Patrick Barry Posted March 12, 2010 Share Posted March 12, 2010 Ok, so here goes a pretty dumb sounding question that I will ask anyway. If I pop an ND4 filter onto my lens, and the exposure would normally be an 11, do I count that stop (the 11) as one of the 4 stops down? If that makes sense? Would it be a 4 or a 2.8. Thanks guys!! Link to comment Share on other sites More sharing options...
Brian Drysdale Posted March 12, 2010 Share Posted March 12, 2010 It actually reduces by 2 stops, the 4 refers to a 1/4, so at f11 you'd open to f5.6 with the filter on. This explains the method used for defining ND filters. http://www.cs.mtu.edu/~shene/DigiCam/User-.../filter-ND.html Link to comment Share on other sites More sharing options...
Premium Member David Mullen ASC Posted March 12, 2010 Premium Member Share Posted March 12, 2010 Ok, so here goes a pretty dumb sounding question that I will ask anyway. If I pop an ND4 filter onto my lens, and the exposure would normally be an 11, do I count that stop (the 11) as one of the 4 stops down? If that makes sense? Would it be a 4 or a 2.8. Thanks guys!! I don't know why, but the still camera filter market is now using "ND4" to mean a 2-stop ND and "ND8" to mean a 3-stop ND -- I guess because a filter factor of 4 is 2-stops and a filter factor of 8 is 3-stops. In cine terms, a 2-stop ND would be an ND.60 and a 3-stop ND would be an ND.90. So an ND4 filter would mean you'd have to open from f/11 to f/5.6 to compensate. Link to comment Share on other sites More sharing options...
Eric H Posted March 12, 2010 Share Posted March 12, 2010 I don't know why, but the still camera filter market is now using "ND4" to mean a 2-stop ND and "ND8" to mean a 3-stop ND -- I guess because a filter factor of 4 is 2-stops and a filter factor of 8 is 3-stops. In cine terms, a 2-stop ND would be an ND.60 and a 3-stop ND would be an ND.90. So an ND4 filter would mean you'd have to open from f/11 to f/5.6 to compensate. someone, somewhere is going to get a nasty surprise one morning in telecine......my suggestion to anyone who's not sure, is to run your spot meter thru anything that might require compensation...if you don't have a spot meter then use your still camera and watch the number of stop loss the meter says when you put your filter in front. If you use the camera method be sure to use a uniformly lit object, like the sky or the white cyc/limbo in a studio, or a grey card. good luck, Eric Link to comment Share on other sites More sharing options...
Patrick Barry Posted March 23, 2010 Author Share Posted March 23, 2010 Thanks all! That certainly explains a lot! :) Link to comment Share on other sites More sharing options...
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