D300 missing focus

Discussion in 'Nikon DX DSLR' started by PhilDPho, Aug 2, 2008.

  1. I noticed this a few days ago with my 1 month old D300.

    It will occasionally miss focus. I shot a wedding yesterday and it became clear it was a problem and not a user error. On more testing today, none of my lenses are mis-focusing a test chart. However, if I add another object near the focus point I'm using, even on single point AF and single servo, the AF picks it up, causing what I had selected for focus to be out of focus.

    I noticed this in the church yesterday, when photographing the bride and groom the D300 would pick up focus on guests behind.

    Or it would pick up focus of the altar, etc.

    Has anybody had any similar problems? Or have any idea how long a problem like this would take to fix as I would ideally need it back for 6th September for another wedding.
     
  2. fivegrand

    fivegrand Guest

    Mine only does that in group focus mode when the primary focus points picks something up with greater contrast than what you want the focus point to be.

    I don't think it's a "problem or issue" as much as it's just something to get used to (all of my previous AF cameras did this too).

    Edit: A thought - the actual focus sensor may be larger than is presented by the viewfinder bracket. That may explain why your object "near the focus point" in single point mode is catching attention. *totally a shot from the hip not based in anything factual
     
  3. That's what it seems like to me, but it's not really acceptable when using single point, single servo AF. For it to be picking up and focussing on something on the other side of the frame.

    After doing some more tests, I find I can manually focus, more accurately than the AF.

    I've never had an AF body mis-focus before, never mind like the D300 is doing. My fiancee's D60 doesn't do it, my D80 didn't do it, my D40 doesn't do it. The D100 and D200 doesn't do it.
     
  4. fivegrand

    fivegrand Guest

    Well, which is it focusing on? On the other side of the frame, or near the focus point? It's changed from post to post :) 
     
  5. I'm experiencing both. Focussing on the other side of the frame irregularly. But I can recreate it misfocussing near the focus point regularly with a test chart and my lens cap.

    I tried focussing on a light stand with a 1/4" thread on it, shot at 55mm where the threawd filled the AF point and 2.8 the image is soft, I get a better result manually focussing.

    Aswell as the problem with the AF missing and focussing elsewhere. I've also once or twice had it miss completely, and the subject has been OOF and the there was nothing else in the foreground.

    I'll post some examples up once NX2 has finished a batch process.
     
  6. fivegrand

    fivegrand Guest

    Hmm, yeah that's not so good. The light stand thread *could* be attributed to the shiny and irrregular surface throwing it off a bit, but other than that - got me stumped (which doesn't take much).

    It does seem like an issue. Have you consulted with your closest dealer? I have never had this issue dealt with by a repair center (lots of shutters replaced) and obviously in the US not in the UK.

    I haven't had this issue arise with mine - perhaps yours just needs a little tweak from the factory. Everybody on the assembly line has a bad day once in a while...

    Edit: Have you double-checked your "closest subject priority" settings?
     
  7. I've sent an email to Nikon Support, and will give them a call on Monday. Hopefully I can get it in asap and it'll be a straight forward fix.
     
  8. This is why I was hesitant to go the D700 route, because I'm not sure if it's the D3 AF. The D300 is fast to focus, but lacks precision focusing such as the D2X and D3. The D300 has AF limitations in two areas: low contrast subjects and subjects with very little background separation. They even note these AF limitations on the D300 manual. The D300 is great, but it ain't no pro body with pro AF!
     
  9. I can understand the D300 isn't as accurate with AF as a D3, however. I do expect it to be significantly better than a D40, D60, D80 and a D100.
     
  10. Now, I am not sure what settings you have when you say you have problems with the AF, but if a4, that is the same on the D300 and D3, is set on anything but off, there will be a hesitation of the AF to reacquire focus on a new subject or set of subjects. This I believe is mostly when using AF-C, but might apply in AF-S. I had to get used to the D300 AF, when I first got it, but now find it VERY good!! Now this image was made with the D300, AF-C using 51-point and it definitely has a busy foreground and background.

    0_0_1efd72424b2a36eb4e25589ac743fcfe_1.



    Nancy
     
  11. Interesting I turned a4 off, and after a few tests it seems to be quicker and more accurate. Although I need to do a few more tests to see if this has solved my in-accurate problem
     
  12. jmark

    jmark

    142
    Feb 6, 2007
    Greer, SC
    a4 is ?
     
  13. a4 is focus lock on. If you have it set to long, when you have a subject in focus and something passes between you and the subject it will not immediately refocus to that object. The settings short, normal or long is just the time set to which it will not refocus. You do not have a manual??

    Nancy
     
  14. jmark

    jmark

    142
    Feb 6, 2007
    Greer, SC
    ^ I have a manual just not with me.
     
  15. So will having a4 turned off, will this cause any issues with tracking?
     
  16. It depends on what you are tracking and in what environment you are tracking it in. If turned off and something get in the way of the primary subject focus will refocus to that new subject right away instead of hesitating that few seconds.

    nancy
     
  17. so I assume if I'm shooting portraits/weddings or anything where there's no obstructions I'm better with it off. And turning it on for sports such as hockey and football or birds?
     
  18. Yes, I would try that.

    Nancy
     

  19. AF is much better with my D700 than with my D300 for what I shoot. I noticed it right away and started thinking my D300 is *broken*. But after testing on high contrast targets, it's fine. It's the low contrast/dark light stuff that causes issues.
     

  20. I do not have any issues that way. The low contrast/dark light stuff is a lot of what I shoot. This shot was with my Nikon 500 f4 with the 1.4TC right before a thunderstorm, so light was not very good, iso 1250 and I had not problems focusing. And as you can see both have busy surrounds. My a1 setting was on Focus, and I was using AF-C.

    0_0_783a8dc8c4676100f8a83b823f9afbc6_1.

    This also was in not so great light and very quickly taken for he flew off not seconds after I shoot this.

    View attachment 232975

    Both are crops, NOT full frame. I love my D300!! It just took practice getting used to it.

    Nancy
     
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