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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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08-14-2015, 09:13 AM   #286
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@semaca
QuoteQuote:
I don't know how much should I screw because of those contacts.
Can you explain what you mean?

If you do not screw the lens fully into the adapter, there is a different behaviour of original Pentax and 3rd party ones.

Without a lens attached, (only) the original one will stay loose. Screwing in a lens in (fully!) will force the adapter to press against the mount from the inside of the body. Otherwise you may adjust distance with LV, but shooting can put the lens to a slightly different position, and focus will be lost.

EDIT:
This behaviour of the original adapter is also the reason why you can't use these for staying permanently attached (and fixed) to each of your M42 lenses. Putting it on the body, the combination would stay loose.

You can do it with 3rd party adapters; but remove the screw prior to attaching it, otherwise you could be in serious trouble when trying to remove the lens. And test it carefully before making it a permanent solution, because of bad meeting of tolerances the set may still not come off, even with the screw removed.


Last edited by RKKS08; 08-14-2015 at 09:28 AM. Reason: Info added, typing
09-21-2015, 02:02 PM   #287
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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.
I have Super Takumar (screw-type) lenses that I use with my K-500. I set up my camera correctly; but, when I stop down using the green button, the display shows F-- for the aperture. Is this normal? Is the camera still reading the f-stop I have manually set on the lens ?

Thanks
09-21-2015, 02:29 PM - 1 Like   #288
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QuoteOriginally posted by mjtgent Quote
I have Super Takumar (screw-type) lenses that I use with my K-500. I set up my camera correctly; but, when I stop down using the green button, the display shows F-- for the aperture. Is this normal? Is the camera still reading the f-stop I have manually set on the lens ?

Thanks
It can't. Screw mounts have a different aperture lever. You must put the lens on manual with the auto/manual switch on the lens (or a/m) and stop down yourself (you will see the viewfinder get darker as you stop down, so focus first, stop down later.)
09-22-2015, 05:30 AM   #289
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QuoteOriginally posted by mjtgent Quote
I set up my camera correctly; but, when I stop down using the green button, the display shows F-- for the aperture.
All Pentax and Takumar lenses (and related third-party lenses) prior to the Pentax A mount lack the electrical contacts necessary to pass precise F-stop information to the camera. Even on film bodies with wide open metering, the Takumar SMC, K and M lenses only ever informed the camera how many stops from wide open they were set to (which is what the metering needed to know), not the exact aperture value. If the K mount were ever "un-crippled", the camera would need to be programmed with the widest stop whenever you switched it on, as it is programmed with focal length for shake-reduction today. IIRC the KA-mount lenses report their minimum aperture and the DSLR controls things relative to fully-stopped-down.

One of the things I'd be looking for in a future Pentax DSLR is firmware that would write that focal length into EXIF even when the SR is turned off. My K-5 currently doesn't do that.

10-31-2015, 02:07 AM   #290
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By Pentax K20D is pretty easy to use MF lenses & taking photos is almost quck as with AF. I found that "bug" in my photocamera accidentally.

When I put on my K20D Pentax M 50mm/f2 without adapter (!), I swich back from MF on AF (!!), than I hold shutter down & I moove focus ring to get the proper sharpness - when opbject is sharp I see a little light in viewfinder & than happens a mirracle: photocamera automaticly takes photo with MF lenses ... even a few of them if I want continuous shooting. It stops when I release the shutter or turn focus ring on lenses. With a little exercise it works realy quick. The same joke is with Pentax MF 150mm/f3,5 ... so taking photos is simple: by holding shutter down, I take photos with focus ring on lenses.

The main question: does Pentax K3 & K3 II have the same option/bug??
11-01-2015, 07:29 AM   #291
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That sounds like "Catch in Focus":

Catch-in-Focus Tutorial - Articles and Tips | PentaxForums.com
11-01-2015, 10:15 AM   #292
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Question. A number of posters to this thread have advised removing the screw and spring tab assembly that locks M42 to PK adapters in the camera body. Would machining an opening in the rear of the lens being mounted that would accommodate the body locking pin restore the lens lock security that removing the adapter spring forfeits?
11-22-2015, 12:59 AM   #293
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Avoiding auto iso is indeed necessary. My K-50 won't go into M mode unless I choose one single manual iso setting and the camera won't stop down the lens when metering with the green button or releasing the shutter. Using Auto ISO including a limited ISO range will leave the lens wide open.

11-22-2015, 06:00 AM   #294
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Strange, everything AUTO is cancelled when I put my K-5 in M including ISO. Should work the same on the K-50
12-20-2015, 03:36 PM   #295
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QuoteOriginally posted by First Poster Quote
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.

Something is a little confusing for me.


I made a bad experience with cheap extension tubes from China. Seems like the tubes' mount is not conductive -->> no camera metering.


