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Re: Sky and ground issues

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  • panostar
    ... You can manage well enough without control points. Control points enable the optimizer to work out the exact position of each image on the stitching
    Message 1 of 2 , Dec 27, 2009
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      --- In PanoToolsNG@yahoogroups.com, "wirimu2000" <twp@...> wrote:
      >
      > 1, When I shoot out in the open under a clear blue sky I cant seem to work out how to tell PTGui where the control points are for the sky to be attached. How does one get around this?

      You can manage well enough without control points. Control points enable the optimizer to work out the exact position of each image on the stitching sphere, but you probably know the yaw, pitch and roll of the zenith image accurately enough if you are using a panorama head. Pitch and roll are easy: 90 and 0 respectively. Yaw is probably either the same as the last shot in the horizontal row, or 0 if you rotated the head back to the starting position. So first complete optimization with the first shot in the horizontal row anchored at yaw=0, and then enter the y,p,r values for the zenith on the Image Parameters tab.

      Alternatively, use the numerical transform option and apply pitch=90 to rotate the zenith area to the centre of the output area in the Panorama Editor window, and then manually position the zenith image. First set pitch=90 and roll=0 and then rotate the image for the best match. Rotate the entire panorama back to its normal position.

      Depending on the lens used, another option is to tilt the camera down a little for the zenith intead of pointing straight up. In this way, one edge of the shot is lowered into a position where there are features for control points and the zenith hole is still completely covered.

      > 2, I am also having trouble getting a convincing Nadir shot.. especially in confined spaces.. aircraft etc. What tripod coniguration do I use? Software/processing advise ?

      For places where the tripod can be positioned on the floor, take two nadir shots on the panohead, rotating the head through 90 degrees between them. This will give complete, parallax-free coverage of the tripod area and surroundings. Then move the tripod and take a shot of the nadir area, either from the side, or with the tripod tilted over to get the camera more directly in line with the original position. See:

      http://www.rosaurophotography.com/html/technical6.html

      Use PTGui's viewpoint correction to stitch the nadir in. You may need to mask out the tripod and head (and your own body parts)from the nadir shots using alpha channel masks. See:

      http://www.johnhpanos.com/ptgvpt.htm
      http://www.johnhpanos.com/alphatut.htm


      In places where there is no flat floor for the tripod, you need to be more inventive and use alternative mounting arrangements for the panohead: e.g. clamps, pole, monopod etc.

      John
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