1 Reply Latest reply on Nov 29, 2010 6:01 AM by MadManChan2000

    request a "fisheye" correction target in ACR

    tksharpless Level 1

      Fisheye lenses are very useful for panoramic photography because they capture a lot of the world in each shot.  They also need a lot of correction for chromatic aberration and vignetting.  And for geometry: there is no standard 'fisheye' projection, each 'fisheye' lens projects the world in its own special way.  To stitch a panorama, the projection has to be known, and be corrected to a standard form so that the s/w can construct a true image of the world.


      Correction with ACR would be an ideal first step in the stitching flow, except for one small problem:  at present it only offers one target for geometry correction,  the rectilinear perspective projection.  That is fine for "de-fishing" moderately wide fisheye images, but far from ideal for preparing stitcher input.  The rectilinear projection may be appropriate for fields of view up to 120 degrees or so, but it stretches the edges of wider fields to an unacceptable degree, and cannot represent a 180 degree field of view at all.


      Most panorama stitching software uses the equal-angle spherical projection (image radius proportional to angle) to represent  the 'ideal' fisheye lens, and corrects the projections of real lenses to match.  That works well in practice even though few fisheye lenses nowadays are designed to the equal angle projection (as many old 'glass footballs' were). 


      Adobe Lens Profile Creator also calibrates fisheye lenses in terms of the equal-angle spherical projection.  So, using Adobe Lens Profiles, it would be easy for Camera Raw to generate corrected fisheye images in that projection.  That would be a great help to panoramic photographers.  Our alignment and stitching flows would be simpler and work better if all input images had a known standard geometry.


      -- Tom