Recently I discovered a problem with a reddish colour cast when using ND filters for long daytime exposures..

After testing the filter with other cameras and not having any colour cast and also several e-mails and telephone calls to the shop I purchased it from,Pentax, and "Intro 2020" (Pentax and Cokin Distributors), I have finally sorted the problem..

At first we thought it was the a problem white balance, however I tried out every setting on the WB and still got the colour cast. At this stage I gave up and resigned myself to using a polarising filter.

The problem was solved quite simply really and made me feel a bit silly. IF you find you are having a similar problem this is how to remedy it.

In the function menu go to white balance - scroll down to manual adjust - Fit the filter and take a picture of your subject. This will then calibrate your WB solving the problem..