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-1 series, KP, K-3 series, K-70, K-S2, K-S1, 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. 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.

At startup, if your camera asks you for the focal length, enter the actual focal length as labeled on the lens. This will ensure optimal Shake Reduction performance. For zooms, you can use the lower end of the zoom range (this ensures that there will be no over-compensation), or the focal length that you shoot at most often.

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). Note your lens will not stop down until step 5.
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" (older bodies may use the Av 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.

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[sourcenemy]

I downloaded the K50 manual (English). See page 114 on setting Depth of Field preview to the RAW/FX+ button.

Let's review:

What M42 adapter are you using? Is it a genuine Pentax adapter, a 3rd party copy of the Pentax adapter or a 3rd party adapter with a flange? If it is a flanged adapter is it bare metal or painted/coated/anodized (usually black)? This may make a difference as the flangeless adapters or painted flanged adapters do not short the contact pins on the camera body. On some bodies or perhaps firmware versions the green button and DOF preview behaves differently if the contacts are shorted or not.

For manual exposure camera should be set to Manual, aperture ring enabled, ISO anything but AUTO, green button in M or Tav set to Tv shift, DOF preview to optical on the RAW button. Liveview disabled for these examples.

M42 lenses:
Turn on the camera, set to Manual mode. Lens should be wide open - if the lens has manual/auto switch moving the switch so the word "auto" appears will open the iris all the way no matter what the f-stop is set to on the ring. If it is set so the word "man" is visible or the lens doe not have a switch set ring to the largest aperture. Half press the shutter button to turn on the meter, focus confirmation and shake reduction. Compose and focus. Set the f-stop you want to use. If an auto lens slide the switch so "auto" is visible. The lens should now be stopped down. Check composition - note focus confirmation may not work at the point depending on the f-stop. Press the green button - the camera will measure the light coming through the stop-down lens and set the appropriate shutter speed. Adjust the exposure with the edial or aperture ring (this is mostly a matter of experience). Take your exposure.

K-mount lenses - non-A with bare metal mounts:
Turn on the camera, set to Manual mode. Half press the shutter. Focus and compose. Set the f-stop - lens should remain wide open regardless of f-stop setting unless it has been modified or damaged. Press the green button - lens should should stop down briefly, the camera measures the light coming through the stop-down lens and set the appropriate shutter speed. Adjust exposure with either the aperture ring or the shutter speed edial.

So really the only procedural difference between M42 and non-A K mount lenses is that you have to manually stop down M42 lenses.

But as noted before the green button or DOF may behave differently on some bodies depending on if the contacts are shorted or not.

This is entirely up to you at the risk of getting dust on the sensor - try pressing the green button with no lens attached. Does it behave the same as with the M42 lens (assuming non-flanged adapter) or a it does with your K-mount lens? Another way would be to put some non-conducting tape or a slip of paper between the contacts on the lens and camera body mount.

What happens if you use Liveview?

First of I LOVE YOU Not A Number!! waiting for you beginners guid into photography with Pentax

and i use a 3rd party copy of the Pentax adapter for my m42 lenses, and my RAW/FX + button is now set for Optical Preview

but atm im try to get a hang of my new Pentax-M zoom 40-80mm macro lense and im thinking hard about wether to keep my K-50 or sell it and get a Canon 7D housing instead...the thing is its my GF thats the real photographer in this house
and shes on a Canon 5D mk II but needs a faster backup like the 7D and since im totaly lost with all this i figured i'd get a 7D that she can use when needed and since im a total noob i might as well learn the Canon meny and i would keep my Pentax-M and m42 lenses to use on the 7D with adapters.... but at the same time im thinking of selling this one and save up the last and get me a K-3 so i can get a battery grip 'couse this small housing is realy starting to bug the hell out of me and i need a external Mic for filming...

---------- Post added 08-22-14 at 08:37 AM ----------

hmm i just mounted a m42 lenses to check out DOF on my RAW/FX button but when i press it the manual says the viewfinder should go empty while pressing the button (for easier view i guess?)
and when i release the button it goes back to normal but when i press the button the info lines at the bottom dont go away it just starts to flicker as long as i'm pressing the button???

