>A shutter that consistently underexposes by 100% causes the film to receive: > >1 stop underexposure >2 stops of underexposure >3 stops of underexposure >no exposure No exposure of course!!! Nicely placed after the 100% overexposure question to lull the unwary ;o) >A .3 Neutral Density filter transmits what percentage of light incident on Well, 50% is the answer you are after but ... Actually, the real answer is "it depends". - on wavelength(s) - on angle of incidence - on recording medium - polarisation - etc. Perfect ND filters don't exist. Real world ones only give 50% under the precise conditions specified for testing ;o) >The rule of thumb is that to ensure sharp photographs the exposure should >not be longer than: >1/the focal length in mm Shouldn't this be the "effective focal length of the lens ? ;o) (or would that involve going against the tide and teaching the students that digital cameras don't really change the focal length ;o) __________________________________________________________________ INTRODUCTORY OFFER! Tiscali Business Broadband for £15.99! http://www.tiscali-business.co.uk/broadband/?code=ZZ-MS-12KC
