Fine tuning the 180 2.8 on D3

Discussion in 'Lens Lust' started by carauction, Jul 25, 2008.

  1. As I am beginning to shoot a bit more with the D3, I am finding that fine tuning the same fine tuned lenses that I used with the D300, is again necessary.

    I like to shoot my brick pavers at a ballpark distance that I will normally use the lens. I use a strip of colored paper to provide a good subject to focus on wide open(F2.8 here) on tripod. I cut the focus point in half with the strip of paper. A few adjustments places my focus point in the zone. Once I feel that I am in the zone, I then use the lens in my normal field of shooting. After analyzing my real world images, and acutely looking for front or back focusing, I then return to my brick pavers to fine tune if necessary.

    This process seems to work best for me. I fell that using the recommended way of shooting a test chart at 45 degrees, close up and filling the viewfinder with the chart, does not give me real world analysis.

    Here is my D3 and 180/2.8. AF fine tuned at -2 to cure a bit of back focus.

    mike

    click on image for larger view

    _DSC0813.
     
  2. Hi Mike,
    There is nothing wrong with this approach in principle; however, your brick pattern doesn't appear to have strong contrast cracks in both directions which can fool the autofocus and result in an error in AF fine tuning. Your center marker should be of higher contrast I suggest. You could put a few strips of black tape down on the bricks to serve as the area for the autofocus to lock onto. I do like the brick pattern for seeing the defocused regions. Hope this was somewhat helpful.
    Regards,
     
  3. Hi Barry

    Thanks for the reply.

    I don't know if you missed me mentioning that there is a blue strip of paper down on the center of one of the bricks. If you click on the picture, you will see a larger view which shows this. And with the paper in the center of the brick, the focus point is only seeing this paper. You are correct though, the blue paper could use a bit more contrast. But when I focus on it, you can feel the D3 snapping on it like a shark:smile:

    Do you have need to use your AF fine tune much? In particular with the 105DC.

    mike
     
    Last edited by a moderator: Jul 26, 2008
  4. Hi Mike,

    Yes, I saw the blue strip of paper and made the comment you noted. I have found that the autofocus likes to go for contrast and structure having reasonably high spatial frequency, but at times goes not where I wanted while snapping onto what it liked. When I first got the D3 in early February, it fooled me more than I liked to admit when using the single spot focus. :smile: OTOH, the 51-point focus is amazingly good in practice.

    Of the 5 lenses I purchased, my favorite 24-70mm F2.8 suffered front focusing and needed a correction of 18. All the rest were dead on the mark both with near and modestly near high contrast targets. I sent the errant lenses to Nikon Repair in NY and, two weeks later, it came back home all adjusted correctly. Like the others, it was spot on with 0 AF fine tuning. :biggrin: The 105mm DC at first appeared to have front focusing, but careful testing showed it was fine also. It helped me learn more about the behavior of the AF system. I note that when the DC is ON, you need to be careful about the focusing since the DC features introduces selectably under/over-corrected spherical aberration. This shifts where the AF system thinks best focus is located and is dependent upon F/# and where you have the DC control set (although generally you set DC to the same as the F/#, you can set to other values for a different effect). This is an excellent lens, but does take getting use to its behavior.

    Best regards,
     
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