[rollei_list] Re: Flashbulbs

----- Original Message ----- 
From: "Don Williams" <dwilli10@xxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Tuesday, May 31, 2005 3:01 PM
Subject: [rollei_list] Re: Flashbulbs


> At 12:16 PM 5/31/2005, Richard wrote:
>>   The GE No.50 and Sylvania No.3 were meant to be used in
>>studio reflectors with very slow shutter speeds (1/25th or
>>longer) or open flash. A single bulb in a 12" reflector 
>>has
>>a guide number of 600 for ISO-100 film. Thats f/6 at 100
>>feet folks, try that with your stobe units. Remember, 
>>these
>>are bulbs about the size of 150 Watt household lamp.
> Was that the purpose of the "M" flash setting.  I had 
> cameras which had "F"
> and "M" flash settings.
>
> It seems to me that the "F" wasn't related to focal plane 
> shutters but I'm
> not sure.  I think it was another flashbulb setting.
>
> I had to grind a new cam to change the "F" setting on an 
> old Argus to make
> it "X", which was for strobes.
>
> Anyone have any recollection about this?
>
>
>
> Don Williams
> La Jolla, CA
>
   There were 4 classes of bulbs made:
Class F, for Fast. These were miniature gas filled lamps 
requiring a 5 millisecond delay. They could be used with 
unsynchronized shutters at slow speeds.
Class M, for Medium. The majority of flash bulbs fell into 
this class. M bulbs require a 20 to 25 ms delay.
Class S, for Slow. These included the No.50. They required a 
longer delay than 25ms and were usually used with open flash 
or very slow shutter speeds (more than 1/25th sec.).
Class FP, for Focal Plane. These bulbs required around a 
15ms to 20ms delay and  were made so that the maximum output 
had a broad relatively flat peak lasting around 40ms. The 
output increased a little during the peak to compensate for 
the acceleration of simple FP shutters such as the one in 
Speed Graphic and Graflex cameras. 35mm cameras could be 
used at a variety of speeds but 4x5 Speed Graphics and 
Graflex cameras were limited to the 1/1000th sec speed where 
the total travel time of the slit was short enough.
   Newer miniature lamps, flash cubes, etc., may not fit any 
of these catagories.
   FWIW, flashbulbs were introduced about 1931 by Wabash. 
Wabash was eventually bought by Sylvania. General Electric 
was the other major maker of flash bulbs although there were 
other brands from time to time. Early lamps had crumpled 
aluminum foil in them. In later bulbs the foil was replaced 
with wire or fine ribbon of aluminum or magnesium or an 
alloy. The nature of the foil or ribbon determined the shape 
of the light output curve. Class F, gas filled lamps, also 
called Speed Midgets, were developed around the late 1930's 
mainly for use in inexpensive cameras since they could be 
used with a simple flash contact. The duration of the flash 
was very short, perhaps equivalent to a shutter speed of 
1/200th second so they provided some motion stopping ability 
to box and other simple cameras.
   I've used lots of flash bulbs over the years. One of my 
memories is of the frying noise and burning plastic odor of 
the plastic coating and the crunch of bulbs under foot. 
Nasty messy things they were but fun to use.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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