UNCALIBRATED DISTORTIONS VS UNDERSAMPLING

In a recent paper of ours [Hess & Field (1993). Vision Research, 33, 2 663-2670], we claimed that there was a predictable relationship betwee n position errors and contrast errors for an undersampled system, In t his paper we re-state our main points. We feel that the response to th at paper by Levi and Klein in the accompanying article does not requir e us to produce changes in our original position. We believe that the data support the notion that the principal causes of the positional er rors in the normal periphery and in the amblyopic visual system are du e to uncalibrated distortions in the local signs of visual neurons. We believe that undersampling plays a major role in producing positional errors only in the far periphery at, or very near, the acuity limit. We maintain that our initial studies provide strong evidence that unde rsampling is insufficient as an explanation for the positional errors in the periphery of normals (Hess & Field, 1993) or the central field of amblyopes [Hess & Field (1994). Vision Research, 34, 3397-3406. Cop yright (C) 1996 Elsevier Science Ltd.