[Not a Number]

hmm i just mounted a m42 lenses to check out DOF on my RAW/FX button but when i press it the manual says the viewfinder should go empty while pressing the button (for easier view i guess?)
and when i release the button it goes back to normal but when i press the button the info lines at the bottom dont go away it just starts to flicker as long as i'm pressing the button???

I hope you have removed the spring clip or have the adapter that SRB in the UK sells. Otherwise you may end up with the dreaded screw mount lens jammed on the body.

Since I don't have a K50 I couldn't tell you if this is normal behavior or not. On my K-10D the display stays off in optical preview with "A" lenses and displays the exposure bars, shutter speed and F- - for the f-stop on non-A and screwmount lenses. The "F- -" will blink if "use aperture ring" is not set. My guess is that it flickers on the K-50 as a warning that a screwmount or no lens is attached (no electrical connection on the mount). It could be a reminder that you have to stop-down manually for DOF preview. Since the K50 doesn't use the exposure bars during optical preview with non-A lenses it would do nothing with screwmount lenses any way. You can check the DOF any time you stop down the lens.

You may want to post on the K30 & K50 sub-forum and see if this is normal.

Does the green button still behave as if it was doing an digital DOF preview with the K-Mount lens?

You would use the same stop-down metering methods on a Canon with K-mount and M42 lenses. Be aware too the that auto stop-down lever on K-mount lenses may hit the mirror on some Canon bodies. The solution is to either cut down the mirror or modify the lever on the lens. The later can many times be done in a reversible manner but most often Canon owners mutilate the lens by cutting off the lever.

[sourcenemy]

the spring clip is off couse it started to act up straight from the start and didnt wanna end up with it coming off inside the housing and no its not suppose to act like that with the flickering not if you belive the manual since that says when set up for optical preview and pressing the RAW/FX+ button all info thats shown normally should turn off so its blank when you try to check your DOF... will try green button later when im changing back to a K-mount, atm with m42 attached it just changes the shutter speed (top left corner next to MF? and it still seems to be setting to a predetermined level depending on what ISO is set to like ISO 400 it sets 1/500 no mater what light is availiable or ISO 1600 gives 1/2000 as value....

---------- Post added 08-22-14 at 06:40 PM ----------

ohh the flickering is actually flickering at a uneven rate more like the button has a small short in it its not a steady blinking like how F-- blinks when you havent set for using aperture ring...

[D1N0]

Optical preview doesn't work with m42 lenses, because of the lack of an appropriate aperture lever. You can manually close the aperture though. Which m42 lenses are you using?

[Not a Number]

The manuals are not definitive. For instance there is no mention of using the exposure bars during optical preview. Or even the settings for using older lenses for that matter. The settings are found on the support website which still doesn't mention the exposure bars.

What are your Program Line (P-Line) settings? This can affect what shutter speeds the camera will set, however it sounds like these are way out of line. There have been a few other threads on manual focus green button issues on the k50 and k500 before. You may want to search and review those threads.

What firmware version do you have? Hold down the "menu" button when you turn the camera on to see what version is installed.

If you do update the firmware make sure your battery is fully charged first and to read carefully the posts on the update procedure.

[GUB]

I downloaded the K50 manual (English). See page 114 on setting Depth of Field preview to the RAW/FX+ button.

Let's review:

What M42 adapter are you using? Is it a genuine Pentax adapter, a 3rd party copy of the Pentax adapter or a 3rd party adapter with a flange? If it is a flanged adapter is it bare metal or painted/coated/anodized (usually black)? This may make a difference as the flangeless adapters or painted flanged adapters do not short the contact pins on the camera body. On some bodies or perhaps firmware versions the green button and DOF preview behaves differently if the contacts are shorted or not.

For manual exposure camera should be set to Manual, aperture ring enabled, ISO anything but AUTO, green button in M or Tav set to Tv shift, DOF preview to optical on the RAW button. Liveview disabled for these examples.

