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How to use/meter Manual & M42 Lenses on all Pentax DSLRs (K-1, K-3, K-5, K-30, etc)
Posted By: Adam, 08-12-2010, 04:24 AM

Many Pentax DSLR owners want to use M42 screwmount (Takumar) lenses, or M or K manual lenses, on their cameras because of the low cost and relatively high image quality of these lenses.


If you're wondering whether or not these lenses can be used with Pentax DSLRs (or the K-01), then the answer is yes! Pentax as well as third-party manual and screwmount lenses can easily be mounted on any Pentax DSLR (such as the K-50, K-500, K-30, K-5 series, K-r, K-x, K-7, K10D, K100D, K200D, *ist D, etc.) Just follow this guide!



Modern Pentax DSLRs use the Pentax "K-mount", which employs a bayonet and therefore differs significantly from the M42 screw mount. The older manual M and K (SMC Pentax-M, SMC Pentax) lenses actually use the bayonet, so they will not need an adapter - you can skip straight to the lower portion of this article (starting at "Important!") for information on how to meter with those lenses. Screwmount lenses usually have "Takumar" in their names, and in order to mount screwmount lenses on your k-mount body, you'll need a Pentax k to m42 adapter. Pictured above is the genuine Pentax adapter, which is ideally the one you want to get. Unfortunately, it has been discontinued and can only be purchased second-hand. However, similar third-party adapters are also available. Caution: Many third-party adapters, such as this one, have a protruding flange which will prevent you from focusing all the way to infinity. If you want to buy a third-party adapter (they're generally cheaper), make sure that they don't have this flange. Here's an example of a good third-party adapter.

Once you have your adapter, the next step is to install it on your camera (it can easily be put on and removed on-the-fly). Check out the m42 to k adapter manual. After you've installed the adapter, you'll want to mount the lens. This is done by screwing it into the camera until the lens feels firmly attached. The focusing window and lens ring should line up with the camera just like any other lens. Now that your lens is mounted, let's talk about how to take photos with it.

Important! The hard part is to get the camera to actually fire when a manual lens is mounted. In order to accomplish this, enter your camera's custom function menu, select the "Using Aperture Ring" setting (usually at the end of the menu, #21 on the K-7, #27 on the K-5, #27 on the K-3, #26 on the K-1), and set it to 2 (allowed). Once you do this, the shutter will at least fire, as it wouldn't have with this setting disabled (you would simply have seen an F-- indication on the top LCD/info screen). The setting description should read: 'Shutter will release when aperture ring is not set to the "A" position' when "allowed" is selected. Also note that the mount on the lens must be conductive for electrical current so that it shorts the electrical contacts on the camera body. All Pentax manufactured lenses have a conductive mount, but some third party lenses do not in which case the area of the mount touching the contacts must be sanded down.

K-30, K-50, K-500, K-70, K-S1, K-S2 and K-01 users: make sure you also set your green button "action in M/TAv Mode" to Tv SHIFT. This is found under the button customization menu (page 3 of the main menu) on the K-01 or as a custom function on the K-30, K-50 and K-500. On the K-S2 and K-70, look under the e-dial programming sub-menu under button customization in the record menu.

Finally, ensure that auto ISO is disabled.

Now, let's discuss metering. Since manual lenses don't feed aperture data to the camera, the only way for the camera to check how much light is being passed through the lens is to measure the light while the lens is stopped down. Follow this procedure to properly meter with a screwmount, M, or K lens:

___0. Ensure that the "Using Aperture Ring" custom function is set to "2 (allowed)" (K-30/50/500/01 users must also ensure that the green button is configured to Tv Shift in M/TAv Mode) as described above
  1. Set your camera to M mode using the mode dial (your camera won't fire in other modes*)
  2. Compose and focus your image.
  3. Using the aperture ring (the ring at the very back of your lens; it will have numbers such as 2.8, 4, 5.6, 8 written on it), select your desired aperture setting. Note that the smaller the aperture number is, the more light passes through the lens, and the blurrier the out of focus areas of your photograph will be (and vice-versa).
  4. [Screwmount lenses only] Switch the diaphragm clutch on your lens to "Manual" (you can leave it on Auto when composing and focusing if you don't want a dark viewfinder).
  5. Measure the light by either pressing the "Green Button", or pushing your power button to DOF preview mode (only available on high-end bodies). Your camera will automatically set the shutter speed for you.
All that's left now is for you to press the shutter release button to take your photo. Congratulations- you've now learned how to use M42 and M & K manual lenses with Pentax DSLRs!

