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Re: [OM] Flashbulbs

Subject: Re: [OM] Flashbulbs
From: "John A. Lind" <jlind@xxxxxxxxxxxx>
Date: Sun, 04 Aug 2002 03:22:40 -0500
At 02:20 8/4/02, Chris Barker wrote:
Dear all

With my newly acquired OM4Ti (Mint in box!) I received a flashbulb holder for the hot shoe. It is called an Olympus Flash CL. However, Shipman says that only the OM1N can be used with Photo Flash.

Does anyone have any experience of using Flash Bulbs (the ones I have are Type 1B) and if the GN calcs on the pack are reliable? If I get no replies I shall have to do some tests...

You made me dredge out the Kodak Master Photoguide, circa 1978!
What is the shape of the reflector?  This determines guide number.

AG-1B guide numbers for ISO 100, in feet, and X-sync at 1/30th:
  Polished bowl and hi-power flash cube:  130
  Shallow dish and standard flash cube:    90
  Shallow cylindrical reflector:           65

You likely have a very wide angle shallow dish, or the polished bowl. Don't forget, with AG-1B's you must X-sync at 1/30th or you will lose approximately 1 stop of light! Don't set the OM-1n to "FP" as this is for long duration "FP" type bulbs only (e.g., 6B and 26B).

To convert a guide number from ISO 100 other film speeds, multiply by:
  ISO   25:   .50
  ISO   32:   .56
  ISO   40:   .63
  ISO   50:   .71
  ISO   64:   .80
  ISO   80:   .90
  ISO  100:  1.00
  ISO  125:  1.12
  ISO  160:  1.25
  ISO  200:  1.40
  ISO  250:  1.60
  ISO  320:  1.80
  ISO  400:  2.00
  ISO  500:  2.25
  ISO  640:  2.50
  ISO  800:  2.80
  ISO 1000:  3.20
  ISO 1250:  3.60
  ISO 1600:  4.00
  ISO 2000:  4.50
  ISO 2500:  5.00
  ISO 3200:  5.60
Note:  these approximate multipliers are sufficiently accurate.

-- John


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