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  1. #21

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    Here is a photo of the guide number info. on an old* box of GE M2 bulbs. See the note about the reduced guide number when using an adapter for this small bulb when used in a flash made for the larger No. 5 or Press 25 bulbs. For those not skilled at guide number calculations; you loose about one stop of light with an adapter.

    *Back before they changed the film speed rating system and Tri-X was only rated at 200. If anyone knows when they revised the system by how they set film speed and any details please let me know. If nothing else it will help me date this box of flashbulbs.
    Attached Thumbnails Attached Thumbnails GE PowerMite M2 Flashbulb Guide number.jpg  
    Last edited by brianmquinn; 03-31-2011 at 09:15 PM. Click to view previous post history.

  2. #22

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    continue...

    What about these:

    1. Does it mean that if the flash unit can take GE No. 5 , then it surely can take Sylvania Press 25 or other bulbs that has boyanet base?

    2. What is the different between M2, M3 or M25?

    3. Why don't we just use Blue bulb since it can be used when taking both B&W and color photo. Why is clear bulb needed since it is only used on taking B&W?

    Thanks guys!
    Last edited by windly9; 04-02-2011 at 08:07 AM. Click to view previous post history.

  3. #23

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    Questions...

    Quote Originally Posted by brianmquinn View Post
    Here is a photo of the guide number info. on an old* box of GE M2 bulbs. See the note about the reduced guide number when using an adapter for this small bulb when used in a flash made for the larger No. 5 or Press 25 bulbs. For those not skilled at guide number calculations; you loose about one stop of light with an adapter.

    *Back before they changed the film speed rating system and Tri-X was only rated at 200. If anyone knows when they revised the system by how they set film speed and any details please let me know. If nothing else it will help me date this box of flashbulbs.
    Hi, what will happen when adapter is used to install smaller bulb like M2 on Flash unit originally for larger bulb like No.5? Any effects or differences when taking photo? BTW, what is guide number and what are they used for and how to use them?

    You said: "For those not skilled at guide number calculations; you loose about one stop of light with an adapter." >> Do you mind explain it?
    Last edited by windly9; 04-02-2011 at 08:12 AM. Click to view previous post history.

  4. #24

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    Answers:
    1. Does it mean that if the flash unit can take GE No. 5 , then it surely can take Sylvania Press 25 or other bulbs that has boyanet base?
    Any flash that takes a No. 5 will also fit a No. 6 or Press 25 or 26B

    2. What is the different between M2, M3 or M25?
    The M2 is the same size but has less power, and a slightly lower color temp. My first question that started this thread was how do the M3 and M5 or for that matter the M25 differ. So I can’t say exactly.

    3. Why don't we just use Blue bulb since it can be used when taking both B&W and color photo. Why is clear bulb needed since it is only used on taking B&W?
    The blue reduces the light output. You get more power if you use B&W and clear flash. Also when flash bulbs came out it was all for B&W as that was the film at the time. You can use clear flash with a blue filter and color film or skip the filter and use blue flash.

  5. #25

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  6. #26

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    Sorry, i have one question but not related to flash bulb...

    What is frame number(on the backing paper of film roll??) ?

    What are they for?

    Thanks!

  7. #27
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    Most all of the old medium format cameras had a red window on the back of the camera. After each exposure the film was wound to the next number in the window. This was before the more modern cameras that wound to the next frame and then stopped automatically.

  8. #28

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    I finally found the answer to the question that started this thread in some old printed GE information.
    The M5 and M25 were the same size and had the same total light output. Their timing was different. The M25 was 15ms to peak and the M5 was 20ms to peak. The M5 was made to have the same 20ms to peak time that the larger and brighter GE #5 had. The larger GE #5 put out about 25% more light then the M5.
    Simple box cameras of the time ( 1950s ) had fixed shutter speeds of about 1/30 sec. That is about 32ms long. They also had what was in effect X sync. There was no delay in opening the shutter on these simple and cheap cameras. They relied on long shutter speeds for flash sync. They also had small fixed F stops of about F16 to get maximum depth of field with their fixed focus lenses. The reason an M25 bulb was recommended for these simple cameras was all of the flashbulb’s light output would be during that 32ms. With a slower M5 bulb the shutter would close before the bulb burned all the way out. This would result in a reduced guide number for the M5 if used in these simple cameras.

  9. #29

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    flash unit... flash bulb?

    Hi, I've just bought an Argus 75. The flash unit comes with it has a reflector measured about 4.5 inches. Is it considered to be a 5 inches reflector? and what kind of bulb will it take?

  10. #30

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    I can't say for sure without seeing your unit but the Argus units I have seen in the past took the bulbs with pins on the side of their base. That would be the #5 or Press 25 or bantam 8. With an adaptor they could take the M2, M3, M5, M25 bulbs.
    Look on your unit most flashguns gave a distance to subject to use with a listed bulb. The bulb listed is the one you need.

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