R.Gould
Member
I have 2 srt 101's from the 60's that have FP socket's, FP sockets are only found on camerasas using focal plane shutters and are for special slow burn flash bulbs that were designed to maintain a constant light while the shutter slit traversed the film you can also get F sockets or snc that are meant for special high speed flash bulbs which will start to fire approx 5 miliseconds before the shutter reaches peak opening M sync was for the medium speed elictric flash bulbs, which are now obsolete class M flash bulbs have a firing delay of 18 to 22 miliseconds so M was designed to fire the flash 20 milisewconds before the shutter reaches full opening, and was used mainly with leaf shutters, and is not normally an extra socket, althoiugh IO have cameras with an extra M socket, and some with only M socket, and X sync is for electronic flash and fires the flash at the moment of full shutter opening, so you can find older cameras that use focal plane shutters with F,FP and X sync sockets, but the usual is X and FP, but rarely if ever with M sync, whichb is normaly on the older folders and cameras with leaf shutters, and thwey all serve a diffetrent purposeWell, I looked through dozens of textbooks on flash lighting and camera design from several countries. Not even a hint at a FP contact.
As said I see it as M-contact in disguise.