NNP sensitivity?

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  1. NNP sensitivity?

    #1

    Hi all, I'm a new pano head user (bought myself an NN5 for Xmas). I've been trying it out a little, but I haven't been real successful calibrating it. I get the concept, but the execution is where I get stuck. I thought I had pretty good settings for my walking around zoom at "normal" focal length (i.e. 50mm @ 35mm equiv), so I tried making a 3-row pano in my living room. It came out quite well... way, way better than any indoor pano I've ever shot without a pano head... but still there are minor stitching errors that I'm having trouble eliminating by choice of control points.

    My question today is, does anyone have a feel for how sensitive the settings of the NN5 are for a given zoom length? For instance, if I have A = 50 and B = 85 for 50mm focal length, but because of error in repeatability, the zoom lens is actually at 49mm or 48mm, will A and B settings on the pano head need to change significantly, will they generally still work, or is it totally dependent on lens design (e.g. some lenses can be super-sensitive to small changes while others seem to have a wide sweet spot)?

    Is there any general feel for how far off the settings can be before you start getting stitching errors you can't fix? I ask that because I'm wondering whether I should be expecting to find my fix by changing my settings +/- 5mm, or more like +/- 0.5mm.

    Thanks,
    Rodney

  2. Re: NNP sensitivity?

    #2
    Users Country Flag
    Join Date: Apr 2008
    Location: Saddleworth UK
    Posts: 242

    If you have followed John Hortons Or other traditional methods to find your NNP it should be very accurate.

    The more likely cause of errors are in poorly chosen control points. Or lack of experience with, or suitability of your chosen software.
  3. Re: NNP sensitivity?

    #3
    Users Country Flag
    Join Date: Apr 2008
    Location: Hong Kong
    Posts: 2,364

    Quote Originally Posted by icysubdweller View Post

    My question today is, does anyone have a feel for how sensitive the settings of the NN5 are for a given zoom length? For instance, if I have A = 50 and B = 85 for 50mm focal length, but because of error in repeatability, the zoom lens is actually at 49mm or 48mm, will A and B settings on the pano head need to change significantly, will they generally still work, or is it totally dependent on lens design (e.g. some lenses can be super-sensitive to small changes while others seem to have a wide sweet spot)?
    it depends on how much the lens barrel moves. How many mm does it move?


    Nick



    Fanotec
    We listen. We try harder.
  4. Re: NNP sensitivity?

    #4
    Users Country Flag
    Join Date: Aug 2008
    Location: Netherlands
    Posts: 1,733

    When i set my zoom lens, i always turn from low to high and stop in the middle of the numbers of my nikkor lenses. Then i tape it before starting to shoot. I accidentally , without tape, moved the zoom just outside one number during changing the pitch.

    I had stitching errors in verticals. I think this is dependent of the construction of the lens an how much the elements move. You can mark the zoom setting with a tiny little white spot on the lens to reproduce the position. Having done that you can find the NPP and you are steady with your setting.

    Btw., you do not have to change the lower rail setting. Only upper rail settings change when you zoom in and out. To find an exact zoom position, you can use the exif data to find out where you are: 46, 48, 53 or exact 50.


    Heinz
  5. Re: NNP sensitivity?

    #5

    If you are using PTGui, it may be that the optimiztion parameters are not adequate. In advanced mode, select the Optimizer tab. If using Simple mode there, select Heavy + Lens Shift in the Minimize Lens Distortion field. If using the Advanced panel, check lens parameters a,b,c,d,e.

    If that doesn't solve the problem, check for horizontal and vertical parallax by including something close to the camera (50cm) in horizontal and vertical overlap areas. Make sure that there is suitable detail in the background so that any parallax shift can be assessed in a layered PSD output by switching layers on and off.

    John
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