Why won't my adapted Leica R lenses meter?

Ruhayat · 06-28-2014, 12:53 PM - **1 Like**

Hello all,

I'm curious about something. I adapted two Leica R lenses using two generic LR-to-PK adapter mounts (bought separately). Then I tried them on some K mount cameras. But none of them would meter with the lenses attached (the "can't meter" lights would flicker on all of the cameras).

1. The cameras will meter and work with native K mount lenses.
2. The cameras will also meter and work with m42 lenses (adapted using both original Pentax and generic adapters).
3. The cameras will even meter with unadapted Nikon mount lenses!
4. The R lenses will meter and work on Canon and Nikon cameras.

I am curious to understand why this happens. Do I need a special kind of mount adapter? Or do K mount cameras just do not meter for lenses with particular types of K mounts (if so, what would that be)?

These are the cameras I have tried the lenses with:
Pentax K-r
Pentax K5
Pentax P30
Pentax MX
Pentax ME Super
Ricoh KR5 Super II

I'd really like to use the 28mm Elmarit on the compact Pentax MX body and 50mm Summicron on the Pentax P30. So I am grateful for any pointers or advice.

Thanks in advance.

Parallax · 06-28-2014, 12:58 PM

https://www.pentaxforums.com/forums/58-pentax-beginners-corner-q/110658-using...x-dslrs-f.html

Ruhayat · 06-28-2014, 01:05 PM

Thanks for the link! Now the lenses seem to work on the K5 (well, I set it on A mode, snap a photo and it comes out properly exposed, at any rate). Haven't tried it on the K-r as it's not mine, but as long as it works on my K5 I'm happy.

The lenses are still not metering on the film bodies, though. (There's no "Shoot without lens" menu item to select, hehe).

And the thread I skimmed through doesn't seem to touch on film bodies. Ah well. I'll read through more thoroughly later.

Adam · 06-28-2014, 02:37 PM

Originally posted by Ruhayat

And the thread I skimmed through doesn't seem to touch on film bodies. Ah well. I'll read through more thoroughly later.

On film bodies, non-Pentax lenses need to have manual aperture diaphragms and aperture rings in order to meter properly (otherwise, the camera will assume wide-open exposure). Stop-down metering is not a supported feature since film bodies weren't "crippled". Then just shoot away in Tv or M mode

Adam
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Ruhayat · 06-28-2014, 04:12 PM

Originally posted by Adam

On film bodies, non-Pentax lenses need to have manual aperture diaphragms and aperture rings in order to meter properly (otherwise, the camera will assume wide-open exposure). Stop-down metering is not a supported feature since film bodies weren't "crippled". Then just shoot away in Tv or M mode

Do you mean they need those pin thingies like on the m42 lenses? Because the Leica R system didn't have autofocus, so all the lenses have manual apertures and aperture rings. On the K5 they work correctly now with aperture priority (and manual, of course). No problems.

The main point is that on the K5 the meter works. On the film bodies the meter won't work, period. It doesn't matter whether I stop down the apertures or not, the LED just blinks the way it does when the camera can't meter.

I have been using the 28mm Elmarit-R on the Pentax MX using Sunny 16 and it exposes according to whatever I set, meaning the lens works on the body and the camera lets in light through the lens. It's just that the built-in meter doesn't function, which is a great incovenience. So it's either Sunny 16 or carrying an external meter (which I don't have).

**Just1MoreDave** · 06-28-2014, 04:14 PM - **1 Like**

Originally posted by Ruhayat

Thanks for the link! Now the lenses seem to work on the K5 (well, I set it on A mode, snap a photo and it comes out properly exposed, at any rate). Haven't tried it on the K-r as it's not mine, but as long as it works on my K5 I'm happy.

The lenses are still not metering on the film bodies, though. (There's no "Shoot without lens" menu item to select, hehe).

And the thread I skimmed through doesn't seem to touch on film bodies. Ah well. I'll read through more thoroughly later.

The film cameras you list all have a tab in the upper right of the mount that fits into a slot in a real K mount lens. The slot has a corresponding tab that moves with the aperture ring on the lens. When the aperture ring is set to something like f5.6, the camera's tab moves right along with it. The camera's meter reads that tab position so it knows what aperture the lens is set to, while the lens is still wide open on the camera for focusing.

Your LR to K adapter may not be setting this tab correctly. The Pentax M42 to K adapter moves it all the way to one side when the adapter is installed, so the camera's meter thinks the lens is wide open. Then you use stop-down metering on the lens. But if the tab doesn't move, the meter will be wrong.

My theory sounds great except for Nikon lenses work. I don't have any Nikon lenses or batteries to test in my film camera. So it's just an idea.

Adam · 06-28-2014, 04:30 PM

Originally posted by Ruhayat

Do you mean they need those pin thingies like on the m42 lenses? Because the Leica R system didn't have autofocus, so all the lenses have manual apertures and aperture rings. On the K5 they work correctly now with aperture priority (and manual, of course). No problems.

