Quote Originally Posted by Dan Fromm View Post
Joseph, optical vignetting (the dread cos^4) afflects all lenses equally. There've been many discussions about when a center filter is necessary. To the extent that there's a consensus, it is that 90 mm is the shortest focal length that can be used on 4x5 without a CF.

When a 90 mm lens is shot straight ahead, i.e., with no movements, the very corners of the 4x5 frame will be 1.5 stops down from the center. Most photographers find this tolerable.

Benno, if this drop of is more than you can tolerate -- it will be if you shoot reversal film -- you should be aware that there are no center filters for the small thin inexpensive 90s you asked about. There are CFs for the modern wasp-waisted ones. To learn more, especially about CFs for lenses whose manufacturers never offered CFs, read my article on the French LF forum. http://www.galerie-photo.com/center-...at-lenses.html
Woah that site has a wealth of information. Thank you! I always found CF really confusing but this is super helpful.