>>Steve Parrott wrote: >> >> I know someone here can answer this for me. I will try to explain >> as clear as I can. >> >> I know the "rule" is your shutter speed should be at least the >> reciprocal of your focal length to avoid blur, (assuming no form of >> image stabilization). >> >> I want to use a lens with a max zoom rating of 250 on a digital SLR >> with a crop factor of 1.6, so the 35mm equivalent would be 400mm. >> >> When zoomed all the way out, should I be sure my shutter speed is >> at least 250.... (the lens rating), or 400.... (the 35mm equivalent)? >> >Bob Wise replied: > >Use 1/250 for your rule of thumb. The cropping isn't image >magnification. >
I remark: Use 1/400. Camera shake is based angular displacement. Your hold produces a (presumably) given amount of angular shake. Cropping down a given focal length produces more image displacement, as a fraction of image dimension, for a given amount of angular displacement (i.e., camera shake). The 'crop factor' corrects for this. Ergo, if the minimum speed for a 250mm to avoid shake is 1/250 second for full frame, then it is 1/250 * 1/1.6 = 1/400 sec. for a 1.6 crop. * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
