Resolution

Take note that this article (like all articles in this chapter) was translated from Russian cine reference book published in 1965. So, we are talking about film only.

Resolution is ability of the lens to register tiny details separately. The resolution is measured in lines per mm that can be distinguished on the negative film. This resolution definition ties a lens properties with some film quality parameters, so it describes rather not the lens alone, but the lens/film system.

For cine and still image lenses this approach provides results most close to real life. Possibility to compare resolution of different lenses is provided by special film types, constant exposures and same developing processes.

Resolution is measured by shooting of transparent test charts with test images in center and at frame field. Special camera is used to provide perfect image plane.

Resolution values in reference books are provided for a fully opened relative aperture of the lens.

The lens resolution depend on energy distribution in the image of point. Thus it serves as a summary of different distortion elimination degree. But it is not same as sharpness or image quality that depends on more factors.

Resolution value drops toward image border usually, that is why it is usually provided for center and for edge (or border). When you stepping the lens down, resolution grows initially to some extent, but then it may drop again.

Modern (as for 1965) cine lenses have resolution of 55-65 lines per mm in center and 25-40 lines per mm at edges.