We've got a new camera in our lab which is less light sensitive than the one we had before, so we don't have to expose the more sensitive one to light which might damage it (though we have not shown that in an experiment ;-)). The determination of the diffusion coefficient with the old, sensitive camera works great! We maybe off by 10%, but after averaging I got close to 1% to the theoretical value.
The new camera is a bit different and less fancy, but our diffusion coefficient is off by a factor of 4 - no matter what we do! It's such a "simple" experiment and I guess it's done as a lab course for freshmen, but it doesn't seem to be that easy. I guess, the camera does some binning and the image info just hides it in a smart way...
