( ( A teleconverter ) ( ( ( ( has ( a ( convex refraction ) ) ) and ) ( ( can not ) ( ( form ( an image ) ) ( by itself ) ) ) ) ; ) )
(ROOT (S (NP (DT A) (NN teleconverter)) (VP (VP (VBZ has) (NP (DT a) (NN convex) (NN refraction))) (CC and) (VP (MD can) (RB not) (VP (VB form) (NP (DT an) (NN image)) (PP (IN by) (NP (PRP itself)))))) (: ;)))
A teleconverter has a convex refraction and cannot form an image by itself;
(ROOT (S (NP (DT An) (NN image)) (VP (VBZ is) (NP (NP (DT a) (NN copy)) (PP (IN of) (NP (NP (DT an) (NN image)) (VP (VBN formed) (PP (IN by) (NP (NN reflection) (CC or) (NN refraction)))))))) (. .)))