MTF measurements have recently been carried out in a number of European laboratories on a typical wide-angle photographic lens. While showing smaller differences than those occurring in earlier intercomparisons, the results still exhibited a greater variation than is desirable if the MTF is to be adopted universally in the specification and assessment of lens performance. However, a detailed analysis of the results has indicated probable reasons for many of the differences, and when corrected in accordance with the results of this analysis the spread of MTF values has been greatly reduced, never exceeding ± 0·07 and usually amounting to less than ± 0·03. These residual differences are almost certainly smaller than anything which could be detected as a difference of picture quality.