The PDF on this web site contains corrections made after the original
publication. The document in the SPIE digital library does not contain
these corrections.

2008-Sep-30

* Fixed Moon & Spencer's formula again. This time should be correct. 

2008-Aug-20

* Fixed Moon & Spencer's formula (typo in latex formula). Thanks
to Kenichiro Masaoka.

2008-Jun-30

* Fixed reference to Moon & Spencer's formula (was wrong in Wyszecki & Stiles)
* Fixed Figure 2 (Optical MTF plot). Plot used different formula than the formula in the paper.