Philip.

You get two filters with the lens. One is clear and the other is a 4x Neutral Density filter. The one shown loose in the photo below. The clear one is stored in the lens hood. With all the practice I did, I found that with the clear filter, any images with the sky in it were nearly always blown out or over exposed. The photos taken at Old Warden were with the 4x ND filter fitted. According to Sony the filters are part of the lens system and one of them has to be fitted for the lens to work properly.

I actually have both my cameras, the A450 & A550, set with the Saturation at -1 because the colours from the sensor are a bit to bright.

Brian