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PostPosted: Tue May 09, 2006 4:06 am 
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Joined: Thu Jan 26, 2006 3:43 pm
Posts: 217
Location: New York
Looking at the MFT specifications for various lenses, I see that
"in the off-axis field, contrast reproducibility of the lens for sagittal direction
and meridional direction varies with astigmatic affection" -http://nikonimaging.com/global/products/lens/mtf.htm

As a result the MTF values in Sagital direction is higher than MTF values
for Meredional direction (Fine repeating line sets are created parallel to a diagonal
line running from corner to corner of the frame, are called Sagittal lines (S)
and sets of repeating lines vertical to these lines are drawn, called Meridional (M)
line sets. - http://www.sigma-photo.co.jp/english/lens/icon/mtf.htm)

Ultimately, the question I am trying to find the answer to is this:
which stitches would produce less amount of artifacts due to loss of sharpness
of the lens - those which are along the longer side of the frame or the shorter?

Please share our thoughts!:)

Thanks,

Michael Ezra


Last edited by Michael Ezra on Tue May 09, 2006 4:12 am, edited 1 time in total.

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PostPosted: Tue May 09, 2006 9:23 pm 
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Joined: Tue Dec 06, 2005 1:57 pm
Posts: 2946
Location: Grenoble
I would be tempted to avoid using the image corners: the larger the distance between a pixel and the center of the frame (...if, hopefully, it coincides with the lens axis) the lower the image quality. It seems that the damages are not proportional to the distance but rather to the square or the cube of this distance (distortion, CA, vignetting).

Lower quality near the corners is often acceptable for "ordinary" shots, but I'm afraid the truth is for panos, the quality of a lens is as low as the quality of its worst corner ! Using only a square portion of the image make sense (though this could result in lower control points quality.)

Here is another question, regarding very wide-angle lenses versus fisheye for spherical panos (Nikon 12-22 mm, Sigma 10-20 mm rectilinear lenses or Nikon 10.5 mm fisheye): very wide-angle lenses use a large amount of the sensor pixels to record a rather low portion of the sphere (more pixels per angular unit near to the image sides) while fisheye use an equal number of pixels per angular unit (equisolid angle projection for most of them): which one is the best solution?

:) headache ;) headache :) headache ;)

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Georges


Last edited by GURL on Fri May 12, 2006 10:56 am, edited 1 time in total.

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