Basically, the requirement is that the aperture diaphragm needs to close as you turn the aperture ring. If it stays open or is held open by the camera, metering won't work.

Back in the day, for cameras that didn't support open-aperture metering, Takumar lenses had a A/M diaphragm clutch.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)

PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

**TomB_tx** · 06-28-2014, 04:30 PM

Yes - the Leica R lenses will stop down as the aperture ring is moved when on an adapter mount, as there is no camera linkage to open the diaphragm. So it should meter just like an M42 Super Takumar on Manual setting. Don't operate the Depth-of-field preview lever; just set the aperture ring on the desired f-stop. Used that way both my MX and LX will meter properly with these lenses. (If I press the DOF preview lever as I would to stop down a K-mount lens the metering is way off.)
I don't have any Pentax film bodies newer than the LX - so later models could have other issues.
I haven't "Leitaxed" my R lenses as I still shoot them on film with Leica R bodies - which are pretty cheap these days. I plan to get a Sony A7 to use them on digital, rather than adapt them to K mount.

Not a Number · 06-28-2014, 04:35 PM

Here is a K1000 body with and without the M42 adapter installed. The arrow indicates how the adapter engages the aperture control lever. If the LR to PK adapter does not engage the lever in a similar manner then stop down metering will not work.

The adapter should work in any of the "crippled" autofocus bodies (MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60, *ist).

Ruhayat · 06-29-2014, 04:33 AM

Originally posted by Not a Number

Here is a K1000 body with and without the M42 adapter installed. The arrow indicates how the adapter engages the aperture control lever. If the LR to PK adapter does not engage the lever in a similar manner then stop down metering will not work.
The adapter should work in any of the "crippled" autofocus bodies (MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60, *ist).

I see. I have noticed that tab before and always wondered what it did. Never realised that the original Pentax m42 adapter I have drags it along as it is set in. Heheh.

Thank you all for the info. I will digest this and fiddle around with the film cameras and lenses. If I can finally use the 50mm Cron on Pentax P30 with metering -- better yet, 28mm Elmarit on Pentax ME Super and get an ultra compact, AE point and shoot! -- I would be ecstatic.

06-28-2014, 12:53 PM - 1 Like	#1
Ruhayat New Member Join Date: Nov 2012 Posts: 7	Why won't my adapted Leica R lenses meter? Hello all, I'm curious about something. I adapted two Leica R lenses using two generic LR-to-PK adapter mounts (bought separately). Then I tried them on some K mount cameras. But none of them would meter with the lenses attached (the "can't meter" lights would flicker on all of the cameras). 1. The cameras will meter and work with native K mount lenses. 2. The cameras will also meter and work with m42 lenses (adapted using both original Pentax and generic adapters). 3. The cameras will even meter with unadapted Nikon mount lenses! 4. The R lenses will meter and work on Canon and Nikon cameras. I am curious to understand why this happens. Do I need a special kind of mount adapter? Or do K mount cameras just do not meter for lenses with particular types of K mounts (if so, what would that be)? These are the cameras I have tried the lenses with: Pentax K-r Pentax K5 Pentax P30 Pentax MX Pentax ME Super Ricoh KR5 Super II I'd really like to use the 28mm Elmarit on the compact Pentax MX body and 50mm Summicron on the Pentax P30. So I am grateful for any pointers or advice. Thanks in advance.

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06-28-2014, 12:58 PM	#2
Parallax Senior Moderator Loyal Site Supporter Join Date: Apr 2008 Location: South Dakota Photos: Gallery Posts: 19,333	https://www.pentaxforums.com/forums/58-pentax-beginners-corner-q/110658-using...x-dslrs-f.html

06-28-2014, 01:05 PM	#3
Ruhayat New Member Join Date: Nov 2012 Posts: 7 Original Poster	Thanks for the link! Now the lenses seem to work on the K5 (well, I set it on A mode, snap a photo and it comes out properly exposed, at any rate). Haven't tried it on the K-r as it's not mine, but as long as it works on my K5 I'm happy. The lenses are still not metering on the film bodies, though. (There's no "Shoot without lens" menu item to select, hehe). And the thread I skimmed through doesn't seem to touch on film bodies. Ah well. I'll read through more thoroughly later.

