Why does my Jupiter - 9 read as 1.4?

Gooshin · 08-26-2008, 11:14 AM

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?

thePiRaTE!! · 08-26-2008, 11:51 AM

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.

Gooshin · 08-26-2008, 11:56 AM

Originally posted by thePiRaTE!!

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?)

k100d · 08-26-2008, 11:56 AM

maybe an effect of your mount mod?

Gooshin · 08-26-2008, 11:58 AM

Originally posted by k100d

maybe an effect of your mount mod?

drilling a small hole in the side of the lens?

k100d · 08-26-2008, 12:03 PM

perhaps when the body engages the locking pin ... something happens? i'm totally guessing here

Gooshin · 08-26-2008, 12:12 PM

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!

**rparmar** · 08-26-2008, 12:23 PM

Originally posted by Gooshin

drilling a small hole in the side of the lens?

For every hole you drill you gain .1 stop.

Gooshin · 08-26-2008, 12:25 PM

!!!!!!!

*runs off to drill more holes

konraDarnok · 08-26-2008, 12:28 PM

I don't understand any of this. None of my manual lenses show anything other than( -- )on the camera.

Gooshin · 08-26-2008, 12:29 PM

Originally posted by konraDarnok

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?

konraDarnok · 08-26-2008, 12:50 PM

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.

Gooshin · 08-26-2008, 12:52 PM

what camera?

try taking a picture with an M42 lens right now, review it, and hit "info".

pasipasi · 08-26-2008, 12:54 PM

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.

konraDarnok · 08-26-2008, 12:56 PM

Originally posted by Gooshin

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.

08-26-2008, 11:14 AM	#1
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610	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?

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08-26-2008, 11:51 AM	#2
thePiRaTE!! Inactive Account Join Date: Sep 2007 Location: Calgary, AB Photos: Gallery Posts: 942	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
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610 Original Poster	Originally posted by thePiRaTE!! 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
k100d Veteran Member Join Date: Feb 2008 Location: Toronto Posts: 3,911	maybe an effect of your mount mod?

08-26-2008, 11:58 AM	#5
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610 Original Poster	Originally posted by k100d maybe an effect of your mount mod? drilling a small hole in the side of the lens?

08-26-2008, 12:03 PM	#6
k100d Veteran Member Join Date: Feb 2008 Location: Toronto Posts: 3,911	perhaps when the body engages the locking pin ... something happens? i'm totally guessing here

08-26-2008, 12:12 PM	#7
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610 Original Poster	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
rparmar Site Supporter Join Date: Jan 2008 Photos: Gallery Posts: 8,819	Originally posted by Gooshin 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
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610 Original Poster	!!!!!!! *runs off to drill more holes

08-26-2008, 12:28 PM	#10
konraDarnok Veteran Member Join Date: Aug 2007 Photos: Albums Posts: 969	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
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610 Original Poster	Originally posted by konraDarnok 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
konraDarnok Veteran Member Join Date: Aug 2007 Photos: Albums Posts: 969	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
Gooshin Veteran Member Join Date: Sep 2007 Location: Toronto, the one in Canada. Posts: 5,610 Original Poster	what camera? try taking a picture with an M42 lens right now, review it, and hit "info".

08-26-2008, 12:54 PM	#14
pasipasi Veteran Member Join Date: Feb 2008 Location: Oulu Photos: Gallery Posts: 532	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
konraDarnok Veteran Member Join Date: Aug 2007 Photos: Albums Posts: 969	Originally posted by Gooshin 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.