None Plasmat Objective for Large-Format Photography J. Brian Caldwell This month’s design is a plasmat type, which is the most common type of lens used in large format. Log in or become a member to view the full text of this article. This article may be available for purchase via the search at Optica Publishing Group. Optica Members get the full text of Optics & Photonics News, plus a variety of other member benefits. Publish Date: 01 May 2000 Add a Comment Please enable JavaScript to view the comments powered by Disqus.