Assertion: lens's element | /r/HasAspect | short focal length
Facets:
value: very
type: DEGREE
value: grouping behind it
type: LOCATION
Source sentences:
text: This problem is resolved by constructing the lens as an inverted telephoto, or retrofocus with the front element having a very short focal length, often with a highly exaggerated convex front surface and behind it a strongly negative lens grouping that extends the cone of focused rays so that they can be brought to focus at a reasonable distance.