I use cheap ND filters from ebay, one of which is much better than the other. A circular 58mm one i use provides natural looking images however, if i took a picture without it, the colour difference of everything is completely different. Another ND filter i've were square, again from ebay, these were pure blue and were horrible.
What I'm asking is, are expensive ND filters free of colour cast and if so have you got any recommendations?
There is no doubt that the cheap ones just aren't worth it. That doesn't mean that you have to spend a fortune for a good ND filter though. I have had both and I tossed the cheap ones because sometimes you just can't get rid of the color cast. I have had really good success with filters from Breakthrough Photography. Again, this all really depends on how much you can afford, if you look hard enough you'll find a good filter at a decent price. I haven't pulled the trigger on square filters yet but I'm looking. I am waiting to see what Irix offers, Breakthrough has a filter holder but it's been on back order for months. I hope this helps.
Thanks for the tips and advice! I had a look at Breakthrough's line, they look extremely good especially with low colour cast. I will most likely get the 3 stop ND, as I normally bracket instead of using grads anyway. Once again thank you!
You'll be happy with that filter.