*Screwmount lenses may also be used in Av mode since they are always stopped down to the aperture you will be shooting at (unlike M&K lenses, which are stopped down only when the shutter is released or when you meter as described above).

Note: if your aperture ring has an "A" on it, instead of doing stop-down metering as per this guide, you'll want to set the ring to "A" and use the camera's scrollweel to adjust the aperture via Av mode.

Click here if you found this article helpful!

Video version:


Last edited by Ole; 02-12-2011 at 11:46 AM.
Views: 249,812
09-15-2014, 04:09 AM   #241
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QuoteOriginally posted by GUB Quote
Thanks for the info Lowell. I see there is quite a few scattered threads about it. Is there a definitive thread you can direct me to?
Thought I would have a bit of an experiment with a pentaxM 50mm f1.7.
Took a range of images comparing LV vs Optical viewfinder metering and comparing using the green button vs my unmounting the lens trick.
I cut and pasted sections of the images to make the chart which I think is about as graphical as a graph.
the exposures range from about 90 to 163 on the greyscale image. (if I am reading things right)
So would that be about a 2 stop range?
The results were not very repeatable. (I went back and did the repeats a bit later)
Interesting that Live View with the lens backed off and set on AV was easily the most consistent.
Live view will be the most consistent, because it uses the sensor not the viewfinder to measure exposure.

For the viewfinder/green button exposure, one thing to consider is to have the EV steps match the lens detects, I.e. 1/2 stops, because otherwise you will have some inconsistencies between the 1/2 stop indexing of the aperture and slight metering changes frame to frame in huge shot.

I have found the method I use to be quite consistent over the span of several years, where I can go back and repeat it, within some tolerances again and again.

10-11-2014, 10:54 AM   #242
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QuoteOriginally posted by Adam Quote
Many Pentax DSLR owners want to use M42 screwmount (Takumar) lenses, or M or K manual lenses, on their cameras because of the low cost and relatively high image quality of these lenses.


If you're wondering whether or not these lenses can be used with Pentax DSLRs (or the K-01), then the answer is yes! Pentax as well as third-party manual and screwmount lenses can easily be mounted on any Pentax DSLR (such as the K-50, K-500, K-30, K-5 series, K-r, K-x, K-7, K10D, K100D, K200D, *ist D, etc.) Just follow this guide!



Modern Pentax DSLRs use the Pentax "K-mount", which employs a bayonet and therefore differs significantly from the M42 screw mount. The older manual M and K (SMC Pentax-M,
SMC Pentax) lenses actually use the bayonet, so they will not need an adapter - you can skip straight to the lower portion of this article (starting at "Important!") for information on how to meter with those lenses. Screwmount lenses usually have "Takumar" in their names, and in order to mount screwmount lenses on your k-mount body, you'll need a Pentax k to m42 adapter. Pictured above is the genuine Pentax adapter, which is ideally the one you want to get. Unfortunately, it has been discontinued and can only be purchased second-hand. However, similar third-party adapters are also available. Caution: Many third-party adapters, such as this one, have a protruding flange which will prevent you from focusing all the way to infinity. If you want to buy a third-party adapter (they're generally cheaper), make sure that they don't have this flange. Here's an example of a good third-party adapter.

Once you have your adapter, the next step is to install it on your camera (it can easily be put on and removed on-the-fly). Check out the
m42 to k adapter manual. After you've installed the adapter, you'll want to mount the lens. This is done by screwing it into the camera until the lens feels firmly attached. The focusing window and lens ring should line up with the camera just like any other lens. Now that your lens is mounted, let's talk about how to take photos with it.

