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08-26-2008, 11:14 AM   #1
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Why does my Jupiter - 9 read as 1.4?

using the jupiter - 9 (m42 mount using an adaptor) at wide open makes the camera think it is shooting at F1.4, and i think this is impacting on its metering.

anyone have any similar experience with M42 lenses?

08-26-2008, 11:51 AM   #2
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It seems to happen to a degree with several lenses, I'm not sure why either. The Voigtlander 125/2.5 registers as a 2.4, though that would be harder to note the impact on metering. I also wish we had control over the SR focal length choices. My 25 is a 24, the 125 is a 120 and my 90 is an 85...

Also curious to hear reasoning.
08-26-2008, 11:56 AM   #3
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QuoteOriginally posted by thePiRaTE!! Quote
It seems to happen to a degree with several lenses, I'm not sure why either. The Voigtlander 125/2.5 registers as a 2.4, though that would be harder to note the impact on metering. I also wish we had control over the SR focal length choices. My 25 is a 24, the 125 is a 120 and my 90 is an 85...

Also curious to hear reasoning.
also i would like to note,

the jupiter has no connections and no aperture lever, so as far as i know the camera is simply measuring light hitting the sensor... hmmm

is it possible that a FF lens is giving the cropped sensor more light in relative terms? (hope that made sense?)
08-26-2008, 11:56 AM   #4
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maybe an effect of your mount mod?

08-26-2008, 11:58 AM   #5
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QuoteOriginally posted by k100d Quote
maybe an effect of your mount mod?
drilling a small hole in the side of the lens?
08-26-2008, 12:03 PM   #6
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perhaps when the body engages the locking pin ... something happens? i'm totally guessing here
08-26-2008, 12:12 PM   #7
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just did a couple of quick tests, here are observations


without any lens, taking a picture in AV mode with the locking pin UP and DOWN makes the camera read "F -----"

and for some reason i think there are no electronic connections related to the locking pin, i think its purely mechanical.


when i take the jupiter, and change apertures in Av mode (remember that with the Jupiter the aperture is changed on the front of the barrel by a sneaky mechanism, there are no aperture levers)

any pictures taken are metered according to the aperture selected (and subsequently darker view finder)

howver all images read as "F 1.4"


put on my FA43, keep the camera in Av mode but start twisting the aperture ring

no matter what aperture i select manually it stays wide open (as it should) and reads F 1.9 (as it should)


yeah so ... i dont get it... hahaha, why is the Jupiter reading at F1.4 which is a pretty significant way off from F2.0!
08-26-2008, 12:23 PM   #8
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QuoteOriginally posted by Gooshin Quote
drilling a small hole in the side of the lens?
For every hole you drill you gain .1 stop.



08-26-2008, 12:25 PM   #9
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!!!!!!!




*runs off to drill more holes
08-26-2008, 12:28 PM   #10
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I don't understand any of this. None of my manual lenses show anything other than( -- )on the camera.
08-26-2008, 12:29 PM   #11
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QuoteOriginally posted by konraDarnok Quote
I don't understand any of this. None of my manual lenses show anything other than( -- )on the camera.
what mode are you shooting in?
08-26-2008, 12:50 PM   #12
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It doesn't matter what mode I'm in. I assume an 'A' lens would show the apature, but my m42 and 'M' lenses do not register any apature reading on the camera. Ever.
08-26-2008, 12:52 PM   #13
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what camera?

try taking a picture with an M42 lens right now, review it, and hit "info".
08-26-2008, 12:54 PM   #14
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This has happened to me too with some M series lens and when I mounted the lens on my friends K100d, it didn't happen. Weird.
08-26-2008, 12:56 PM   #15
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QuoteOriginally posted by Gooshin Quote
what camera?

try taking a picture with an M42 lens right now, review it, and hit "info".
K10D. My m42 lenses do not have aperture data attached to them.
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