sentences:  Attaining maximum lens speed requires engineering tradeoffs, and as such, "prime" (fixed focal length) lenses are generally faster than zoom lenses, and modern manual-focus lenses are generally faster than their autofocus counterparts.With 35mm cameras, the fastest lenses are typically in the "normal lens" range near 50mm and there are several high-quality fast lenses available that are relatively inexpensive.For example, the Canon EF 50mm 1.8 II or Nikon AF Nikkor 50mm 1.8D are very inexpensive, but quite fast and optically well-regarded.