Cokin Neutral Density Filters will allow you to gain the 1, 2 or 3 apertures you need to allow you to play with backgrounds,
...The Cokin P164 Circular Polariser P-Series filter increases the colour saturation of blue skies, removes unwanted reflections
...Cokin Neutral Density Filters will allow you to gain the 1, 2 or 3 apertures you need to allow you to play with backgrounds, distance & depth of field. This Cokin P154 Neutral Density P-Series ND8x filter will reduce the amount of light reaching the film but without affecting the colour balance. An ND8x Neutral Density P-Series filter has a progressive graduation from the middle to the top of the filter. It is the same colour as the ND4x filter but with a lower tone & will allow a 3 stop shutter speed / aperture decrease. Neutral Density Filters allow you to use the low speeds you need to give an impression of motion.