Important! The hard part is to get the camera to
actually fire when a manual lens is mounted. In order to accomplish this, enter your camera's custom function menu, select the "Using Aperture Ring" setting (usually at the end of the menu, #21 on the K-7, #27 on the K-5, #27 on the K-3), and set it to 2 (allowed). Once you do this, the shutter will at least fire, as it wouldn't have with this setting disabled (you would simply have seen an F-- indication on the top LCD/info screen). The setting description should read: 'Shutter will release when aperture ring is not set to the "A" position' when "allowed" is selected. Also note that the mount on the lens must be conductive for electrical current so that it shorts the electrical contacts on the camera body. All Pentax manufactured lenses have a conductive mount, but some third party lenses do not in which case the area of the mount touching the contacts must be sanded down.

K-30, K-50, K-500, K-S1 and K-01 users:
make sure you also set your green button "action in M/TAv Mode" to Tv SHIFT. This is found under the button customization menu (page 3 of the main menu) on the K-01 or as a custom function on the K-30, K-50 and K-500. Also, avoid auto ISO.

Now, let's discuss metering. Since manual lenses don't feed aperture data to the camera, the only way for the camera to check how much light is being passed through the lens is to measure the light while the lens is stopped down. Follow this procedure to properly meter with a screwmount, M, or K lens:


___0. Ensure that the "Using Aperture Ring" custom function is set to "2 (allowed)" (K-30/50/500/01 users must also ensure that the green button is configured to Tv Shift in M/TAv Mode) as described above
  1. Set your camera to M mode using the mode dial (your camera won't fire in other modes*)
  2. Compose and focus your image.
  3. Using the aperture ring (the ring at the very back of your lens; it will have numbers such as 2.8, 4, 5.6, 8 written on it), select your desired aperture setting. Note that the smaller the aperture number is, the more light passes through the lens, and the blurrier the out of focus areas of your photograph will be (and vice-versa).
  4. [Screwmount lenses only] Switch the diaphragm clutch on your lens to "Manual" (you can leave it on Auto when composing and focusing if you don't want a dark viewfinder).
  5. Measure the light by either pressing the "Green Button", or pushing your power button to DOF preview mode (only available on select bodies). Your camera will automatically set the shutter speed for you.
All that's left now is for you to press the shutter release button to take your photo. Congratulations- you've now learned how to use M42 and M & K manual lenses with Pentax DSLRs!

*Screwmount lenses may also be used in Av mode since they are always stopped down to the aperture you will be shooting at (unlike M&K lenses, which are stopped down only when the shutter is released or when you meter as described above).

Note: if your aperture ring has an "A" on it, instead of doing stop-down metering as per this guide, you'll want to set the ring to "A" and use the camera's scrollweel to adjust the aperture via Av mode.


Click here
if you found this article helpful!

Video version:
How to use a manual lens (M, K, or M42) on a Pentax DSLR - YouTube
On my Kx, I have to push the exposure compensation button,(the green button doesn't have what you listed as an option) then the camera will set the shutter speed, but only in manual mode, not Av mode.
Thank you for this tutorial, I figured there had to be a way to use the light meter with my old lens, but couldn't find how! Please add use the exp comp button for Kx users to your post.
10-13-2014, 08:26 AM   #243
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Great guide, thanks Adam
10-25-2014, 10:41 PM   #244
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QuoteOriginally posted by altopiet Quote
Manual lenses can only be used in M and AV modes. If you put it in TAv, Tv or Sv modes it will revert to Av mode. In K, M and M42 lenses in Auto mode, will always be wide open in Av mode. If you put them in M mode you first manually set your aperture on the ring to the desired aperture and the desired ISO, then press the green button while aiming toward the target, which will stop down to the aperture setting picked by you, take a light measurement and taking into account the ISO setting you picked, decide on a suitable shutter speed to capture a correctly exposed image. Using a pre-set or M42 lens in manual mode, you can use Av mode. As there is no aperture lever to be stopped down, what you see through the VF, or live view, is what you get. When you stop down on the aperture ring you'll see it get darker and the shutter speed changing accordingly, adapting to the aperture getting smaller. You can change the shutter speed, but will not get a correctly exposed image
This is what i was looking for!! Thanks.
I have a cat 500 f8 lens and a 650-1300 f8-f11 lens and I have been leaving mode on P, (it reverts to Av) and I can get focus confirm on the 500, and below about 800 on the zoom. I left the green button set to program line, and it sets the shutter for me just fine.
I am shooting a K-30 with firmware 1.05
One thing I notice is that I do NOT get exposure bars. Nor do I get any reading of the aperture (which makes sense, as there are no contacts to read lens data from) Nor does my EXIF data record aperture info.
I wish I could get that aperture data in camera somehow and on EXIF. The cat is no prob, as I know it is 8, always, but the zoom changes the aperture value, as it is zoomed in and out. Not sure there could be any way, but I would like it anyways.
I am just happy to get confirmation that a preset lens works fine in Av mode with green button set to program line.

