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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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04-29-2012, 03:56 PM   #91
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I see, thank you! It does not bother me, everything is doing fine
Thanks a lot!

05-20-2012, 02:37 PM   #92
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THANK YOU FOR POSTING THIS!!! While digging through a box of unused camera 'stuff' a few months ago, I came across two manual prime lenses that had belonged to my father and eventually became mine. They both date from the mid/late 1970s, and though the original 35mm SLR Pentax camera is long gone, I had used them extensively on my last film camera, especially with my macro lens set (which is also the same age). But when I got my K-5 last year, the <bleeping> thing didn't want to fire when I put on these lenses. I thought I was going to end up selling these gems on eBay. Now? Back to my macro work!! YAY!
05-20-2012, 05:41 PM   #93
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The M42-K converter

I just got two more adapters M42-K necessary to use the Takumars screw mount lenses on the DSLRs. The new genuine adapters cost $23 each. They are exactly the same as before with one exception: they added the word PHILLIPINES, as of made in Philippines.

Here is how it looks now:



Last edited by Pepe Guitarra; 05-22-2012 at 08:48 PM. Reason: Add photo
06-12-2012, 03:38 AM   #94
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Great guide!

I have read through the instructions, experimented a bit and understand the principles. The issue I might have is that I picked up an m85 f2, but the aperture ring, despite working perfectly, no longer has stops or detents for the settings. In other words, it spins freely.

I'm assuming that if I try to stop down to meter, the ring will spin and change the aperture setting as the camera attempts to figure out where it's set.

What other ways can I shoot using this lens to avoid issues with the free-spinning ring? Note that I don't have the lens yet, so I don't know the behavior of it on the K-5. I'm guessing just plain M or A mode, then using the exposure meter to handle it, correct? But then will the aperture actuator continue to move the blades when the shutter is actuated?

06-12-2012, 11:34 AM   #95
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QuoteOriginally posted by snake Quote
Great guide!

I have read through the instructions, experimented a bit and understand the principles. The issue I might have is that I picked up an m85 f2, but the aperture ring, despite working perfectly, no longer has stops or detents for the settings. In other words, it spins freely.
This just means someone opened up the lens for unknown repair and during the process, managed to lose either the detent spring or the ball. Define 'spin freely': There is no detent stops so the aperture ring turns without clicking at half stop marks or does it literally turn if you happen to breathe on the lens or shake or tilt the lens?

QuoteQuote:
I'm assuming that if I try to stop down to meter, the ring will spin and change the aperture setting as the camera attempts to figure out where it's set.

What other ways can I shoot using this lens to avoid issues with the free-spinning ring? Note that I don't have the lens yet, so I don't know the behavior of it on the K-5. I'm guessing just plain M or A mode, then using the exposure meter to handle it, correct? But then will the aperture actuator continue to move the blades when the shutter is actuated?
I don't think the aperture actuator can affect the movement of the diaphragm, the detent stops are for the user's convenience to mentally keep track of the aperture value used for a particular shot. You will be shooting in M mode, pressing the green button to meter - with the detent ball or spring missing, you have infinite diaphragm control instead of mere half stop increment.
06-12-2012, 12:12 PM   #96
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I don't have the lens yet, but it was described as the ring working perfectly, with the exception that it doesn't click or lock at stops. This leads me to believe that it was likely modified for video use. I will have to see how accurate the description is when I get it, but it's listed as perfect, outside of the fact that the ring doesn't lock at the stops. For video, that's an advantage for me, since I do play with aperture during shooting and having the clicks are a bit obtrusive.

Ok, thanks for part two.

I'm eager to see if this lens works as well as its reported to and if there are complications with the ring not having detents.
06-13-2012, 04:53 AM   #97
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Ok, I got the lens, it's in very nice shape. However, I will explicitly confirm that when using stop-down/green button metering, the aperture ring does drift slightly, but only a half stop from f2-f2.4 or so.

I'm going to look through some more threads, but it is somewhat more complicated than my Olympus E510, which was extremely straight-forward with manual lenses. Simply put on, watch the ev meter, then shoot. So it seems being able to simply set around the EV meter is a bit of a luxury there.

The other issue I'm having on the K-5 is that any aperture setting smaller than f2 induces massive overexposure.

I'll continue on and try aperture priority, which would likely cure the overexposure and also allow auto ISO.

The main problem is that the aperture is held open by the aperture actuator in the body, which is something I'm not used to, so how do I overcome this wihtout stop-down metering?

Any tips would be handy.

EDIT: Argh. Aperture priority doesn't produce automatic shutter speed changes with auto ISO.

