Chuck,
Your explanation and recollection is correct (or at least it matches mine!).
A look at some circa 1960 photography books in your local library will
confirm the variety of light profile versus time variants formerly produced.
Alternatively, anyone can check out the information at this site, especially
if you're dying to actually get photographs with your Olympus' synch
selector in the FP position:
http://www.dhios.demon.co.uk/Flashbulbs/Bulbs1.htm
Nick Smoliga
SvT TF12 - Investment Projects
1103 Avenue B
Arnold AFB, TN 37389-1400
> -----Original Message-----
> From: Chuck Norcutt [SMTP:norcutt@xxxxxxx]
> Sent: Wednesday, May 05, 1999 7:38 AM
> To: Olympus mail list
> Subject: RE: [OM] X/FP?
>
> On: Wed, 5 May 1999 16:18:31
> Mike Higgins <MHiggins@xxxxxxxxxxxxxxxx> wrote
> Subject: RE: [OM] X/FP?
>
> >I know I'm getting way off on a tangent here, but why FP "Focal Plane"
> flash
> >bulbs? What has putting the flash on the focal plane got to do with
> >anything? Surely they would work just as good off the Focal Plane? (I
> love
> >knowing the origins of the markings on my OM-2... and I had assumed that
> FP
> >stood for Flash Bulb, but in another language! in fact I'm sure I've
> told
> >people this! oops.)
>
> Mike
> -------------------------------------------------
>
> I think this is some "ancient" history, Mike. There were earlier
> descriptions of why X and FP sync are different... long rise time of
> bulb vs near instantaneous electronic flash + having to wait until a
> focal plane shutter is completely open.
>
> But, if memory serves me right, the nomenclature "FP" for flash with a
> focal plane shutter pre-dates the invention of electronic flash. As I
> recall there were two different types of flash bulbs. One for use with
> leaf shutter cameras and one for use with focal plane shutters. Between
> flash bulbs the "FP" bulbs had a longer burn time and maybe a slower
> rise time.
>
> With a focal plane shutter the shutter is practically resting on the
> film. To expose the film evenly the shutter needs to be completely open
> during the flash. While it's opening or closing part of the frame is
> obscured.
>
> With a leaf shutter, the shutter is located away from the film and is
> generally in the vicinity of the optical center of the lens (in between
> the elements). Since all parts of a lens contribute to all parts of an
> image, as soon as the shutter starts to open all parts of the frame are
> getting an even exposure. As the shutter opens wider it lets in more
> light but the illumination is still even across the frame no matter how
> much or little the shutter is open.
>
> So, the point of all this is that there were still different timing
> considerations for flash photography even before the invention of
> electronic flash. The bulbs had to be differentiated as to their use
> for focal plane or leaf shutters and the designation hangs on today.
>
> Now, somebody else help me out here if I've got this wrong. As I said,
> it's been a long time.
>
> Chuck Norcutt
>
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