<<<One is an UV filter to protect the lens in really adverse conditions (leaving it on the lens all the time is bad practise, like playing a violin without removing it from its case), the other would be a polarizer, whose effects would be difficult to simulate in PS afterwards.>>> Per 1) The polarizer is impossible to simulate in PS. 2) The UV filter has me guessing. Are CCD, or for that matter CMOS, sensors particularly sensitive to UV in the same way colour film was? Obviously any overall haze caused by UV cannot be undone later. It's not a simple matter of colour balance 3) For mild colour balance effects the only real reason for using a filter is I guess to reduce the amount of work post capture (remembering to turn auto-colour balance off). For an *extreme* colour cast you are trying to correct there is a lot of sense in correcting it first - presenting the sensor with a balanced mixture of wavelengths. But this extreme is probably beyond anything we meet in outdoor photography. B -- Whatever you Wanadoo: http://www.wanadoo.co.uk/time/ This email has been checked for most known viruses - find out more at: http://www.wanadoo.co.uk/help/id/7098.htm
