To all concerned:
I want to take a minute to clarify some things that are being said here on this thread.
There seems to be a concern over the way that different manufacturers of projection screens are measuring their gain properties. For those who may not know, a block of Magnesium Carbonate is used as the base white material for all gain measurements in the screen industry. To my knowledge, our friends at Stewart are using the same type of measuring devices and base material that we use at Da-Lite. Therefore, the claim that was listed above, to my knowledge is not true and as many statements on this forum, should be taken with a grain of "salt". Perhaps the reason for the statement is the fact that as stated in their literature, Stewart uses a material by the name of PTFE as a reference material for color reflectivity. However, I am doubtful that that is the material used for gain measurements. Perhaps that is a question to ask them directly.
If you want to verify what a particular screen manufacturer is using to determine the gain of their screens, simply ask them. Either through the forum (which I now Don Stewart is a member) or by calling them directly.
I felt obligated to address this situation, since Da-Lite was mentioned in the above posts.
Blake Brubaker, CTS
Vice President of Sales
Da-Lite Screen Company, Inc.