Came across these 2 links which is among the easiest to understand so far on the use of nd filters.
Hope this helps.
Thanks Azurebluee & Clarenze for clearin my doubts.. = )
u wan to try long exposure so that u get those dramtic cloud or water movement right? silky water right? then 10 stops is what most use...
it is easy... before putting on the filter.. check the exposure reading.. and then set to manual mode and add 10 stops to the shutter speed.. use a remote cable if shutter speed > 30s else use your camera own timer... done!
let's take one simple example...
always use iso 100.
iso 100, AV mode, and u meter the scene using whatever metering mode is needed. let's assume the most easily metering mode, the Evaluative.
so, iso 100, AV, evaluate metering, and u set aperture to f8, and camera says 1s is needed. so u switch lens to manual focus and put on 10 stop filter.
set to manual mode from AV and now u only change the shutter speed..
shutter speed is 10 stops more , which is 1s x 2 x 2 x 2 (times 10 2 lah)...
= 1024 seconds = 1024/60 = about 17 min
remember, there is only one change, that is the shutter speed... u need 10 stops more shutter speed bcos ur 10 stop nd is reducing 10 stops of light... -10 + 10 =0..
it's that easy..
Talking about vignetting. If I have a 67mm lens and I step it up to 82mm ND filter. Will there be vignetting? I guess it will occur if I step down; say from a 77mm lens to a 67mm ND filter.