Tile joints in nadir images (align edges)

[strarsis]

Hi,

When stitching tile joints in nadir images with the rest of the panorama, the tile joints often don't completely align.

One reason can be that images from the Sigma Fisheye lens (and probably other Fisheye lenses) have the tendency to become blurrier towards the edges.

The sharper tile joints of the nadir images look more different than the blurrier tile joints towards the edge in the rest of the panorama, hence PTGui has issues with aligning them correctly, even with lots of control points between those tile joints and 'Very good' optimization result.

Currently I have to retouche those tile joints in Photoshop, but the misalignment makes it cumbersome.

Can an extra Control Point type be introduced in PTGui that helps to align edges, not just tile joints, but also other structures like ceiling trusses, drop ceiling tiles, etc.?

Thanks and with best regards

[John Houghton]

The edges of the tiles should align well if you have control points on the surface of the tiles or edges.  However, the gaps can look very different when viewed from different directions, as happens when shooting a viewpoint nadir with the camera significantly offset from the original position.  It helps if you lean the tripod over to minimise the offset distance.

It's true that you can have mismatches due to the differences in image quality between the sharp nadir and the unsharp edges of the images surrounding the nadir hole.  You can address this by either (1) shooting a pair of nadir images with the tripod still in position and the camera pointing directly down, panning round through 90 degrees between them, or (2) tilting the camera down for the lower row so that the edges are not used.  Another option that some people have used is to deliberately degrade the nadir image quality to make it match the unsharp image edges!

John