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03-08-2010, 02:43 AM   #1
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Lens mount question

Hi, i got a K7 on order and need to ask a totally noob question.

I'm getting some lenses on ebay and I see some different lens mounts and I'm having trouble finding out if I can use them

I'm seeing K mount lenses are all good but there are different types of K mount apparently. Also what about screw and bayonet type mounts? Can I only use one of these or both? If I need a converter, what do you recommend?

If someone could post a list of lens mount types that I can use straight away and maybe a list of types I would need a converter for I would be most appreciative.

Again, sorry for the noob question.

03-08-2010, 05:17 AM   #2
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Any lens for a Pentax K-mount will work without adaptor. Be aware of the Ricoh pin issue (I think it's called KR mount); do some research here on the forum.

All other lenses basically require an adaptor of some kind; I did read about a Nikon lens that seems to fit, but consider it exceptions.

M42 screwmount lenses can be used with e.g. PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet). I know of at least one other screwmount (M39) and there are probably others. If a sale only states screwmount, be careful as it might not be M42 and you need another adaptor.
Again do some research here on the forum for adaptor or adapter.

There are 3rd party adaptors as well. There are some bad experiences with them and there are good experiences with them; your research will reveal it. As I don't like to take risks with something expensive like a camera, I opted for the original Pentax one.

Also check out the lens review section for info on lenses.
03-08-2010, 08:19 AM   #3
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QuoteOriginally posted by sterretje Quote
Any lens for a Pentax K-mount will work without adaptor. Be aware of the Ricoh pin issue (I think it's called KR mount); do some research here on the forum.

All other lenses basically require an adaptor of some kind; I did read about a Nikon lens that seems to fit, but consider it exceptions.

M42 screwmount lenses can be used with e.g. PentaxWebstore Mount Adapter K(35m m Screwmount to Bayonet). I know of at least one other screwmount (M39) and there are probably others. If a sale only states screwmount, be careful as it might not be M42 and you need another adaptor.
Again do some research here on the forum for adaptor or adapter.

There are 3rd party adaptors as well. There are some bad experiences with them and there are good experiences with them; your research will reveal it. As I don't like to take risks with something expensive like a camera, I opted for the original Pentax one.

Also check out the lens review section for info on lenses.
Adapters can also be had to adapt M39 lenses to M42, so they can be adapted to K mount. Be aware that some lenses (aftermarket) use a T mount which requires a different adapter. A lot of the mirror lenses, the cheapo 2000mm type lenses, fall into this category. It's important to note because the thread Looks like the M42. Many ebay sellers don't know the difference. This is an example of a T mount lens. Some older vivitar lenses use a T-4 mount that I Think is unique to that company (whoever actually made them).

03-08-2010, 10:10 AM   #4
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Pentax K-mount lenses will all mount and work. The oldest K-mount lenses work only in M mode with stop-down metering. Lenses with an A position on the aperture ring allow the other modes to work and include other camera features. Lenses with autofocus are fully compatible. Pentax produced lenses for CCTV and medium-format cameras that aren't K-mount, but aren't too common either. They are well-labeled.

Other brands have followed the K-mount design, with a few problem lenses. Ricoh, Sears and a few other inexpensive brand lenses have a pin that can lock in the slot for the screwdrive AF. The pin can be easily disabled or removed if you know about it ahead of time. Some versions of this pin work without trouble. Some lenses have an extended light shield, common on older Vivitars, that interfere with lens mounting. The shield is easily removed and/or modified. And Sigma lenses sometimes do not auto-focus because Sigma did not license the technology from Pentax. I think that's about it for K-mount lenses that might cause problems.

The K-mount was designed with similar specs to the M42 mount, so M42 mount lenses work well with an adapter as described above. Using an adapter limits your camera's modes, similar to an older K-mount lens. There are many M42 lens manufacturers and many variations on the mount, with a few designs that might need some assistance before they're usable. A complete list is impossible. Takumar M42 lenses have no issues, though again, there are a handful of Takumars designed for 6x7 cameras or very old camera systems. (Usually these sell for like six times the price you'd expect.) The main feature to look for on an M42 lens is a switch for the aperture, usually labeled AUTO/MAN or A/M. Otherwise you may have to modify the lens yourself.

T-mounts are the next most common lenses, typically really long focal lengths, microscope adapters or accessories. That's covered above too. The T-mount is simple and the lenses that use it are not very complex either. A poorly machined T-mount can be mounted incorrectly and get stuck, so use care when mounting.