But in case of M42 lenses, there's nothing in touch with the camera contacts, but the metering works just fine. Why?
12-20-2015, 06:41 PM   #296
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On the bodies where a conductive mount matters the auto aperture stop down lever will not actuate if the "data" pin is not shorted. Since the screw mount lens use a different system for auto stop down (or not at all) the lenses are closed down manually. This allows stop-down metering through the lens. With K-mount lenses you can only (without modification) stop the lens down via the lever.
01-02-2016, 08:18 PM   #297
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I've been through the various posts on this subject a number of times, but perhaps I need to read through them again. What I have found is this:

1. A Pentax OEM adapter is the best way to go if you can find one (just bought one on e-bay for $35, including shipping). I can install and remove it with my fingers. I had a Fotodiox and it nearly ruined a lens.
2. You can use the green button with K-mount lenses ONLY; I have been unsuccessful using it with M-42 mount lenses. Nothing happens.
3. The screw-mount (M-42) lens you're using has to be set to manual if it has a "manual"/"auto" setting, in order for the light meter to read it when you change the aperture.
4. On the K-50 (and others Pentax bodies with similar settings), you can use the TAV setting quite effectively with M-42 mount lenses. First, set it so it will only choose between ISO 100 and ISO 200 (or higher if you like). Then, when you choose the aperture on your M-42 lens, the camera will automatically choose shutter speed. This will produce consistent results—if you have limited the range of the ISO.
5. Because of #4 above, using M-42 mount lenses might be seen as an easier option than using a K-mount lens and having to remember to push the green button every time.
6. I haven't experimented with it yet, but I imagine AV mode would work with M-42 mounts too, probably easier than the TAV mode. I haven't seen either of these options mentioned by others. The Pentax/Ricoh website seems to indicate that the green button should work with M-42 mount lenses. It doesn't on my K-50.

I hope this is not redundant information. I'm just learning about Pentax cameras and loving every minute of the learning experience.

Last edited by fotograffiti; 01-02-2016 at 08:24 PM. Reason: Left out a few words
01-03-2016, 08:53 AM - 1 Like   #298
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The green button is programmable in different modes. in Av or TAv or P (when you put on an M42 lens the camera will automatically switch to Av mode even if it says P on the screen) it will simply reset your adjustments to standard P measuring. But it can be programmed to have different behaviour (as can the front and back dial).

M42 lenses were designed for a different mount. They lack an aperture lever or have an incompatible lever. So they can never be stopped down by K-mount camera's.

K- and M-lenses have a compatible lever, but modern dslr's need an electronic contact for aperture communications, so the camera can set the aperture. Old slr's could measure the aperture by the position (or the pressure?) of the aperture lever, so they would know the aperture set on the ring. dlrs can no longer do that, hence the aperture needs to be stopped down for measurement.

Maybe Pentax could add a special Av mode in which you can set the corresponding aperture on the ring to the camera yourself (instead of showing "--"). But that would arguably be more work than the green button method, but it would probably be more intuitive to use.
01-03-2016, 01:21 PM   #299
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The green button may not work on some bodies unless the "data" pin on the mount is shorted. Firmware revision may also be a factor. I believe the K30/K50 are among those that behave like this.
01-03-2016, 03:27 PM   #300
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@fotograffiti

To your 6 points:

1. It is, but there are 2 exceptions from this rule.

1a) If you own a lot of M42 lenses and do often switch lenses, the screw mount is unconvenient. There is a reason all main camera brands changed to bayonets in the sixties and seventies. But leaving one adapter on every lens does not make sense with the OEM adapter. This one fixes the lens on the body by pressing the adapter FROM THE INSIDE against the body mount. So this adapter always stays on the body when you remove the lens. If you remove the spring from an 3rd party adapter (and smooth sharp edges a bit), these adapters can do the trick. You may have to use a thin shim between lens and adapter if the adapter never comes off together with the lens. If the shim is too thick, the lens will be to loose; and the diameter of the shim should not be bigger than of the adapter, otherwise you may loose infinity.

1b) If you don't want to do surgery on M42 lenses with auto diaphragm - but no auto/man switch - you have to use a specially flanged adapter. This will set an auto M42 lens to manual. The Kipon brand is best known.

2. That's correct. Green button measurement uses the aperture actuator for closing the aperture to the set value. But with M42 lenses, there is no lever which it could move.

3. Yes.

4. No comment. My Pentaxes don't offer TAV (and if, I doubt whether I would use it).

5. With consistent light, in many cases you would need the Green Button only for the first shot. In M mode, the set value will not change for all the next shots.

6. AV is the way to go with M42 lenses. TAV includes AV, is a Pentax special, and was introduced only with the K20D. And about Green Button with M42 lenses: no, see point #2.

---------- Post added 03-01-16 at 23:37 ----------

QuoteOriginally posted by Not a Number Quote
The green button may not work on some bodies unless the "data" pin on the mount is shorted. Firmware revision may also be a factor. I believe the K30/K50 are among those that behave like this.
@Not a Number
Isn't this true only for pre A 3rd party lenses with an anodized mount ?
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