Again with the focusing

Discussion in 'Nikon DX DSLR' started by Beezle, Jul 5, 2005.

  1. I am on my second D2X, the first having been sent in because I was unsure of the focus and a few hot pixels that needed mapping out.

    The tech that adjusted focus damaged the inside of the mirror box, plus did a poor job of calibrating the camera, and I sent it in again. They then overnighted me a new D2X. I was pleased that they went to that much trouble.

    So here I am, some four thousand images later, and I am at the point where I just can't avoid the fact that this camera front focuses just like the original one did.

    Consider the image below. The DOF is over two feet. Pretty wide. But the back end of the focused area is around his sideburns or so. Probably 2.5 inches behind the focused area on his face. It then extends down to just in front of his feet, which are just out of focus. Then back to past my foot, which is perfectly in focus.

    I have a few thousand images with the same exact sort of results. And from a dozen lenses, both AFS and AFD.

    I tell ya, I am not in the mood to send this camera back again. I tried pretty hard to just adapt to the way it is, but I cannot manually focus well enough to put the DOF right where I want it.

    I guess what is bugging me is I have been scanning in hundreds of images I took in 1988 with a Pentax SF-10 camera. You know, back when AF was in its infancy. I used the AF on that camera pretty much all of the time. And every single solitary shot is properly focused.

    Of course the quality of those images isn't quite what we have today in the digital world, but they are okay by and large.

    I think I may give up on this camera. I just can't accept that three attempts on Nikon's part to hand me a five thousand dollar camera that knows how to focus all failed. The $300 pocket camera I carry around can do it. Why can't this camera?

    Anyway, if anyone wants to point out some obvious thing I may be missing, like "yo Ed! it's SUPPOSED TO FOCUS LIKE THAT" I would appreciate it.

    Ed

    [​IMG]
     
  2. jfrancis

    jfrancis

    May 8, 2005
    Orlando, FL
    Hard to say from this shot. A 100% crop would be more useful. You focused on a (relatively) low contrast part of the image. I have found that the D2X requires much higher shutter speeds than my D70, although you are at 3X the focal length now, which should be enough. Finally, did you do any sharpening in post-processing?

    I would try the brick wall or newspaper on a tripod test before you do anything else.
     
  3. I am talking about where the camera focuses, not camera shake or anything similar. The camera's aim. I have shot test images, which showed consistent front focus. This has nothing to do with sharpening or shake or whatehaveyou.

    I thought my description of where the DOF landed was sufficient. I am just wondering if perhaps I do not understand how this camera's AF functions as I saw the same exact behavior from the earlier D2X.

    Anyway, here is a link to the full frame. About 6 MB, JPEG.

    http://www.nvxd.com/forum_source/ben-foster-amphitheater-full.jpg
     
  4. ckdamascus

    ckdamascus

    928
    May 14, 2005
    New Jersey
    It does seem the DoF looks pretty shallow. Are you positive it is 2 feet though? I don't know how to precisely calculate for DoF.

    I don't know how far away you were from the subject which should affect magnification and in turn should also affect the DoF.

    Of course it seems like you have been working with cameras for much longer than me, but I wanted to mention it just in case you forgot. I am almost positive that DoF calculations are different for APS (partial frame) vs full-frame, so if that is the basis of your 2 feet calculation, that is probably why the DoF is shallow.
     
  5. The DOF calculates out to 1.82 feet. While I am not a photographic expert, I have been the lead engineer of software that depended quite a bit on optical geometry, so I have a pretty good understanding of it.

    Look at the image again. My foot, the closest object, is in focus. His ears are not. Now, his feet are just out of focus, but you have to consider the camera's plane is tilted down in relation to him.

    So if you laid a perfectly flat board such that it represented the focused plane, it would lean on his nose with its bottom a few inches in front of his toes.

    I just keep thinking okay, the AF system works the way it works, just adapt to it. But how? I have tried focusing on ears for face on people shots, but that it touchy at best. I have tried tweaking the focus on AFS lenses, but that is unreliable too.

    The camera knows the distance to the subject and everything else it needs to plop the in focus area right where we were taught to put it. I have yet to use a D2X that is capable of this.

    If I lived within a few hundred miles of Torrance, I could probably get this sorted out. If anything, beg to use their tools and fix it my damned self. I wish the mirror stops were as easily adjusted as those on the D70. I would fix it myself. But I don't, and they aren't, and I am weary of the hassle. I just want to take photographs.
     
  6. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    No offense meant as this question comes from someone so new to photography compared to yourself. What are your focus settings? I see that you are AF-Single and single area with the center area selected, but what about the other AF settings?
     
  7. In this case plain old AF-S.

    One thing the Nikon tech person I just talked to said that was new to me - she said focus should be biased 2/3rds to the front.

    Is that so?
     
  8. Here's a neat little program (free) for calculating DOF for 35mm and APS size sensors. http://www.dofmaster.com/

    As for focus on the shot posted, hmmmmmm. Have the same prob (Focus consistency) with my 17-55. DOF and camera shake account for 80% of the error but when everything is in place....WOW!!
     