03-08-2010, 10:22 AM   #5
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K = bayonet mount
M42 (or M39, much less common) = screw mount

The former need no adapter, the latter do. As for the various "kinds" of K-mount, that's really just a function of what features the lens supports - they are all the same mount, physically. So no need to pay attention to the specifics of the mount - just look in the description of the lens itself to see if it supports autofocus or auto-aperture (allows camera to set aperture rather than requiring you to do it with the aperture ring).
03-08-2010, 11:15 AM   #6
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and then again

The above posts pretty much cover it, except:

* When used right, 3rd-party M42-PK adapters aren't bad. It's good to have an Official Pentax adapter. If you have several-to-many M42 lenses, and some K-mount lenses, and you do any amount of lens changing, it's good to have some 3rd-party adapters also, WITH THE SCREWS AND CLIPS REMOVED, to leave on those screwmount lenses. You'll see endless argument about this. I just don't have a problem.

* There's another kind of 3rd-party adapter with a flange on it. It's easy and safe to use, but it prevents the lens from focusing to infinity. It has its uses: on certain long lenses, on bellows, and on lenses used for portraits or close-ups where you don't *want* infinity focus.

* There are numerous types of screwmount lenses. The common M42 type (with a 42 x .75mm thread) will mount on zillions of old cameras, such as the classic Pentax Spotmatic. The common T-mount type (with a 42 x 1mm thread) takes simple adapters for use on Pentax, Nikon, Canon, Olympus etc bodies.

* 39mm threads are also common; those called M39 are usually Russian and use a simple adapter to fit into M42 cameras and adapters. Many enlarger lenses are M39 and can be used on bellows or macro tubes. But there is another type, not easily distinguished from M39, called L39 or LTM (Leica thread-mount). These CAN NOT be used on Pentax or similar cameras! (The glass-to-sensor distance is wrong.) Many Russian L39 lenses are on eBay; BEWARE!

* Other screwmounts: the earliest Asahi (Pentax) lenses were 37mm and I don't know if they're adaptable to K-mount, but you're not likely to encounter these. Some Miranda lenses are 44mm and I haven't seen any PK adapters. The Argus C3 'brick' has M34 threads, not usable elsewhere. Other odd sorts exist, but unless you like playing with glass fitted to bellows, they're not of much use.

* Some (not all) Nikon F-mount lenses can be force-fit onto Pentax K-mounts. The fit is snug but not tight; be careful not to dislodge the lens or it can fall off. That's no fun when you're in a canoe or something. Nikkors are nice glass -- I have an 85/2 that cost me US$3 and gives great results -- but they can only be used manually, same as all the screwmount lenses.

* Some Yashica and other lenses LOOK as though they should fit on a K-mount, but they don't. As mentioned above, some third-party lenses need slight surgery to fit. Always look CAREFULLY at an unknown lens, compare it to good lenses, before trying to stick it on your expensive camera. I keep an extra macro tube handy as a test bed.

I think that's about all I can add. Glass is fun. Enjoy.
03-08-2010, 11:31 AM   #7
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WOW

Thanks for your help everyone! It's hard to know what to look out for and what to avoid when your on ebay for lenses and a total newbie, but you guys are helping me out big time!

Now I know what all the numbers and letters mean, it's time to order some glass!
03-08-2010, 01:54 PM   #8
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QuoteOriginally posted by Just1MoreDave Quote
There are many M42 lens manufacturers and many variations on the mount, with a few designs that might need some assistance before they're usable... The main feature to look for on an M42 lens is a switch for the aperture, usually labeled AUTO/MAN or A/M. Otherwise you may have to modify the lens yourself.
You're right, I forgot to mention this. Look at the bottom of an M42 lens, the screwmount. Some have a little retractable pin, some don't. If no pin, the aperture is a PRESET -- you turn the aperture ring to the f-stop you want, and shoot. Some lenses have two aperture rings: one lets you set the f-stop, the other moves freely to let you quickly go from wide-open to the selected setting.

But small apertures and dim light make focusing difficult. So on a lens with a pin, and a screwmount camera that supports this feature, you can set the aperture to any f-stop, and compose and focus wide-open, with enough light to see what you're doing. Then you can push a stop-down button to preview the final picture; or just snap the shutter, and the camera automatically stops-down to your setting.

A lens with an M/A switch lets you choose either Manual (preset) or Auto (stop-down) operation. Put an adapter on such a lens, put it on your dSLR, set the switch to M(anual), and you're good to go. (First, go to Custom Menu and set Using Aperture Ring to PERMITTED.) If the switch is on A(uto), the lens will always stay wide open; your dSLR has no way to push that pin.

Now comes the tricky part: Some M42 lenses have a pin but no switch. They work automatically on the right screwmount film cameras, but not on other bodies -- like your dSLR. You need to hold the pin down. I superglued a few pins; now I can't get them unglued. (Solvent hasn't worked, and I haven't tried high-intensity UV yet.) Maybe I should have used a tiny bit of scotch tape. Anyway, be aware that if you're considering a M42 lens with a pin on the mount, an M/A switch is a Real Good Thing.

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