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Newbie question: metering the GG
Dumb newbie again. I'm still waiting for the camera to get here, so I poked
a hole in the bottom of a cardboard crate, and made a viewing screen from sheet mylar and the negative carrier. The 90 f/6.8 seems to cover pretty well even wide open, but I can't tell much about light drop off. While pondering how I would measure this... I can't think of any reason why I can't meter off the groundglass with a spot meter. I understand that a fresnel evens out the GG brightness, so I ordered a fresnel. (eBay, of course.) Would it be reasonable then to meter the GG with the spotmeter? Certainly some adjustment will need to be applied, but it seems this would be a consistent factor. Wouldn't this be useful for figuring enlargement and filter pack losses? It's odd that I haven't come across this in writing, not that my search was very broad or deep. Is it just too obvious to mention? or is there something fundamentally wrong with the idea? Mike. |
#2
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Newbie question: metering the GG
Would it be reasonable then to meter the GG with the spotmeter? Certainly
some adjustment will need to be applied, but it seems this would be a consistent factor. Wouldn't this be useful for figuring enlargement and filter pack losses? Most SLR's with TTL metering that is not done via photosensors behind the mirror via half-silvered mirror, measure the ground glass. And some hand-held meter manufacturers (like Minolta) offer such an attachment for use with their meters. You simply need to calibrate your reading so that you know accurately the correspondence of transmitted light thru the GG to the sensor which is reading the GG, since the GG transmission varies by the design of the GG surface. --Wilt |
#3
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Newbie question: metering the GG
In article ,
"MikeWhy" wrote: Dumb newbie again. I'm still waiting for the camera to get here, so I poked a hole in the bottom of a cardboard crate, and made a viewing screen from sheet mylar and the negative carrier. The 90 f/6.8 seems to cover pretty well even wide open, but I can't tell much about light drop off. While pondering how I would measure this... I can't think of any reason why I can't meter off the groundglass with a spot meter. I understand that a fresnel evens out the GG brightness, so I ordered a fresnel. (eBay, of course.) Would it be reasonable then to meter the GG with the spotmeter? Certainly some adjustment will need to be applied, but it seems this would be a consistent factor. Wouldn't this be useful for figuring enlargement and filter pack losses? It's odd that I haven't come across this in writing, not that my search was very broad or deep. Is it just too obvious to mention? or is there something fundamentally wrong with the idea? Mike. You can meter off the GG with a spot meter, however their will be light lost as a result of the transmitance of the glass, how much is something you"ll have to determine. -- LF website http://members.bellatlantic.net/~gblank |
#4
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Newbie question: metering the GG
Why would you want to meter from the GG? If the bellows factor is confusing, then there are some very simple remedies, 'the stick', mark your rail(s), carry a small tape measure. Then you can use the highly selective, undiminished handheld or spot meter to make better readings. |
#5
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Newbie question: metering the GG
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