[billypip]

Hello everybody, I am seeking a 10 stop ND filter. When I looked at the cost of a quality filter i was astounded so i googled diy nd filter. An article suggested using 2 circular polarizers. Mount the 1st pol on the lens then unscrew the retaining ring on the 2nd filter and reverse the glass, having done this you then mount the 2nd pol on the 1st one and hey-presto..........ND. I took some test shots with it in broad daylight and needed speeds around 30-45 seconds at f8-f11. There is a big problem though.........the shots have a horrible red/magenta colour cast. My original idea was to capture the mood of a cloudy winter sky moving fast so that i could convert to black and white, either in lightroom 2 or NIK silver efex pro. Do you have any step by step instructions on how to remove the colour cast ?

[vonBaloney]

Couldn't you just set a white balance manually with the filter on? And then there would be no cast to remove. (What camera are we talking about?)

[Nass]

Why bother if you're going to convert it to mono anyway?

[vonBaloney]

Actually, if you have lightroom, just move the WB slider until it looks more or less correct. Or if there is a subject in the frame you know to be white (a cloud?), set the WB on that.

[billypip]

thanks for the advice, the camera is an istDL, I will play around with the white balance in my software and Nass........you make a valid point there, thanks.

[newarts]

It is a problem inherent with circular polarizers due to the way the "circular" part works.

It can be avoided using linear polarizers.