[rollei_list] Re: Flashbulbs

On May 31, 2005, at 6:20 PM, Don Williams wrote:

> At 03:08 PM 5/31/2005, John Jensen you wrote:
>> My vague recollection is that M is 15-20 milliseconds
>> delay, F about 5 milliseconds, and X zero
>> milliseconds.
>>
>> The purpose of the F bulbs was for a short lighting
>> time for action shots (not as quick as an electronic
>> flash, however).
>>
>> John
> Yup, those numbers do sound right when I think back.  Now about 
> everything
> but the M2 bulbs I use underwater is set for X.
>
> My recollection is that what you refer to as "delay" was the delay 
> allowed
> for the bulbs, and would actually be an advance contact trigger time 
> before
> full shutter opening.
>
> What I don't recall is what designation was used for bulbs used for
> focal-plane shutters.  Of course now most focal plane shutters can use 
> just
> about any bulb at 1/30 or 1/60 sec, some even shorter exposures.
>
> DAW
>
> (I'm supposed to be working today but decided to sort of unwind from 
> the
> past few days- I work at home anyhow)

At 1/25 sec., a leaf shutter could open up to all the light from a 
flashbulb and required no delay.  The "M" setting was for flashbulbs at 
shutter speeds higher than 1/25th sec.  It started the filament burning 
a few milliseconds before the shutter opened so the flash could be 
caught at its peak. "F" was for gas filled bulbs that burned a lot 
faster, about 1/200 ms., requiring less shutter delay.

Allen Zak

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