I have read that in many cases a Tessar lens has greater contrast due to having less air to glass surfaces than a symmetrical lens. However when perusing through the Schneider website, I have noticed the opposite; that the Xenars have less contrast (from the MTF curves) especially at the edges of the field than the Symmars. Does anyone want to comment as to why this is so? With modern coatings of equal quality, shouldn't the Tessar design have more contrast?

-- John Dorio (john.dorio@ericsson.com), August 31, 1999

Answers

The Tessar design is never quite as sharp in the edges at wider apertures than other designs. Even the newer Schneiders and Rodenstocks of Tessar lineage have the trait. They are great stopped down a couple stops from wide open, however. My Rodenstock one is good after one and one-half stops down. The softer, stretched image in the edges will result in lower contrast ratings for the lens. I love mine, though. It is a low price design which matches anything for landscape or detail work, except when wide open. I don't need to use it that wide anyway.

-- Chris Wray (cpwray@hotmail.com), August 31, 1999.