The Tiffen filters are supposed to be neutral. They also do one with a slight orange tinge, but a paraglider chappy I know who shoots a lot of aerial stuff uses the haze-1, but says the haze-2a are better. In Lightroom, a yellow/slightly orange filter gives more contrast. I am thinking of trying the UV filter with a yellow grad, but the Tiffen ones cost a fortune.

I just got a reply from Lee filters offering to make me a custom filter, but only in 8 months time when they have the capacity to work on new designs! No mention of price (I imagine it would cost a fortune), I did however offer to field test one for them

I have just replied to them and quoted $500, which seems well below industry rates (thanks for the link, Simon!) No doubt, in the unlikely event they accept my offer, I'll be kicking myself for not asking for more!

I'll keep you all posted! It will be interesting to see if they even reply.

Do you know what helicopter it is? You may be able to open a window. A 17-50 or 18-55 should do it, but take a tele zoom as well. What lenses do you have available?
Try and keep the shutter speed above 1/500th, and stop the lens down to f5.6 or f8. If you can't open the window, try and take along a bit of matte black card to shield reflections, and use a lens hood. On the ground, look where the windows are scratched and try to avoid shooting through the scratches.
Have fun!

I've just ordered a couple of Haze 2A filters, so I hope they work! I had no idea that normal UV filters didn't block much UV.

Intersting, John, so changing the WB will obviously not make any difference. I just found this chart, so I will try the Tiffen Haze-1 filters, which were also recommended by a guy who shoots from a paraglider.

I use a UV filter, but to be honest, it doesn't seem to make any difference at all. I think I will try experimenting with different WB and see if that makes any difference. I know that IR pictures have far less haze, so I will try shifting the WB to the red end of the spectrum and see if that makes any difference, though I would guess the blue light is still reaching the sensor so it might not make any difference once I adjust the WB in PP. I don't have enough technical knowledge to know the answer to that, so I will experiment. I am also going to order a couple of Tiffen haze-1 filters, which apparently stop a lot more UV than the Hoya filters I use at the moment.

It's not so much removing the blue cast (I can do that in PP), it's reducing the light scattering, which occurs more at the blue end of the spectrum, when I take the picture.

Jpegs don't work well at all from high altitude, there's so little dynamic range recorded and far too much processing involved. I have tried them and they just get messed up in processing. As Stefan said, if WB can reduce the effect of a filter, can it then mimic a filter? If so, what colour temp would be worth experimenting with? I would guess towards red? What's the highest colour temp i could realistically use and still get full dynamic range? I might try that, then adjust it afterwards in PP.

Thanks for that tip Stefan, I will give it a try, never came across that before.

John, I don't bother setting the WB at all, I leave it in auto all the time, as the colour temperature is so variable, anything from 4500 to 9500, depending on time of day, amount of haze, amount of water or sky in the shot, and no doubt many other factors too. I shoot in RAW and then set the WB in Lightroom. Often I have to select the further scenery as a heavily feathered seperate layer (or even several layers) and adjust the colour balance, usually adding red and reducing blue, to get the colour looking right. Would it be better to set a mid-range colour temperture on the camera?

Thanks also Graham, I was looking on their site but didn't realise that they had a question and answer section.

This thread was brought about by my incresing frustration at having hundreds (probably thousands) of pictures of amazing scenery, especially in Turkey, Iran, Asia and eastern Europe, and not being able to get rid of the haze and variable blue cast satisfactorily unless it's a particularly clear day, which is not that common. It's also my main motivation for trying infrared.