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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!

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Last edited by Ole; 02-12-2011 at 11:46 AM.
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01-22-2013, 08:54 PM   #121
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I have a K30 and you state in your instructions, "K-30 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." I can not find anything like this in the menu but the camera seems to operate just fine. I am using the lens off my old ME Super. I set the desired f-stop and press the green button which set the shutter speed and then press the shutter. All this with the camera set on manual.

02-01-2013, 01:41 PM   #122
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QuoteOriginally posted by mspoon Quote
Hi, John J. Yup, I actually did follow your link prior to posting. I just reviewed it again to make sure I didn't miss anything. Green button is set for Tv SHIFT in M mode. "Using Aperture Ring" is set to 2 (Enable). I dialed to M mode and manually set the ISO to 400, not auto. I the pressed the green button. I don't hear any sound of the aperture stopping down, but the shutter speed changes to 1/500 sec.

What's interesting is that no matter what I point the camera at, and whatever I change the aperture to, the shutter speed remains at 1/500, even with subsequent presses of the green button. So I could be pointing it straight at a bright light with an aperture of f/4, or at a dark cabinet in a dim room with an aperture of f/22. The shutter speed always sets itself to 1/500.

Update: I just discovered that things DO work correctly in Live View. I get appropriate shutter speeds on the press of the green button, and they change (again, appropriately) if I change the subject. And, here's the weirdest thing, if I then switch back to the OVF and press the green button, I get an appropriate shutter speed. But then it gets stuck at that same shutter speed until I turn the camera off. If I turn it back on and try the OVF again, pressing the green button returns me to 1/500 sec for everything.

Since things work correctly for you, I must have a bad camera. Nuts! Guess it's time to contact the Pentax warranty department... :-(
I have absolutely the same problem as you. The problem appears only using old M lens. With the Kit lens everything is ok. Have you found the solution?
Maybe it is possible to "reset" the camera by pressing some hidden combination of buttons?
02-01-2013, 02:07 PM   #123
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I have just seen, that the shutter speed is changed only when you change the ISO. At 100 the speed is always 1/125, at 200 - 1/250, at 400 - 1/500 (as you, mspoon).
Hope, that it is not a factory defect. Tomorrow i will check this thing in the shop with another K-30.
02-02-2013, 02:54 AM   #124
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Probably, i found the solution. The green button works adequatly, when I short the seventh pin (the last from the lense holder pin and the first from the screw) to the bayonet. My M42 lens is not wide, so it doesn't cover the pins by its body. The adapter ring is also without the flat part, covering the pins ( I have the "original" one with "Pentax" and "Phillipines" words on it).
However even in this case the expo-bar in the viewfinder is not displayed.

In this case I have a two questions for everybody who are using the old lenses without any problems:
1) are the pins shorted in your system, when you use the old lenses? Sometime, the lens body are painted or just annodized aluminium, so the pins covering is not enough. The conductivity of the lens body is necessary too.
2) do you see the expo-bar, showing the "underexposity" or "overexposity" of the scene in the viewfinder after pressing the green button with the old lenses?

Thank you very much for the help!

02-02-2013, 08:56 AM   #125
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Older Pentax Lenses

Are there adapters available for Pentax Takumar 300mm F4 to use on my Nikon camera D300. I have a Pentax 50MM 1.2f also. Love these lenses. Wont to use them.
02-03-2013, 12:58 AM   #126
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From RioRico at

Here's what helped me out the most using my manual lenses...

Some tips on manual control and manual lenses:

* MFL's may have PK-A mount (with aperture-control contacts on the base); with PK-M mount (with just a mechanical aperture linkage); with simple PK mount (no aperture linkage); or in various modded or screwmounts. With an A-type lens, just set the camera to any Auto mode, set the aperture ring to A, and don't worry. With a simple PK or a modded lens or an adapted screwmount, set the camera to any Auto mode (it will default to Av) and spin the aperture ring for control. For manual control, or with any M-type (including K-type) lens, read on.

* Pentax K-type (they just say SMC on the front) and M-type lenses will only work wide-open if the camera is in any Auto mode. Set the camera to M mode, press the Green button, and the camera will mechanically stop-down the lens for metering and exposures. I often leave the mode dial to the setting just below M; on my K20D and your K5, that's TAv. On a Kr or Kx it's probably Av. But it's a handy position. To shoot stopped-down, quick-dial to M and hit the Green button. To shoot wide-open, dial back to Av and let the camera worry about the shutter speed.

