The Cokin P060 Centre Spot P-Series Filter consists of a gray outer area, the spot outside of the image centre will be reproduced less sharp than the centre. The effect of the centre spot filter is directly influenced by the f-stop & the focal length. The transformation is softer with wider apertures. The size of the clear circular area increases relatively with the selection of longer focal lengths. The exposure determination should be done without the filter. If the camera has the capability of spot-metering, then you can measure with the filter in place. This filter measures 85 x 85mm & fits the Cokin P series holder.