Archived posting to the Leica Users Group, 2000/11/17
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Tina et al., Thanks for doing the filter test. Your hand-held Minolta meter indicates 3/10ths, or in other words, almost 1/3 of an f stop light loss from your UV filter. Exactly which UV filter were you using? I am still at a loss for why your readings are different. Maybe it has to do with the fact that in a predominantly warmly lit (tungsten/yellow/blue deficient) environment, the meter reacts differently to the reduction of the ultra violet rays than if the meter was presented with 5000K daylight. I don't believe there will be any evidence of light loss on the film itself, especially not 1/3rd of a stop. If you exposed a gray scale, or Macbeth Color Checker, at the same exposure, with and without the UV filter, I am doubtful there would be any visible or measurable difference. Also, I believe, as other members have said, the UV filter does NOT have a greater effect if the light level is very low in the environment you are shooting in. The transmission qualities of the filter are fixed, and it will always let all light rays below a certain wavelength pass through it, no matter what the intensity level of the light source is. Maybe this is just a color temperature issue, where the meter's sensitivity is erroneously effected by the reduction of UV, but the actual film itself is not. Someone needs to do an actual transparency film test and measure the results with a densitometer. Sorry I don't have the time to do it. Regards, Rob McElroy idag@pce.net Tina Manley wrote: > At 11:43 AM 11/17/00 +0000, you wrote: > > >An aside to Tina: What instrument do you use to measure darkness? ;-) > >Nick. > > O.K., Nick. I tried it again. I am using a Minolta IV F Auto Meter. I've > entered 3200 as the ISO and 1/125 as the time. In room light, without the > UV filter in front of the meter I get an f number of 2.89. With the UV > filter, I get an f number of 2.86. Not much difference, it's true, but > enough to matter when you are taking pictures in the dark! In my dark > hallway, with an ISO of 3200 and 1/30, I get a reading of 1.0 without the > filter and a reading of "under" with the UV filter. > > Tina > > Tina Manley, ASMP > http://www.tinamanley.com