10-26-2014, 09:31 AM   #245
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Because of the "crippled" K-mount there is no way for the body to know what f-stop is set unless it is an "A" type lens in the "A" mode.

You'll just have to resort to the old fashioned method of using a notebook. I suppose you could record a short video with spoken comments. EXIF can hold audio comments but I don't think any of the Pentax bodies allow you to record audio into EXIF.
11-17-2014, 09:21 PM   #246
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Ok, all apologies if this was covered and I missed it. I've read this great thread on using manual lenses on my Pentax K-3, and had success with almost all of my manual lenses (Access P-MC 70-210mm 1:3.5, MC Cosmicar 70-200mm 1:4, MC Cosmicar 28-80mm 1:3.5-4.5 and Super Takumar 50mm 1:1.4 M42 mount); all work well. However, when I try my Vivitar 50mm 1:2.0 lens, I lose control of the aperature ring. It does have the black surface and from the sounds of it, I should just drill another stop in it. Sounds good.

But, this lens works just fine on my K-01 and on my K-200D using the instructions provided herein. Why wouldn't the K-3?!?

I bought a Spyder LensCal and have been taking pictures of it for lens adjustment as well as to establish the sharpness envelope of each lens (including my 43mm Ltd, 40mm XS, 18-55 WR zoom and Sigma 50-200). Interesting results...

Thanks
Z
11-18-2014, 01:57 AM   #247
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QuoteOriginally posted by HomeMadeSin Quote
But, this lens works just fine on my K-01 and on my K-200D using the instructions provided herein. Why wouldn't the K-3?!?
Different models handle non-conductive lens mounts differently - it may also be a matter of the firmware version too. The easiest way to check this is to put a piece of metal foil over the the contacts and mount the lens.
11-18-2014, 02:16 AM   #248
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Here is my problem with a smc pentax A50 f/1.4 mounted to a k-5ii.
- lens aperture ring allowed, camera body focus switch in M, mode switch in M
- aperture on lens set to any non 'A' value, compose & focus, green button to meter, and shutter release - works
- aperture on lens set to 'A', mode switch to 'Av' - the rear wheel does not change the aperture value nor does the lcd show the aperture value - am I wrong to expect to see the aperture display in the lcd, or is my lens not working as it should?

Cheers

11-18-2014, 03:05 AM - 1 Like   #249
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QuoteOriginally posted by PbR Quote
aperture on lens set to 'A', mode switch to 'Av' - the rear wheel does not change the aperture value nor does the lcd show the aperture value - am I wrong to expect to see the aperture display in the lcd, or is my lens not working as it should?
The eDial should change the f-stop which should show on the display. If all you see is "F --" then something is wrong. Try "working/jiggling" the lens gently in the mount might free or align the pins properly. If that doesn't help remove the lens and see if the "A" pin extends and retracts when you switch to and from "A" mode. If it appears to be working properly try cleaning the contacts on both the lens and the camera body. Wiping with a lint free cloth should be sufficient but you might want to slightly moisten the cloth with some contact cleaner, lighter fluid or rubbing alcohol. Do not use so much fluid so that it seeps into the contacts.

