Flash ... at 1/500 seconds
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My 1970 vintage Praktica Super TL made by VEB Pentacon had F and X flash synch sockets. Never did use it with flash bulbs, electronic flash worked well.
"F" connector/setting is something different from "FP".
My sources say to use the M setting for FP bulbs.
Brian though explained that FB bulbs fire faster, thus the synchronisation should be a fit faster (shorter delay than M).
My sources say to use the M setting for FP bulbs.
Brian though explained that FB bulbs fire faster, thus the synchronisation should be a fit faster (shorter delay than M).
Since FP bulb comes up to peak brightness sooner than M bulb, and then it is longer persistent at the peak (to allow use with focal plane slit), using M-sync firing should work fine.if using leaf shutter up to 1/500 or using focal plane shutter at X-sync speed or slower.
The biggest, and unanswered question is "What is the Guide Number that should be used for calculation of exposure aperture?" Very uncertain about accuracy of using a flash meter for electronic flash, with FP bulb in M.
X sync
This is where the bulb manufacturer’s data sheet is important. For example, select “FP shutter” at Thomas link:
https://flashbulbs.com/philips-flashbulb-data/
But that guide number was for feet or meters?
One always has to look for...
Fellows here in this forum say Guide Number and typically mean the feet-one, as most fellows here are "imperial" guys. I myself only use the metrical ones and indicate this by writing GNm.
In manuals it really gets tricky. If it is in English or if sizes are given in inches, the Guide Number will be based on feet. But in general just the value of the Guide Number compared to the size of an electronic flash often tells enough.
Fellows here in this forum say Guide Number and typically mean the feet-one, as most fellows here are "imperial" guys. I myself only use the metrical ones and indicate this by writing GNm.
In manuals it really gets tricky. If it is in English or if sizes are given in inches, the Guide Number will be based on feet. But in general just the value of the Guide Number compared to the size of an electronic flash often tells enough.
Yes... one needs to know; units make a difference! The data sheets I’ve seen/used are always specific and unambiguous about which unit of measurement.
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I have some Sylvania P25B available for sale, mounted on the original cardboard holder, and there is no visible Guide Number data, as the original external packaging is missing. No suggestion of P25B available on the Phillips link either. I have found data sheets on the web, but no Guide Number suggestion...what Guide Number?!
[edit] I finally found a GN datasheet for P25B: for ASA 25, GN = 80 when 1/50 shutter speed. Other shutter speeds have other GN. So ISO 100 has GN160 at 1/50 shutter speed.
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I took a look at the size of those bulbs and probably they are in milimiters. Too big to be in inches. So the guide numbers are probably in meters. Plus if you do calculate the distance, it would be very short if the guidance number would have had been in feet. Thanks to the person who sugested the size thing.
Guidance Numbers in feet is 160 at the those "Sylvania". So at f:8 we have 160 : 8 = 20 feet. That's around 3.3 meters at 100 A.S.A./21 ° D.I.N and 1/50 second exposure time.
Dumping the bulbs, yes, it can be a problem when they are big and you have many an you aren't a home.
@AgX : you say you have 1,000 (one thousand) flash bulbs?
Guidance Numbers in feet is 160 at the those "Sylvania". So at f:8 we have 160 : 8 = 20 feet. That's around 3.3 meters at 100 A.S.A./21 ° D.I.N and 1/50 second exposure time.
Dumping the bulbs, yes, it can be a problem when they are big and you have many an you aren't a home.
@AgX : you say you have 1,000 (one thousand) flash bulbs?
With the size thing I in first instance referred to electronic flashes and their manuals.
But if you got a sketch of a bulb and only a plain guide number it helps too.
I already referred to it, but again. In the 70's the reference film speed incorporated into a guide number changed typically from 18 DIN to 21 DIN. Thus another stepping stone to have in mind when only having got a guide number.
Yes, I got a lot, but no "Texas" ones as indicated.
But if you got a sketch of a bulb and only a plain guide number it helps too.
I already referred to it, but again. In the 70's the reference film speed incorporated into a guide number changed typically from 18 DIN to 21 DIN. Thus another stepping stone to have in mind when only having got a guide number.
Yes, I got a lot, but no "Texas" ones as indicated.
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Older Kodak Master Photoguide has a flash calculator that can provide GN if data sheets not available.
The we have the issue of date of chart for Guide Number, and the fact that ASA values were re-rated (about 1960 IIRC), so then changing what is found in a pre-1960 chart to suit today's ratings.
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If one wants to make a career out of it you could be right. In the past I exposed E6 with flashbulbs using the GN as published on packaging, Kodak Master Photoguide, and a flash slide rule. All came out properly exposed.
The re-rating of DIN and ASA film sensitivity only referred to the films.
Oh, they are middles size.
The only old, german engineering textbook I found that covers this FP matter states that manufacturers of focal-plane shutters, due to manufacturers of flash-lamps typically not spreading output curves for FP-lamps, to offer only one synch-setting for all types of flash-lamps, of 16-18msec pre-run.
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