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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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02-06-2015, 07:51 AM   #271
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Big thanks for this great guide. Would never solved it by myself.

Stupid question:
I don't use the green button with "modern" lenses, then I don't need to reprogram it when swapping because
the green button settings doesn't affect any other settings, right?

02-06-2015, 07:55 AM - 1 Like   #272
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The green button resets your value's to P-mode in other modes.
02-07-2015, 01:37 AM   #273
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Thanks.
02-07-2015, 05:19 AM   #274
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When starting the K-30, with a 105mm Tamron adaptall mounted, my closet choice is 100mm focal length.

Do anyone know if that might be an issue?

.


Last edited by Stefan Jr; 02-07-2015 at 05:32 AM. Reason: grama
02-07-2015, 05:31 AM - 1 Like   #275
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I see in your profile you have a Tamron 105. I have a Tamron 90 and was told when the camera asks for FL to use one below what it actually is. In other words, on your Tamron you would use 100mm. And no, there isn't any other issues.

Last edited by photolady95; 02-07-2015 at 05:38 AM.
02-07-2015, 07:45 AM   #276
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Photolady95,
Great - thanks for the info. Very appreciated!
I was a bit worried it'd affect the metering during focus confirmation. Since I have no clue about those "technical" issues.

Last edited by Stefan Jr; 02-07-2015 at 08:06 AM.
03-13-2015, 10:05 AM   #277
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QuoteOriginally posted by emergo Quote
is there any problem with installing the adapter to the lens and changing lenses normally? that is, having several M42s each with their own adapters that you leave on them full time?
Given the low cost of the adapters, I would prefer to leave them on the lens and use the k-mount lens cap on the rear of the lens.
03-13-2015, 10:20 AM   #278
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^^ You can't remove the lens with the original adapter, without unscrewing it. You could get cheap third party adapters and remove the locking spring (which is advisable anyway because they tend to get stuck) Then the lens will just come of with the adapter attached to it. Sometimes the fit will be very tight, so it is hard to screw the lens with adapter on the camera and to take it of. You can resolve that by putting some sello tape under the adapterring on the lens flange.

03-14-2015, 05:01 AM   #279
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I just took the K3 and today I did a little test. Just a few photos, but the result was really bad comparing it when I used the M42 lenses on my older Nikon. I did all the setting on the camera, used focus confirmation or live view with focus peaking, but the image is blurry no matter the distance.
The top image is from a Takumar 50mm f/1.4 (very sharp until now), the bottom one is done with 18-35 at 50mm. 100% crop. I know the WB is not the same. I tried with SR on and off.
I don't know how much should I screw because of those contacts. The adapter is the original one.


03-14-2015, 06:28 AM   #280
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The same aperture for both pictures?
03-14-2015, 08:41 AM   #281
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DSLR Cameras with M42 Mount

Are there any DSLR cameras on the market which have the M42 mount on the body, such that one doesn't need to have any sort of adapter? Thank you.
03-14-2015, 08:59 AM   #282
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QuoteOriginally posted by Bill C. Quote
Are there any DSLR cameras on the market which have the M42 mount on the body, such that one doesn't need to have any sort of adapter? Thank you.
Nope there aren't. But the m42 adapter effectively makes a Pentax body into a m42 mount body. Just glue it in .

---------- Post added 14-03-15 at 18:01 ----------

QuoteOriginally posted by semaca Quote
I just took the K3 and today I did a little test. Just a few photos, but the result was really bad comparing it when I used the M42 lenses on my older Nikon. I did all the setting on the camera, used focus confirmation or live view with focus peaking, but the image is blurry no matter the distance.
The top image is from a Takumar 50mm f/1.4 (very sharp until now), the bottom one is done with 18-35 at 50mm. 100% crop. I know the WB is not the same. I tried with SR on and off.
I don't know how much should I screw because of those contacts. The adapter is the original one.

It's better make a separate thread for this.
03-14-2015, 01:11 PM   #283
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The sticks in the foreground are more in focus relatively speaking than the building.
Are you sure you are not using a noninfinity adapter. It has a flange compared to the image in the sticky at the top
03-14-2015, 01:23 PM   #284
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QuoteOriginally posted by GUB Quote
The sticks in the foreground are more in focus relatively speaking than the building.
Are you sure you are not using a noninfinity adapter. It has a flange compared to the image in the sticky at the top
The adapter is just like the one on the first page of this thread (Asahi). I will do another test with different aperture and focusing distance and write everything on a paper
06-26-2015, 02:47 AM   #285
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K-S1 makes things easier

The K-S1 makes the use of M lenses a little easier.

1. On the dial ring it will illuminate the allowed capture modes (Av, M and Effect, (Effect is really Av too)). So if you have mounted a M lens then only this 3 positions will have a green light.
2. Setting the green button function in M/TAv mode is not needed. In the mode PLINE as well as TvShift you will get the behaviour of TvShift. So default of PLINE is OK.
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