M42 lenses:
Turn on the camera, set to Manual mode. Lens should be wide open - if the lens has manual/auto switch moving the switch so the word "auto" appears will open the iris all the way no matter what the f-stop is set to on the ring. If it is set so the word "man" is visible or the lens doe not have a switch set ring to the largest aperture. Half press the shutter button to turn on the meter, focus confirmation and shake reduction. Compose and focus. Set the f-stop you want to use. If an auto lens slide the switch so "auto" is visible. The lens should now be stopped down. Check composition - note focus confirmation may not work at the point depending on the f-stop. Press the green button - the camera will measure the light coming through the stop-down lens and set the appropriate shutter speed. Adjust the exposure with the edial or aperture ring (this is mostly a matter of experience). Take your exposure.

K-mount lenses - non-A with bare metal mounts:
Turn on the camera, set to Manual mode. Half press the shutter. Focus and compose. Set the f-stop - lens should remain wide open regardless of f-stop setting unless it has been modified or damaged. Press the green button - lens should should stop down briefly, the camera measures the light coming through the stop-down lens and set the appropriate shutter speed. Adjust exposure with either the aperture ring or the shutter speed edial.

So really the only procedural difference between M42 and non-A K mount lenses is that you have to manually stop down M42 lenses.

But as noted before the green button or DOF may behave differently on some bodies depending on if the contacts are shorted or not.

This is entirely up to you at the risk of getting dust on the sensor - try pressing the green button with no lens attached. Does it behave the same as with the M42 lens (assuming non-flanged adapter) or a it does with your K-mount lens? Another way would be to put some non-conducting tape or a slip of paper between the contacts on the lens and camera body mount.

What happens if you use Liveview?

Good stuff but a couple of things. I have a tendency to hold the camera away from my face when pressing the green button(thanks to big fingers!!). This allows light to pour in the viewfinder giving innaccurate settings. So thumb over the viewfinder.
And M series lens due to their age often have sluggish stop down . To take a pic via the green button involves the stop down process happening twice--- another source of variable results. Remember the body does not force the lens to stop down but rather moves a lever away allowing the lens to stop down under the power(or lack of) of its own spring. That is why I use the "not totally on" approach that I described in post 213.

[Lowell Goudge]

after seeing yet another post about metering inaccuracies on K mount (non A) lenses, it occurred to me that i have never posted this chart here.

Metering with manual aperture lenses is not 100% linear, and while many times it is "good enough" it has its faults. The chart below was made using a K50/1.4 lens, and shots were taken with the different cameras and configurations i own.(plus a little help from other forum members). The process was to use manual mode and green button metering to set exposure, shooting a uniformly lit wall. I have used also paved roads, sidewalks and both interior artificially lit surfaces as well as outside concrete block walls, the result is not changed.

You shoot a shot at each manual aperture click, using green button for metering, and then in your photo editor, measure the greyscale value of the frame (i used a 10% centrally located selection but not all editors allow for greyscale value to be calculated on a selection) the result is below when plotted against aperture. All shots were done in JPEG with neutral contrast and saturation. Note each 45 greyscale is equal to 1 stop between the range of about 25-225.

I recommend serious legacy lens shooters map out each lens and body they own.

[GUB]

after seeing yet another post about metering inaccuracies on K mount (non A) lenses, it occurred to me that i have never posted this chart here.

Metering with manual aperture lenses is not 100% linear, and while many times it is "good enough" it has its faults. The chart below was made using a K50/1.4 lens, and shots were taken with the different cameras and configurations i own.(plus a little help from other forum members). The process was to use manual mode and green button metering to set exposure, shooting a uniformly lit wall. I have used also paved roads, sidewalks and both interior artificially lit surfaces as well as outside concrete block walls, the result is not changed.

You shoot a shot at each manual aperture click, using green button for metering, and then in your photo editor, measure the greyscale value of the frame (i used a 10% centrally located selection but not all editors allow for greyscale value to be calculated on a selection) the result is below when plotted against aperture. All shots were done in JPEG with neutral contrast and saturation. Note each 45 greyscale is equal to 1 stop between the range of about 25-225.

