🚀 go-pugleaf

In article <9844@sequent.UUCP> brian@crg1.UUCP (Brian Godfrey) writes:
>
>   To sync to a flash you must make sure the shutter is all the way open
>before the flash fires (begins emitting light.) To get reproducible
>exposures you must ensure that the flash is finished firing before the
>shutter closes. (Actually the filaments in flash bulbs glow for a while,
>but that doesn't count.)
> ...
>a switch for "FP" or "X". "FP" is for bulbs (stands for Flash Powder??)
>and "X" is for electronic flash. My old Linhoff (I think it is 1950s
>vintage) has settings on the shutter for "M" and "X" sync. "M" is also 
>for bulbs, though I have no idea what it means. Maybe a loremaster knows

Actually, I recall that "FP" stood for focal plane type bulbs.  M synch
was for standard flashbulbs.  I don't recall the exact heat-up times,
but they were somewhat different for FP & M lamps, so the flash
contact lead times were different.  Type M lamps had a strong peak in
the output.  FP lamps had more of a plateau.  The reason was the M
lamps were for leaf shutter cameras, where the shutter is fully open
during the exposure, except for the rapid lead open/close period.
Thus, a peak would not cause exposure non-uniformity across the film.

Focal plane shutters, when in speeds higher than the X-synch speed
where it is fully open, are actually a slit moving across the film at
a steady speed.  The exposure for these higher speeds is varied by
changing the width of the slit. This is whey, if you use a strobe
flash at a speed higher than the X-synch speed, it cuts of part of the
picture where the slit has not uncovered the film.  For focal plane
shutters to get uniform flash exposures with higher speeds, with the moving
slit, the plateau light output of FP lamps is needed.  The plateau
must be longer than the focal plane travel time.

You don't have to have the shutter stay open until the lamp goes out
to get reproducible results.  As long as the illumination is stable
from lamp to lamp, you can use any shutter speed.  As an example, my
old leaf-shutter camera used M bulbs (the Honeywell capacitor flash
took AG-1's, M-2's, and 25's.)  The most exposure happens of course if
you use the whole illumination curve of the lamp, using shutter
durations of ~ 1/30 sec.  But you could use faster speeds, but you
needed bigger f-stops to get the exposure, since you used only part of
the light.  The table on the back of the AG-1 and M-2 boxes had tables
for shutter speed vs. f-stop.

My Nikon F (circa 1968) has 4 flash synch settings - X, FP, green dot,
and red dot.  The X is strobe flash; no pre-opening lead time. FP was
for FP lamps.  The red and green dots were for M lamps, as I recall,
and were different lead times for the synch closure.  The instruction 
manual had a complex table of lamp type, shutter speed, and synch type.
-- 
David Robins, M.D.  (ophthalmologist / electronics engineer)
The Smith-Kettlewell Institute of Visual Science,  ***  net:  uunet!skivs!dr
2232 Webster St, San Francisco CA 94115            ***  415/561-1705 (voice) 
The opinions expressed herein do not reflect the opinion of the Institute!