I used to carry about 35 Cokin P filters with adapters every where I went shooting. And 90% of them I never used, so one day I sat down and thought about what I want to shoot and the results I want. I repacked a nice little filter set
– 1x ND8 77mm
– 1x ND Grad 77mm
– 1x Polarising 77mm
And several step up rings to fit all my lenses. I haven’t missed any of the Cokin filters since I did this. Filters do exactly as the name suggests the filter unwanted light.
An ND (Neutral density) filter will simply block a certain amount of light from entering the lens. The amount of light it blocks is dependant in the rating of the filter. The darker the filter the higher the rating, the more light it stops entering the camera
Filter rating F/ reduction
ND 2 1
ND 4 2
ND 8 3
There are filter rated up to ND 1000000 but I personally haven’t seen anything over ND 1000 and would hate to think what an ND 1000000 would cost.
In many situations there is to much light for the photo you want to take e.g. at a waterfall during the day. Even if it isn’t a bright sunny day a normal exposure will be too quick to get “those lovely ghostly white water trails that everyone seems to love”. But by using an ND 8 filter you have just lost 3 stops of light, that combined with a low ISO and stopping my F/ down below 16 my exposure time will increase. And the longer exposure will result in those “those lovely ghostly white water trails that everyone seems to love”
Here you will end up needing a tripod as the exposure time will eventually become way to long to be able to hand hold. Also the quality of the filter my affect the final image.
A set of step-up rings (as pictured above) will allow you to attach filters to lenses with a smaller diameter that the filter. That way you will only need 1 filter for all your lenses, if you get the biggest filter sizes possible. But this my cause vignetting (darkening of the corners) on some lenses.