I recommend serious legacy lens shooters map out each lens and body they own.

Trying to understand your graph and not sure about greyscale nomenclature. So taking the cyan example of the K10 does this mean that at f8 your lens was underexposing by about 2 stops in comparison to wide open? And the ideal would be a straight horizontal line?

[waterfall]

I have an A 135 that works great on A. Can I use it on aperture ring to get some practice in stop down metering to see if I am capable of using K and M mount lenses efficiently? Will using the A135 this way mimic accurately what I would have to do with K and M lenses?

[Pepe Guitarra]

I have an A 135 that works great on A. Can I use it on aperture ring to get some practice in stop down metering to see if I am capable of using K and M mount lenses efficiently? Will using the A135 this way mimic accurately what I would have to do with K and M lenses?

Sure. Most of my lenses do not have th e A, and the green button becomes second nature. For example the pentax K 28/2 is probably the best lense ever, it has to be green-buttoned.

[waterfall]

Sure. Most of my lenses do not have th e A, and the green button becomes second nature. For example the pentax K 28/2 is probably the best lense ever, it has to be green-buttoned.

Thanks very much. Time for me to practice!

[Lowell Goudge]

Trying to understand your graph and not sure about greyscale nomenclature. So taking the cyan example of the K10 does this mean that at f8 your lens was underexposing by about 2 stops in comparison to wide open? And the ideal would be a straight horizontal line?

You have it backwards. It over exposes not under exposes. When you do a histogram, white is 255, black is zero, and normal exposure is about 128. Look at the A50/1.2 which is a flat line through the middle. What you see there is errors wide open and at minimum aperture but the remainder is perfectly flat.

[GUB]

You have it backwards. It over exposes not under exposes. When you do a histogram, white is 255, black is zero, and normal exposure is about 128. Look at the A50/1.2 which is a flat line through the middle. What you see there is errors wide open and at minimum aperture but the remainder is perfectly flat.

So then it is quite likely a viscous aperture mechanism?
Have you repeated the test at different ambient temperatures.?
Do the shutter speeds indicate that the body was responding to the stop change appropriately?
It is this type of lens behaviour that makes me find that unmounting the lens back about 7mm and using AV gives far more consistent results.

[Lowell Goudge]

So then it is quite likely a viscous aperture mechanism?
Have you repeated the test at different ambient temperatures.?
Do the shutter speeds indicate that the body was responding to the stop change appropriately?
It is this type of lens behaviour that makes me find that unmounting the lens back about 7mm and using AV gives far more consistent results.

For A lenses it is a problematic aperture because the line should be flat. But for manual aperture lenses, it is truly an issue I believe with the amount of scatter back off the focusing screen, as a function of aperture. I can't prove it of course but the results are consistent with all manual lenses

Shooting AV mode by backing a K mount off is not a solution as the error is there all the time, it is metering not aperture control that is the issue.

[GUB]

For A lenses it is a problematic aperture because the line should be flat. But for manual aperture lenses, it is truly an issue I believe with the amount of scatter back off the focusing screen, as a function of aperture. I can't prove it of course but the results are consistent with all manual lenses

Shooting AV mode by backing a K mount off is not a solution as the error is there all the time, it is metering not aperture control that is the issue.

Thanks for the info Lowell. I see there is quite a few scattered threads about it. Is there a definitive thread you can direct me to?
Thought I would have a bit of an experiment with a pentaxM 50mm f1.7.
Took a range of images comparing LV vs Optical viewfinder metering and comparing using the green button vs my unmounting the lens trick.
I cut and pasted sections of the images to make the chart which I think is about as graphical as a graph.
the exposures range from about 90 to 163 on the greyscale image. (if I am reading things right)
So would that be about a 2 stop range?
The results were not very repeatable. (I went back and did the repeats a bit later)
Interesting that Live View with the lens backed off and set on AV was easily the most consistent.