A very good question. I have used medium format for years (6x6) without giveing this much thought. I don't know the answer, but AFAIK the speed "rule fo thumb" is connected to the magnification factor - or distance to subject. Anyway - a 100mm enlarges the picture twice (135 film)- thus twice the speed. If you can hold 1/60 sec. steady enough for a 50mm - you must use at least 1/125 sec. for a 100mm. For MF it should be tha same. Perhaps you can hold a 75 mm standard lens steady enough at 1/60 - then a 150mm will require 1/125 sec. If the camera movement, that gives you acceptable unsharpness on the film with a 75mm will result in similar accaptable unsharpness using 1/125 sec. at 150mm.
I don,t know anything about shock absorbtion - except that the movement caused by chock (mirror/shutter) seemingly results in similar calculations as for camera movements caused by shaking the hands, while taking the picture. All the best Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt -----Oprindelig meddelelse----- Fra: Andre Langevin [mailto:[EMAIL PROTECTED] Sendt: 22. juni 2004 00:11 Til: [EMAIL PROTECTED] Emne: Medium format "speed limit" and shock absorbers... I am about to use a Pentax 645 for the first time during a trip next month. I will bring 45mm, 75mm and 150mm lenses (and maybe a 200mm if I find a cheap one before leaving). I would like to know if the medium format "speed limit" is the same as with a 35mm SLR: if 1/60 is fine with a normal 50mm lens, does the 645 need a faster speed when used with its normal 75mm lens? Is the mirror well "shock absorbed" on the (original) 645 as with, say, the MX? Andre
