I didn't know where to put this, I figured I'd start here since this area sees traffic that other areas might not see. Someone can move it if there's a better section for it. I'm thinking of an instrument design that has a light path as follows: UV-Vis light source, monochromator or filter that allows only a particular wavelength through, some tubes or whatever, and then the system needs to apply the light to at most the area of a 50mm circle. And, I need a shutter somewhere in that light path, but not an open/closed one. I need one like a camera shutter where I can use a computer or something to tell it to be opened for a specific amount of time so that if I know the output of the lamp in W/m2 I can apply a particular amount of energy per square meter depending on how long the shutter is open. The time it's opened will depend on the source but I'm looking to expose the sample to usually around 0-10J/m2 and possibly more but that's easy, it just stays open longer and usually faster shutter speeds are harder to achieve. I'm having trouble finding such a part, does anyone know of one? This isn't for a spectroscopy application. So basically I need a machine that can precisely and accurately deliver specific amounts of energy to a 50mm diameter circle. I've been using a DNA crosslinker but the lamp stability is dicey if the time the lamps are on is shorter than 30sec, which is pretty much all my exposures.