Hi! I am looking for some advice on exposure. I am shooting 16mm Tri-X reversal, and want to capture dust in the air against a black background. I did a first experiment, and used and exposure meter, and exposed to a grey card, hoping this would most resemble the dust. But the developed film did not come out (basically the black background appears grey, and the dust is invisible). Any advice as to how to expose the film would be greatly appreciated (I am going to try again using different exposures, but any suggested settings would be immensely helpful). I am using two light sources (placement might also make a difference), and also have contrast filters available, if these would help intensify the effect.