You are right about the influence of the support. If the Questar is the lens then the Questar "tripod" is much sturdier and vibration free than most any standard light tripod. As for the mirror dropping ... I meant that when the exposure is made the mirror is up regardless but in live view it is up all the time while in standard mode the mirror needs to flip up before exposure. This is probably the most problematic facrtor in terms of introducing vibraton. But I think you and I are on the same wavelength so to speak. Andy On Jun 8, 2012, at 10:43 AM, Roger Eichhorn wrote: > Perhaps attach an accelerometer to the camera body? But, wouldn't the sturdiness of the tripod and the presence of externally induced vibrations be the determining factors? > > What fraction of the incoming light is allowed to pass through the mirror to the "film" plane? > > Roger
