Direct photographic work over a large field (1°) at the prime focus of the classical Canada-France-Hawaii 3·6 m telescope has been achieved with very good image quality (less than 0·5 arcsec FWHM). The basic characteristics of the wide-field corrector (overall image quality, optical lay-out) based on an original design by Wynne are presented. Our Wynne corrector was in fact redesigned to have the last optical surface flat so that a transmission grating could be replicated thereon. There are three interchangeable last elements, those with gratings being wedged in proportion to the dispersion. This arrangement with only three optical elements locates the gratings at a maximum distance from the focal surface resulting in improved resolution over a 1° field, two times larger than that for the five element arrangement at KPNO. The CFH telescope grating-plus-lens, or ‘grens’ has a brightness limit which is fainter than the Palomar Sky Survey.