Camera lenses have been discussed in a large number of books and articles. The approach in this chapter is to concentrate on modern types and to describe imaging performance in detail both in terms of digital applications and in terms of the optical transfer function. By modern types, we mean lens forms that were found on cameras in 1992. The chapter deals almost entirely with lenses for the 35-mm (24 x 36-mm) format. This limitation is unfortunate but not really inappropriate, given the widespread use of this format. Moreover, the different lens types that are described are used for applications ranging from 8-mm video to 6 x 9-cm roll film.
We have not included any specific design examples of lenses for large-format cameras, but the imaging capabilities of these lenses are described in terms of digital applications. By digital applications we mean the comparison of different lens types in terms of total pixels and pixels per unit solid angle. It is hoped that this feature will make comparisons between radically different imaging systems possible and also help to classify lenses in terms of information capability. See "Further Reading" at the end of this chapter for related information about photographic lenses, particularly with respect to older design types.
16.2 IMPOSED DESIGN LIMITATIONS
There are some limitations that are imposed on the design of camera lenses. The most significant ones are listed as follows.
Microprism focusing in single lens reflex cameras (SLRs) is difficult at apertures smaller than about F/4.5. Recent advances permit the use of microprisms at apertures down to F/5.6 and this is usually the smallest maximum aperture permitted in the specification of a lens for the SLR camera.
Depending on the camera type, there is a maximum rear lens opening allowable at the flange on SLR lenses. The limitation is approximately 33 to 36-mm diameter at flange to film plane distances of 40.5 to 46 mm. This affects the maximum possible aperture on