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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.
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03-21-2012, 09:04 AM   #76
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Adam,
Thank-you for the instructions. I got my K7 to fire with an Access 28 f2.8 macro lens that is K-mount. When you say...

"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 (#21 on the K-7, #27 on the K-5), and set it to 2 (allowed)."

I found that on my K7 I needed to set the "using aperture ring" on #37 on my K7's custom menu, to 2. Is this a firmware difference or is my camera "special".

04-19-2012, 07:39 PM   #77
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Hello, I've been searching the manual and forum for this. If I've missed it in the manual or the forum please accept my apologies in advance. I'm using a Pentax M 1.7 lens on the K-5 now. Everything is working fine but when I switch to live view mode I can't seem to locate the light meter. I can see the light meter through the viewfinder when I turn the shutter dial to the right but I don't notice a light meter on the LCD during live view. Does this exist?
04-22-2012, 08:04 AM   #78
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QuoteOriginally posted by icedoghans Quote
Adam,

I found that on my K7 I needed to set the "using aperture ring" on #37 on my K7's custom menu, to 2. Is this a firmware difference or is my camera "special".
it is odd, on my K7 it is actually #38 "using aperture ring" ( my firmware is 1.12 )
04-23-2012, 04:51 PM   #79
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Firmware update

Now that I have upgraded my K-7 firmware to 1.12 from 1.00 I confirm that the "Use aperture ring" setting is number 38 (it was 37 in 1.00).

Now I am trying to get my m42 auto lens to meter in M mode like my K-mount manual lens' do. The surgery fires and the focus confirm beeps, and photos look okay... Just I cannot get the meter to fire via the green button. Any ideas?


Last edited by icedoghans; 04-23-2012 at 06:15 PM.
04-23-2012, 08:48 PM   #80
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QuoteOriginally posted by i_trax Quote
it is odd, on my K7 it is actually #38 "using aperture ring" ( my firmware is 1.12 )
It depends on what mode you're in. If you're in Av, for instance, lots of additional e-dial customization options will appear in the custom function menu.

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04-24-2012, 11:04 PM - 1 Like   #81
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M42 lenses

QuoteOriginally posted by icedoghans Quote
Now that I have upgraded my K-7 firmware to 1.12 from 1.00 I confirm that the "Use aperture ring" setting is number 38 (it was 37 in 1.00).

Now I am trying to get my m42 auto lens to meter in M mode like my K-mount manual lens' do. The surgery fires and the focus confirm beeps, and photos look okay... Just I cannot get the meter to fire via the green button. Any ideas?
The most convenient is to use AV with M42 lenses.
Switch the lens to Auto ( wide open) for focusing, switch back to Manual, chose desirable aperture, half press the shutter, camera will do metering and take the picture.
It will take a bit of time to get used to this routine but it is well worthy.
04-26-2012, 03:32 PM   #82
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M 50mm f/1.4 not fully compatible with my K7

After reading all your posts here, I tested my M50 f/1.4 on my K7 yesterday. I followed the instructions in the link from Pentax to the letter. The combination worked well as long as I was shooting in the shade. When I shot subjects under the sun (f/5.6), all were way over-exposed (beyond repair). I repeated the test with my A50mm f/1.7 (same setting, same ISO) and the results were all perfect regardless of the lighting. What am I missing here? I remember getting consistent results with my M50mm on my *ist DS, although I had to lock the exposure after first using the DOF lever. Should I be locking the exposure on the K7 as well before shooting? I'd like to keep the M50mm so any help will be appreciated. Thanks.
04-26-2012, 05:31 PM - 1 Like   #83
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QuoteOriginally posted by el baroda Quote
After reading all your posts here, I tested my M50 f/1.4 on my K7 yesterday. I followed the instructions in the link from Pentax to the letter. The combination worked well as long as I was shooting in the shade. When I shot subjects under the sun (f/5.6), all were way over-exposed (beyond repair). I repeated the test with my A50mm f/1.7 (same setting, same ISO) and the results were all perfect regardless of the lighting. What am I missing here? I remember getting consistent results with my M50mm on my *ist DS, although I had to lock the exposure after first using the DOF lever. Should I be locking the exposure on the K7 as well before shooting? I'd like to keep the M50mm so any help will be appreciated. Thanks.
You need to shoot "Pentax-M" series lenses in "Hyper Manual Mode [M Mode]". The K7 will not stop down the lens in any other mode other than "M" mode, so you have been shooting it wide open, hence the over-exposing...

Edit: This actually applies to ANY K-Mount lens that DOES NOT have "A" Contacts on the lens...

04-26-2012, 07:26 PM   #84
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Hi. As I wrote, I followed everything per Pentax's link, including setting the camera on "M" mode. Thanks.
04-26-2012, 07:47 PM   #85
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QuoteOriginally posted by el baroda Quote
Hi. As I wrote, I followed everything per Pentax's link, including setting the camera on "M" mode. Thanks.
Well, not to be rude or anything, I am telling you what the exact problem is - and in short, if your lens is not broken then I am right. Sit back, take a deep breath, and do the following:

[Note: FYI, I Don't care about what the link says]


1: Make Sure "Using Aperture Ring" Is Set (To True|Yes|On) In Your K7 Settings
2: Mount Your Lens
3: Select "M" Mode On Your Dial
4: Turn Camera On
5: Scroll Select 50mm
6: Select Your Aperture To Shoot At On The Lens
7: Compose Your Scene
8: "Green Button Meter" The Scene
9: If You Haven't Already Done So - Focus
10: Press Shutter
11: Smile, You Just Snapped A Photo
04-26-2012, 08:05 PM   #86
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Thanks a lot, Joe-penn. I appreciate very much your help, but that's exactly what I was doing. I will try again tomorrow with another M 50mm lens and see how it goes. Maybe, my M 50mm f/1.4 is broken or something. Will let you know. Thanks.
04-27-2012, 02:09 AM   #87
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and the Green button in Menu is selected as a Green button function , I do not have my K7 with me but there is a long list of other options.
so when you press green button with your M 50 lens attached and aperture is set to less than full open you can hear a click ( stop down metering) and you can see
a blink in a view finder??
04-27-2012, 05:25 AM   #88
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sorry, I was biased by KX green button options.
in K7 you need to choose number 2 : Tv Shift ( Camera sets shutter speed relative to the selected aperture for proper exposure )
04-28-2012, 11:01 AM   #89
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Great thread! I'm successfully using MFL thanks to this thread. Recently I got Helios 58mm and I can't confirm focal length, so I'm using as 55mm. I know it's important for EXIF data.

Question is any possibility to fine tune focal length?

Thank you!
04-28-2012, 10:11 PM - 1 Like   #90
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it is also important for SR (shake reduction),
as far as I know there is no possibility to fine tune focal lengths, the available values are preloaded and only firmware upgrade can alter them.
You just need to choose the closest one, as you did.
You follow the same principal with manual zooms, choose the closest one to the one actually used.
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