Tim Jackson's Focus Test Chart (http://md.co.za/d70)

Discussion in 'Nikon DX DSLR' started by Saratoga Lefty, Apr 23, 2005.

  1. I have been having on and off problems with focusing. Yesterday afternoon I used the Focus Test Chart created by Tim Jackson (http://md.co.za/d70) and tested the nine cross sensor reticles on my D2X each separately. I didn't bother with the two outlying reticles but may go back and check those as well. Following Tim's detailed instructions I concluded that I only have problems with some of the reticles. Most of my shooting thus far has been at apertures of F8 and beyond which can hide the front and back focus problems if they are very subtle. Tim's test is done wide open. I used my 28-70 2.8 locked down on the Arca Swiss Ball Head mounted on my Gitzo 1325 with the SB800 Flash attached. Further, I used the self timer to avoid any camera shake. Per Tim's instructions only tested with AF-S and Single Area and focused on his test sheet from fairly close using each of the nine cross reticles separately resulting in nine Nef photos which could then be examined at 100% in Capture. My findings were:

    Upper Left Reticle: Slight front focus with Capture indicated focus point slightly lower
    Upper Center Reticle: Front Focus with Capture indicated focus point slightly lower
    Upper Right: Slight Front Focus with Capture indicated focus point lower
    Center Left: Focus Excellent with Capture indicated focus point very slightly lower
    Center Center: Focus Excellent with Capture indicated point very slightly lower
    Center Right: Focus Fair with Capture indicated focus point right on
    Lower Left: Focus Excellent with Capture Right on
    Lower Center: Focus Poor Back Focus with Capture focus point right on
    Lower Right: Focus Poor Back Focus with Capture focus point right on


    These results in AF-S help explain to me why when I use Dynamic Area Focus on fast moving small objects (e.g. birds) my shots are hit and miss. It all depends upon which reticle is in play for a given shot. I did get better results in Group Dynamic but still not what I expected and if I limit my shooting to the center reticle all seems fine, but why should I have to do that? I'm waiting to hear back from Nikon Service to see if I should send it in.

    I recommend you try the focus test yourself on each of your nine individual cross sensor reticles to see what kind of results you get. It may surprise you and if you've mostly been shooting at smaller apertures (e.g. F8, F11, etc.) then you probably wouldn't even have noticed it. I'm certainly not trying to start any trouble but I do think we ought to get what we paid for and not always have to wonder if the shot will come out as expected.
     
  2. jfenton

    jfenton

    Jan 26, 2005
    Haverhill, MA
    Hi Bernie

    I think that what you're seeing is the inconsitency for the actual focus point to be on the areas indicated in the viewfinder. It's pretty typical that they don't match up and I believe Thom Hogan and others have actually mapped them for certauin cameras in the past.

    I know that with my D2H, the only reticule that was really dead on for what I saw in the viewfinder was the center one.

    I don't know if this is the cause for the issues with the X or not. I would assume that all of the cameras are not quite what you see in the viewfinder, but this wouldn't explain why there are some cameras that appear to be focusing correctly...unless of course they are aligned better.

    My guess is that these issues may have existed in previous cameras, but the increased resolution of the X is what's allowing us to see these issues crop up.

    Interestingly, you noted that if you used the center reticule on your x that it seemed to be dead on on actual shooting conditions. With mine, I absoluetly could get front focus on one shot and back focus on the next. I never really found any of them to be perfect...except when manually focusing.
     
  3. Jim,
    Not only did I see the inconsistency for the focus points to match up in Capture with where I was actually aiming, I also had two reticles with Poor focusing everywhere, one with only Fair focus, and three with Front Focus. I think this test shows the problem clearly and it is very similar to a test Ron recommended to Tom Marshall today on the DP review Forum only Ron suggested using sticks in the sand and a tape measure. Testing each individual reticle seems appropriate. I took some photos today at the Giants Vs. Brewers game and only used the Center Reticle and for the most part the majority of my shots were in focus. Large subjects compared to birds and only used center reticle.
     
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