On Fri, January 28, 2011 02:00, Alberto Tirado wrote: >> What can I shoot in the dark that moves at a constant speed >> and is really cheap? >> > > (retort suppressed due to political correctness!) > > >> Or can anyone suggest a set up. >> > > No expert here (stating the obvious!), but I think Andy described in one > of his lectures photographing a turntable with a colored tape (of known > width) on the edge. So, in comparison (due to the short flash duration) I > guess a "guttered" computer hard disk - they have the RPM stated in the > label. Maybe also a household fan. This requires some calculations, but > hey! ;) Putting tape on it will imbalance it enough to be a big deal at 7200 rpm, I strongly suspect. Maybe use a Sharpie marker instead? That still adds mass, but much less, and might not cause a problem in the short term for this use. I suspect a household fan doesn't run at a particularly reliable speed. > Flatbed scanner lamps move at an apparent "constant" speed, but maybe too > slow for this. Some computer fans (at the processor) can be set at known > speeds (via BIOS setup). Good thought on the computer fans. > Another, perhaps more uncomfortable option, would be to put a mark on the > rubber band of a car engine, although this would require more careful > alignment of the camera in a limited space. To determine the running > speed, a first photo at a preset camera speed (with constant light, I > guess) would provide a starting point. Or read it off the tachometer, if your car has one. Don't know how accurate car tachometers actually are. > I have a reputation for finding the hardest way to do something, so I'm > sure there will be more ingenuous solutions. ;) Well, the car engine idea is worthy in this department, anyway :-). -- David Dyer-Bennet, dd-b@xxxxxxxx; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info