Last edited by snake; 06-13-2012 at 05:03 AM.
06-13-2012, 07:43 AM - 1 Like   #98
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Snake, one option is to drill a second locking hole in your lens, so it will lock halfway into the mount, and thus the aperture lever won't be engaged by the camera's actuator. So turning the aperture ring on the lens will result in an immediate darkening of the viewfinder.
This works in M and Av mode (but obviously in Av mode aperture won't be controlled by the camera!).

A quick try can be made by just inserting the lens into the mount, without turning it full way. Try to put the lens' focus mark halfway between the mount's red dot and the 12 o'clock position.

06-21-2012, 07:35 PM   #99
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Metering with the Green Button vs. Metering with the Optical Preview on the K5

Hi colleagues,
I noticed something happening when I use my K5 with a bayonet mount (K, M type) lens: In the Manual mode M, I set my ISO, my exposure, and manually set my aperture, then focus and stop down with the green button. Result: Nice photo, perfectly well balanced, etc. Sometimes, not the effect that I wanted, but well balanced. I notice that when I stop down with the green button, the camera does meter, but it also changes the exposure, JUST LIKE IN AV PRIORITY MODE.
When in manual mode M, I set my ISO, exposure, and manually set the aperture, but stop down the lens with the optical preview, the camera does meter and stops down the lens, but it does not change my aperture. In general, I get what I set the camera for.

In conclusion, if you stop down with the green button, you get an AV priority shot. I checked the K5 manual and it does say that the camera will automatically change the exposure. If you stop with the optical preview, then you get a true manual behavior.

Is this what everyone noticed? Am I wrong? I have not tested this theory on the Kx. I am not sure where the optical preview is. I guess is assigned to the green button, go figure.

I expect your comments.
06-27-2012, 07:32 AM - 1 Like   #100
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Diacouture has the solution but does not emphasise it enough.
Mount your lens fully and then back it out about 10 degrees and then just use it in stopped down metering mode.
It sure beats all that green button stuff.
The viewfinder gets a little darker if you stop down a lot and that causes focus confirmation to be more difficult but just twist the aperture ring wide open to focus before returning to the desired aperture.
This enables you to use all your Pentax and Takumar lenses the same way.
A similar technique is to lift the camera mount and short out the furthest data terminal (going anti clockwise) with a sliver of foil but I found the previous suggested method more consistent over all lenses.
08-16-2012, 01:32 PM   #101
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Thank you Adam and others! Wondered how to use the M lens on my K-5.. 2 seconds of searching got me to this article & it works perfectly.
11-06-2012, 03:29 PM   #102
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I too would like to emphasise what dlacouture and Kevcol say about using K and M lenses in AV mode.

I have two K lenses where the aperture lever would not return under spring pressure, largely due to oily blades and weak springs. The aperture rings however did open and close the irises. After two unsuccessful dismantling and cleans I resorted to the tried and tested, but painful, cutting off the aperture levers, thus turning the lenses into M42 type operation and full use of AV mode. I was so pleased with the results that I contemplated cutting a few healthy 'M's as well......and I'm so glad that I found this article first. Thank you both

I will admit to drilling lock holes in the mounts of eight M and K lenses but mounts are easily changeable if required. Severed aperture levers are not.

Oh, and a couple of Tamron Adaptall mounts and a couple of Vivitars and a Chinon got the treatment too. All working very well. No more Green Button. Yes

Thank you again

Phil P

Last edited by f8orbust; 11-06-2012 at 03:59 PM.
11-24-2012, 08:02 PM   #103
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QuoteOriginally posted by joe.penn Quote
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:
...
5: Scroll Select 50mm
...
Stupid/simple question: when selecting the focal length, must be multiplied by crop factor (1.5) or just the nominal value? For example, on a 50 mm should I select 75? A bit confused here
Thanks,
Sandu
11-24-2012, 08:09 PM   #104
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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 new 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-30, K-5, 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. You can order it directly from Pentax for $30.95. 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 adater.

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 (#21 on the K-7, #27 on the K-5), 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.

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:

  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).

Click here
if you found this article helpful!
I was glad for your post. However I have a K5 and I am using a Tamron 30-80 adptall lens that i had with my ME super. The manual focusing is good, pictures are sharp but the exposure is off. Auto correct on the computer fixes it but can it be done before shooting. When you press the shutter button you see F-- in the viewfinder. Does this mean that it is underexposed automatically?
11-24-2012, 08:49 PM   #105
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QuoteOriginally posted by BSandu Quote
Stupid/simple question: when selecting the focal length, must be multiplied by crop factor (1.5) or just the nominal value? For example, on a 50 mm should I select 75? A bit confused here
Thanks,
Sandu
The simple way of going about this is: forget about crop or not crop factor. If the lens is 50mm, then select 50mm. The camera will ask you for the focal length only to make sure it will operated the vibration control properly for that length. THat is it. The 1.5 factor something else.
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