* Manual exposure is handy with AF and A-type lenses as well as their predecessors. Auto exposures can vary depending on shifting light|shade qualities. I like to take a manual reading off a gray card or my hand or whatever. This reads incident (ambient) light, the light falling on the subject, not the light that variously reflects from the subject field.
02-03-2013, 12:12 PM   #127
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Instead of the green button you can also press the +/- button for metering
02-04-2013, 01:17 PM   #128
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Hanimex Lens

Dear all,

Wondering if anyone of you can help with this?

I have a Pentax K-x with 18-55mm lens. I also have from an old Pentax camera a Hanimex HMC 75-300mm lens which I would like to use on my K-x.
I have tried to fit to the camera but it looks as though the black flange is stopping it from fitting.

Does anyone know how to get this to work? I have tried removing the black flange but the camera would not fire then. Yes it was on Manual when I tested it.

See picture of lens mount attached.

Attached Images
02-06-2013, 02:21 PM   #129
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K30 and F lenses.

Having just started to use the new toy I found the How to use Manual &M42 lenses thread very useful indeed including the update for K30 Thanks
I have been trying to use two old K non auto which seem to be working very well but want to pass on a tip .
I found by trial and error that the magnification function on replay only works when the aperture ring is set to the mark between the smallest stop eg 4.5 and the next .I do not know what this indicated when used on a film slr but it is doing something on the K30.
02-23-2013, 12:24 PM   #130
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Can you revisit the adapter issue? The Pentax web store no longer sells the adapter, that link is dead.
The third party one you link (in the original main post) and recommend as good is the one sold at BH --- and looking there, it has comments saying it lacks a 'removal key' and will require carrying a screwdriver to get it back out of the K-mount. Is this just lack of explanation, or is there a better alternative these days?
02-23-2013, 01:19 PM   #131
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I have a K-r camera and recently bought the K-to-M42 adapter from a member here on the Pentax Forum (a great place to buy and sell to other Pentaxians). It is an old, original K-to-M42 (screw) mount adapter, nice and thin. Easy. Take your lens off the camera body. Screw the adapter into the hole. Mount the Takumar (or other M42/screw-mount) lens onto the adapter. Comes off as easy as it went on. No screwdriver needed.
03-12-2013, 11:15 AM   #132
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The online manual for the m42-pk adapter states "Do not use any non-Pentax screwmount or bayonet lenses before you have verified that they have no irregular protrusions on the rear."

The SMC Takumar 55mm f1.8 copy I have has a little pin that protrudes 2-3mm after installing it (by screwing into) into a m42-pk adapter that looks like the one pictured in the first post. The general opinion seems to be that there is nothing to fear using Takumar m42 lenses (with adapters) as is, but some posts indicate that not all Takumar screwmounts have that pin at the rear.

Apologies for asking what has likely been clarified elsewhere. Can the Super Multicoated Takumar 55mm f1.8 cause any grief if I use it (WITHOUT modification) with a flangeless M42-adapter? (I am not worried about the adapter as much as pin at the rear of the lens getting stuck).
03-12-2013, 07:05 PM   #133
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I have that very lens (bought from a member here) with that very pin and have no issues. In fact, that is my favorite lens; it gives me no grief whatsoever. I use the genuine Pentax M42 to K mount adapter that I bought right here from a member as well. Best two purchases I ever made.
03-12-2013, 07:43 PM   #134
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QuoteOriginally posted by timmijo Quote
I have that very lens (bought from a member here) with that very pin and have no issues. In fact, that is my favorite lens; it gives me no grief whatsoever. I use the genuine Pentax M42 to K mount adapter that I bought right here from a member as well. Best two purchases I ever made.
Thank you for responding. Can't wait to try it out. Indeed, the build quality of the lens is superb, even adjusting the focus ring is a pleasure. I've tried ( on a different camera system) a large number of MF lenses reputed to have excellent build...this Tak though is on a different level.

Despite trying I was unable to procure a original pentax adapter (not sure why pentax won't manufacture and stock them in volume), so settled for a copy which passes the look test.
03-14-2013, 12:17 PM   #135
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Keep trying. The genuines pop up here quite often and sometimes also on EBay. If all else fails, get one from B&H; make sure you go for the genuine Pentax K to M42 adapter. (I believe they are being designed and made from the same mold as the original ones but with a different metal these days—I prefer the old, original metal one that says Pentax and Japan on it.)

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