The Cokin Filter P666 Gradual Fluo Blue 1 is half covered with a blue colour and gently blends into the other half without effect. This is ideal for making the sky and water bluer when capturing landscapes. You decide where in the photo the filter has an effect by shifting the position of the filter in the filter holder. It is also possible to combine two adapter filters with each other. If you combine filters, you can have several colours flow into each other.
Cokin P-Series
You will need an adapter ring and the Cokin Filter Holder BP-400 to attach this filter to your lens.