lumelix wrote:

Hi Leonardo
You used a lens with a fixed focal distance, but not with a fixed focus
And if you change the focus while shooting, you also change the nodal point position in the lens!
This results in more distortions over your pano. So don't change the focus.

@ Klaus
For normal stitching, shift or PC-Nikkor lenses aren't nessessary.
But for special use, they are really interesting: If you shift them, you get some images that are shoot exactly in a plane and can be stitched together very precisely.
So you get something like a virtual bigger sensor area by this shifting. Actually PC-Nikkor lenses have a shift about +/– 11mm. So you get a stitched sensor size of 46 x 58mm, or an equivalent of 111 MPixel on a D800 !

No question - i do it also: stitching by SHIFTING.

But we talked about stitching around thge NPP - and here you´ll most likely run into massive problems using a shift-lens because you´re shooting off-axis when you shift.



best, Klaus

Hi Klaus
I think part of the distortion is probably caused by an inexact or moved nodal point and possibly also by a change of focus setting in the upper pano - we don't know so far. When stitching more than 200 such images together with APG, this error will be much more visible.
I only wanted to point out this, in case Leonardo photographed the wall again. Then he can avoid distortions cause by this point
If he don't need the high resolution of a 200mm-pano, shift lenses from Nikon (PC-E) are a good choice, because they have less distortion than other wide lenses and can be shiftet to preserve the vertical lines.
I think a this way created 110 MPixel-image of this wall should be enough for every use. It's a real millimeter-resolution in original size. More resolution will not bring more advantages.
If I had to make this picture, I would try it with a PC-E lens and a higher position. The distortion correction should be made ​​correctly with the Photoshop lens-module.

klausesser wrote:

A NPP-mismatch results in stitch-errors. Not in distortions.

Hi Klaus
Again: I only want to point at this so he can avoid eventually errors when shoot again

A wrong setting for the nodal point will result in paralax errors between the images, and this in stitch errors - I agree.
In this case we have a near flat object, so paralax errors are small and should not result in stitching errors.
But I think, it will also result in global distortions, if you swing the lens upwards and then try to stitch these images together.
It's because the rotation is not around the optical center/nodal point of the system. If the rotation isn't around the NP the POV
will change while rotate, and so the perspective. Any deviation from the optimum condition will cause in errors.

To produce an possible undistorted image/pano a precise setting of the nodal point and fixation of the Focus adjustment is inevitable.
The optimization in APG is also to complex to understand what's going on in detail. It's for stitch images, not for avoid distortions
For the creation of undistorted orthophotos we have a totally other kind of software.

Last edited by lumelix (2013-02-17 13:58:12)

klausesser wrote:

Fine. But he will encounter the very same issue as long as the shooting doesn´t match the very basic optical correlations.

Yes, I totally agree!