flashbulb question for rolleiflex

[BrianShaw]

More on guide numbers. Unless a table of guide numbers based on film and shutter speed is specified on the bulb packaging, as SiriusG earlier mentioned, the generic guide numbers are technically for1/25 to 1/30 shutter speeds. The Kodak recommended corrections for higher shutter speeds are: plus 1/2 stop for 1/60; plus 1 stop for 1/125; plus 2 stops at 1/250. Source: page 13 of 1966 Kodak Master Photoguide. I find these corrections essential when shooting slides but less so when shooting film with more latitude.

Those corrections were fore clear bulbs. For blue bulbs there were similar corrections on page 12, with a 1 stop correction at 1/60 and 1.5 stop at 1/125.

 

[Jim Jones]

Some shutters, Ilex for example, had non-X setting for F bulbs. Graphex shutter has 2 M settings (black and red) but I'd need to do homework to recall the difference.

According to the 11th edition of Graphic Graflex Photography by Morgan & Morgan, the red M setting provides about 9 or 10ms delay. Delay for the black M setting is not clearly stated, but implied to be about 19ms.

 

[Sirius Glass]

The package of bulbs should give guide numbers for different size reflectors and their surfaces based on the shutter speed.

 

[mjork]

One more detail: the guide numbers on the package were computed for indoor use. They assume some light bouncing off the walls and ceiling. For outdoor use or in large halls, you loose one stop of light. So in those circumstances, just use the GN for half your actual film speed.

This is documented in some of the old GE or Sylvania flashbulb brochures. And some packages also say so. I've also verified this myself by measuring the flashbulb light output outdoors with a Sekonic flash/light meter: I'm measuring almost exactly one stop less than indicated by the GN on the package.

 

[Arklatexian]

No, M is the type of synchronization and is not related to magnesium.

I am sorry if I caused a misunderstanding by mentioning magnesium wire in the flashbulbs but there was another flashbulb manufactured that required a different delay. That was the type "F" bulb. Some older synched shutters had a switch that read: "X", "F", and "M". The Rollei shown only had "X" and "M". You, of course, are right. The "M" does not refer to the magnesium wire in the bulb before it is fired......Regards!

 

[Sirius Glass]

I am sorry if I caused a misunderstanding by mentioning magnesium wire in the flashbulbs but there was another flashbulb manufactured that required a different delay. That was the type "F" bulb. Some older synched shutters had a switch that read: "X", "F", and "M". The Rollei shown only had "X" and "M". You, of course, are right. The "M" does not refer to the magnesium wire in the bulb before it is fired......Regards!

Relax, we are not in school any longer so we are allowed to make mistakes. For example once I was married. I corrected that.