If this fails it may be that some grease has gotten into the "A" pin internally. You would have to disassemble the "A" pin and clean it. This can be tricky as the "A" pin assembly can be as much as 4 very tiny bits that are difficult to manipulate and are easily lost. If the 1.4 is like the 1.7 you should be able to remove the pin assembly and the associated contact plate without removing the aperture ring. That way you don't have to worry about losing the small ball bearing at fussing with getting the ring back on without the ball bearing being launched into space. With the ring set in the "A" position you should be able to lift the pin assembly and contact plate out with some fine tweezers after removing the bayonet mount. Clean the parts in some lighter fluid which will dissolve any grease. Then have fun trying to put the assembly back together again. It has a tendency to fall apart easily as it needs tension to hold it together which you can't really supply until it is seated. The only part that should be greased is the where the tab contacts the aperture ring. Or using conductive grease. You might try taping the ring to the body of the lens so you don't accidentally remove the ring and lose the ball bearing.

Last edited by Not a Number; 11-18-2014 at 03:11 AM.
11-18-2014, 10:45 PM   #250
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QuoteOriginally posted by Not a Number Quote
The eDial should change the f-stop which should show on the display. If all you see is "F --" then something is wrong. Try "working/jiggling" the lens gently in the mount might free or align the pins properly. If that doesn't help remove the lens and see if the "A" pin extends and retracts when you switch to and from "A" mode. If it appears to be working properly try cleaning the contacts on both the lens and the camera body. Wiping with a lint free cloth should be sufficient but you might want to slightly moisten the cloth with some contact cleaner, lighter fluid or rubbing alcohol. Do not use so much fluid so that it seeps into the contacts.

If this fails it may be that some grease has gotten into the "A" pin internally. You would have to disassemble the "A" pin and clean it. This can be tricky as the "A" pin assembly can be as much as 4 very tiny bits that are difficult to manipulate and are easily lost. If the 1.4 is like the 1.7 you should be able to remove the pin assembly and the associated contact plate without removing the aperture ring. That way you don't have to worry about losing the small ball bearing at fussing with getting the ring back on without the ball bearing being launched into space. With the ring set in the "A" position you should be able to lift the pin assembly and contact plate out with some fine tweezers after removing the bayonet mount. Clean the parts in some lighter fluid which will dissolve any grease. Then have fun trying to put the assembly back together again. It has a tendency to fall apart easily as it needs tension to hold it together which you can't really supply until it is seated. The only part that should be greased is the where the tab contacts the aperture ring. Or using conductive grease. You might try taping the ring to the body of the lens so you don't accidentally remove the ring and lose the ball bearing.
Thanks for the detailed response.

Wel!, there is no 'A' pin to extend / retract!! Looks like a prior self repair attempt.

Will take it to my local shop.
11-19-2014, 08:20 AM   #251
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QuoteOriginally posted by PbR Quote
Will take it to my local shop.
They probably won't be able to get parts for it. If you are in the US you could try contacting Eric Hendrickson, although he may not have parts either unless taken from a donor lens.

Home
11-19-2014, 09:26 AM   #252
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QuoteOriginally posted by Not a Number Quote
They probably won't be able to get parts for it. If you are in the US you could try contacting Eric Hendrickson, although he may not have parts either unless taken from a donor lens.
I have heard of Eric but have no idea how this works. Is there a thread or background on contacting him and what he does?
11-20-2014, 03:16 AM   #253
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QuoteOriginally posted by Not a Number Quote
They probably won't be able to get parts for it. If you are in the US you could try contacting Eric Hendrickson, although he may not have parts either unless taken from a donor lens.

Home
Will know in 3-4 days, if not fixed, will continue to use it as M lens.
11-20-2014, 04:50 AM   #254
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QuoteOriginally posted by bradshea Quote
I have heard of Eric but have no idea how this works. Is there a thread or background on contacting him and what he does?
Click on the link in my previous post.
11-20-2014, 10:24 AM   #255
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QuoteOriginally posted by Not a Number Quote
Click on the link in my previous post.
AHhhhh!

"HOME" wasn't very descriptive so I assumed it wasn't related. Maybe you could relabel it?
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