06-28-2014, 02:37 PM	#4
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Originally posted by Ruhayat And the thread I skimmed through doesn't seem to touch on film bodies. Ah well. I'll read through more thoroughly later. On film bodies, non-Pentax lenses need to have manual aperture diaphragms and aperture rings in order to meter properly (otherwise, the camera will assume wide-open exposure). Stop-down metering is not a supported feature since film bodies weren't "crippled". Then just shoot away in Tv or M mode Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-28-2014, 04:12 PM	#5
Ruhayat New Member Join Date: Nov 2012 Posts: 7 Original Poster	Originally posted by Adam On film bodies, non-Pentax lenses need to have manual aperture diaphragms and aperture rings in order to meter properly (otherwise, the camera will assume wide-open exposure). Stop-down metering is not a supported feature since film bodies weren't "crippled". Then just shoot away in Tv or M mode Do you mean they need those pin thingies like on the m42 lenses? Because the Leica R system didn't have autofocus, so all the lenses have manual apertures and aperture rings. On the K5 they work correctly now with aperture priority (and manual, of course). No problems. The main point is that on the K5 the meter works. On the film bodies the meter won't work, period. It doesn't matter whether I stop down the apertures or not, the LED just blinks the way it does when the camera can't meter. I have been using the 28mm Elmarit-R on the Pentax MX using Sunny 16 and it exposes according to whatever I set, meaning the lens works on the body and the camera lets in light through the lens. It's just that the built-in meter doesn't function, which is a great incovenience. So it's either Sunny 16 or carrying an external meter (which I don't have).

06-28-2014, 04:14 PM - 1 Like	#6
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	Originally posted by Ruhayat Thanks for the link! Now the lenses seem to work on the K5 (well, I set it on A mode, snap a photo and it comes out properly exposed, at any rate). Haven't tried it on the K-r as it's not mine, but as long as it works on my K5 I'm happy. The lenses are still not metering on the film bodies, though. (There's no "Shoot without lens" menu item to select, hehe). And the thread I skimmed through doesn't seem to touch on film bodies. Ah well. I'll read through more thoroughly later. The film cameras you list all have a tab in the upper right of the mount that fits into a slot in a real K mount lens. The slot has a corresponding tab that moves with the aperture ring on the lens. When the aperture ring is set to something like f5.6, the camera's tab moves right along with it. The camera's meter reads that tab position so it knows what aperture the lens is set to, while the lens is still wide open on the camera for focusing. Your LR to K adapter may not be setting this tab correctly. The Pentax M42 to K adapter moves it all the way to one side when the adapter is installed, so the camera's meter thinks the lens is wide open. Then you use stop-down metering on the lens. But if the tab doesn't move, the meter will be wrong. My theory sounds great except for Nikon lenses work. I don't have any Nikon lenses or batteries to test in my film camera. So it's just an idea.

06-28-2014, 04:30 PM	#7
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Originally posted by Ruhayat Do you mean they need those pin thingies like on the m42 lenses? Because the Leica R system didn't have autofocus, so all the lenses have manual apertures and aperture rings. On the K5 they work correctly now with aperture priority (and manual, of course). No problems. Basically, the requirement is that the aperture diaphragm needs to close as you turn the aperture ring. If it stays open or is held open by the camera, metering won't work. Back in the day, for cameras that didn't support open-aperture metering, Takumar lenses had a A/M diaphragm clutch. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-28-2014, 04:30 PM	#8
TomB_tx Loyal Site Supporter Join Date: Jun 2011 Location: Texas Photos: Gallery Posts: 1,446	Yes - the Leica R lenses will stop down as the aperture ring is moved when on an adapter mount, as there is no camera linkage to open the diaphragm. So it should meter just like an M42 Super Takumar on Manual setting. Don't operate the Depth-of-field preview lever; just set the aperture ring on the desired f-stop. Used that way both my MX and LX will meter properly with these lenses. (If I press the DOF preview lever as I would to stop down a K-mount lens the metering is way off.) I don't have any Pentax film bodies newer than the LX - so later models could have other issues. I haven't "Leitaxed" my R lenses as I still shoot them on film with Leica R bodies - which are pretty cheap these days. I plan to get a Sony A7 to use them on digital, rather than adapt them to K mount.

06-28-2014, 04:35 PM	#9
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Here is a K1000 body with and without the M42 adapter installed. The arrow indicates how the adapter engages the aperture control lever. If the LR to PK adapter does not engage the lever in a similar manner then stop down metering will not work. The adapter should work in any of the "crippled" autofocus bodies (MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60, *ist).

06-29-2014, 04:33 AM	#10
Ruhayat New Member Join Date: Nov 2012 Posts: 7 Original Poster	Originally posted by Not a Number Here is a K1000 body with and without the M42 adapter installed. The arrow indicates how the adapter engages the aperture control lever. If the LR to PK adapter does not engage the lever in a similar manner then stop down metering will not work. The adapter should work in any of the "crippled" autofocus bodies (MZ-30/ZX-30, MZ-50/ZX-50, MZ-60/ZX-60, *ist). I see. I have noticed that tab before and always wondered what it did. Never realised that the original Pentax m42 adapter I have drags it along as it is set in. Heheh. Thank you all for the info. I will digest this and fiddle around with the film cameras and lenses. If I can finally use the 50mm Cron on Pentax P30 with metering -- better yet, 28mm Elmarit on Pentax ME Super and get an ultra compact, AE point and shoot! -- I would be ecstatic.