This Schneider-Kreuznach Center-Filter is a specialized filter designed for use with large format wide angle lenses. This filter has a 1.5 stop neutral density effect in the centre, with a radial clearing to the edges: effectively, it darkens the centre of the image to bring its exposure closer to the edge exposure, reducing the effect of vignetting. The Center-Filter is designed for use with 90mm lenses (this one is designated for the 90mm f8 in particular) but it may be usable on other lenses with a 67mm front thread. In excellent condition, with original leather case.