Archived posting to the Leica Users Group, 2003/07/17
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Lee, the M7 curtains moves at the same speed at all exposure times. It is therefore somewhat risky to talk about "speed" or "exposure time" but you know what I mean... The different exposure times/speeds are achieved by varying the (starting) time between the movements of the first and the second curtain. In other words by varying the width of the space between the curtains as they move across the film. The 1/50 second "exposure time" for flash has a good reason: that is the shortest exposure with the whole negative exposed at the same time. Conventional flash goes off when the whole negative is exposed. (Actually the exposure time could have been somewhat shorter, but there is a bit of safety margin built in). For short exposures only a small part (millimetes) of the negative sees light at the same time. If you use conventional flash in that situation, only a small part of the negative, namely that between curtain one and curtain two at the time of flashing, will get exposed by the light from the flash. The setup you describe below solves the problem of partially exposed negatives which result from conventional flash used at shutter speeds shorter than 1/50 second. The solution used is to flash many times at very short intervals during a high speed shutter setting. If the curtain gap is 3 mm, you theoretically need 12 flashes to cover the whole negative by flashed light, I think they use a larger number of flashes with overlapping to be on the safe side. The higher the shutter speed , the narrower the curtain gap and the higher the number of flashes needed. The mind boggles. But Ms are not really for flash, they are for available light and pushed Tri-X or HP5 or -- I say again But Ms are not really for flash, they are for available light and pushed Tri-X or HP5 or -- Chris with apologies for being on topic. >Hi all, > >I tried to figure out M7 sync speed. Here is what B&H >website says: Hot shoe - X-sync at up to 1/50th sec >with TTL (through-the-lens) flash metering capability. >Speeds of up to 1/1000th second available when used >with appropriate Metz flash unit with SCA 3502 >adapter. > >My question is about the latter part of the spec. >Does this mean you can use M7 flash at up to 1/1000th >second when using Metz with SCA3502? > >Thanks. > >Lee > >__________________________________ >Do you Yahoo!? >SBC Yahoo! DSL - Now only $29.95 per month! >http://sbc.yahoo.com >-- >To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html - -- Christer Almqvist D 20255 Hamburg and / or F 50590 Regnéville sur Mer please look at my NEW b+w pictures at: http://www.almqvist.net/chris/dozen/ old pictures still at: http://www.almqvist.net/chris/new - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html