...the world's fastest AF".
    E-M1, 12-40mm PRO, 60mm macro, MMF-3
    E-450, 50-200mm SWD, 25mm f2.8, EC-14
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