  9. twig

    twig

    745
    May 23, 2005
    From Luminous Landscape

    " laws of optics is that the DOF extends from 1/3rd in front of the point focused on, to 2/3rds behind it. In other words, you have twice as much DOF behind your point of focus than in front of it."

    I woiuld not trust some random Nikon tech on the phone.
    From looking at your pictures, I would be pissed too. Your foot is clearly in focus and perhaps more in focus than anything in the scene.
     
  10. Well, I would just send it in if I thought I could trust the service folks at Nikon. I don't see the point in sending it in if they are unable to repair the camera.

    Been there, done that.
     
  11. When it comes together, this camera does spit out some nice stuff. An example (about 600K):

    http://www.nvxd.com/forum_source/ben-jun-05.jpg

    But to reiterate, what I am concerned about here is where the DOF lands. After two D2Xs and the same exact behavior on a regular basis, I currently the either this is a 17-55 thing (though I use that lens a lot regardless, so maybe not) or just something about the AF system or I got lucky and happened to have seen two cameras with the same miscalibration.

    The latter should be unlikely.

     
  12. Chris101

    Chris101

    Feb 2, 2005
    Arizona
    There is a chart that you can photograph at a 45 degree angle. You focus on a line and there are numeric scales in front of and behind the focus line.

    I'm not sure where the chart can be obtained, but there is at least one thread here that has information about it and shows some examples.

    Good luck on getting your camera straightened out.
     
  13. I have used that chart and similar tests. They show front focus bias as well.
     
  14. cwilt

    cwilt

    Apr 24, 2005
    Denver, CO
    Beezle,

    For what its worth I am sorry you are having troubles with your D2x. When I purchased mine there were a lot of discussions about D2x focus issues but I went ahead and purchased my D2x. I have not had any issues at all and I hope you do not give up on the camera. As you say it can turn out some amazing images.

    It sounds like you have done focusing tests and I am curious if you tested all of the focus areas? Were they all consistently front focused?


    Kind regards,
     
  15. I have tested about half of them. They seem to be consistent.

    I try not to get lost in fussing over these tests because we can't really say if they are representative and accurate. I try instead to just keep on shooting with these things in mind, and checking the results.

    I can't even say I've had very many images I could consider ruined by such problems. Even the shot above is a good enough memory of that moment.

    But I want a lot out of photography. I am not an artist or even a photographer, but I have a passion for it and I am obviously willing to invest a lot of money and effort in creating the finest images I can.

    And in order to do that, I need some modicum of control over the tools and the medium so that what I end up with is the result of what was in my head.
     
  16. Iliah

    Iliah

    Jan 29, 2005
    nowhere
    It is not always correct. Of practical importance IMHO is that for close distances it is more like 1:1 rather then 1:2.
     
  17. Here are a few "tests"

    I find one of the best subjects for indicating comparative sharpness and focus is half tone printing. You either see the dots or you do not.

    These were shot from an angle about 45 degrees above. So the upper portion of the subject is the foreground. The lower is the background.

    [​IMG]

    [​IMG]

    Just a sanity check before I further bother Nikon about this.
     
  18. jfenton

    jfenton

    Jan 26, 2005
    Haverhill, MA
    Hi Beezle....

    Hmmmm......

    A couple of things?

    A) I'm not convinced that you're going to have sufficient contrast in order for the cameras AF to lock on the tip of the nose / eye plane.

    B) At f 5.6, I think that your actual DOF on a DX format is far less than 2' at this distance.

    C) With the X, the "perceived DOF" is far less than what I'm used to seeing with previous digital bodies because the resolution is so high. Things that used to fall into my understood DOF with my D70 and D2H bodies just don't render the same with the X.

    D) I can fully appreciate the frustrations / concerns that you're feeling as I went through them myself early on. It shoots the heck out of your confidence in your equipment!

    Lastly...I have found that handheld shots (was this handheld?) even at 22mm at 1/60 are incredibly tough with the X. Not only do you succumb to what some are calling "camera shake"....since the DOF is so small here, if your body is wavering at all and the sensor plane moves at all while you take the shot, you are going to see results such as this in my experience.
     
  19. Using a COC for the D2X of .02mm, which I did not come up with, the DOF is nearly two feet.

    Again, look at the photo. My foot is well in focus in the foreground and showing no signs of camera shake. Besides that the camera was mounted as I was planning on shooting fireworks later that evening. Everything in the foreground is lit by the flash anyway, which would make camera shake less likely.

    I have taken plenty (a few thousand?) of other people shots with the focus on their face, eyes, whatever, and their ears not in focus when they should be, yet features in the foreground are.

    At this point I am convinced the camera is the problem.

    How many did you go through before you got settled? I look forward to not thinking about this subject. :)
     
  20. jfenton

    jfenton

    Jan 26, 2005
    Haverhill, MA
    Hi Beezle

    My second one (1st replacement) is a charm :)
     
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