A photometer eyepiece utilizing Maxwellian view

This paper deals with the design and use of a small photometer employing Maxwellian view, and capable of being adapted for various purposes. In the first place its development was due to the need for a brightness photometer with a small field of view suitable for polar measurements on diffusing media. By the use of interchangeable lenses and eye-rings, however, its usefulness was widened, and several other applications are mentioned. The theory of the photometer is discussed, and a relation giving the appropriate brightness ranges under different conditions is deduced. The photometer head here described is identical with that used by the author in the determination of the reflection factor of magnesium oxide, in which case its compactness, together with the fact that it can be used on the usual type of photometer bench, led to its adoption.