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Photography Question 
Bonnie Porter
 

GE film exposure values --> ISO???


Hi, my dad gave me a giant sack of old photo equipment which is nice. It even has an old selenium light meter in there that works fine and looks like a tiny reincarnation of a Studebaker. But it's GE circa early 50s and they use their own film value index... does anyone know how to convert this into ISO? It goes from 1/3000 to 120.
I am bummed, I was psyched to get a light meter.


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3/25/2008 9:17:53 PM

 
Mark Feldstein
BetterPhoto Member Since: 3/17/2005
  Greetings Bonnie ! I'm not sure whether you need to convert the GE values. It could be that the "film value index" is the same film speed value as ISO/ASA because insofar as I can recall, (yikes !) ASA (American Standard Assoc.) film speeds were used back in the 50's.

One easy way to find out is to set a film speed like 200 in the GE meter and then in another meter (borrowed from someone or at a camera store) get a piece of gray card and meter a scene and see how close the readings are at some f-stop like say f8.0.

If it seems to work, you could try to make your own conversion chart using another light meter, (I'd recommend an analog meter vs. a digital). That's going to be tricky as two meters rarely record the same scene exactly alike and always produce a slightly different reading.

OTOH, while you still see some restored Studebakers running around and they are great cars, that GE meter may have seen its heyday and may be more effective as a conversation piece in a quiet retirement. If you were referring to camera speeds as low as 1/120th, that doesn't help a lot these days when most hand held meters go into shutter speeds of seconds or minutes. I also don't know whether your meter has retained its sensitivity for accurate readings because selenium cells tend to do that after awhile. Alan Marcus would know more about that. Maybe even about the GE meter in particular. If he doesn't come along here, drop him an e-mail.

Lastly, if you can really use a light meter, and IMO they're extremely handy (especially with film) you can get some good Gossen Luna Six or Luna Pro meters, even a Gossen Super Pilot on E-bay pretty cheap. Or, try KEH.com. Probably about $40-60 bucks. Not fancy but they're extremely durable and accurate.
Take it light ;>)
Mark


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3/26/2008 9:41:23 AM

 
Alan N. Marcus   Hi Bonnie,

ASA = 0.8 GE i.e. 100 ASA = 80 GE
GE = 1.25 ASA i.e 100 GE = 125 ASA

ASA and ISO interchangeable

That being said: It is unlikely the old GE continues to give reliable information. I suggest that you consign it to a reverent place in a windowpane cabinet.

The meters of that period are based on the photovoltaic selenium cell. Selenium is the stuff that today we make solar cells out of. The cell in the GE meter generates electricity in proportion to the amount of light striking the cell. This current is measured and displayed via a needle movement. The scale under the needle indicates exposure. The needle movement is bring about by electromagnetism. The voltage / current is low. To make the needle respond it swings on a low friction jewel movement a design borrowed from pocket watch lubricated with sperm whale oil, it has long since dried up.

When in its prime, itís response was a good one for the human eye but not for film, you will find two GE numbers for each black and white film, one for daylight, one for tungsten light. Both were needed because tungsten is deficient in blue and daylight is abundant in blue.

Alan Marcus (marginal technical gobbledygook)
ammarcus@earthlink.net


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3/26/2008 12:01:54 PM

 
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