geeky,  hobbies,  photography

Manual Lenses, EOS Bodies

Pentax K to EOS EF adapter
Pentax K to EOS EF adapter

Christmas arrived a little late this year, nurse but today, find I finally got the Pentax K manual lens adapter for Canon EOS cameras I’ve wanted for some time. A less paranoid friend of mine, pharm Kent, ordered one from some random guy in Hong Kong via eBay and PayPal for me. Fortunately, he had no problems with the transaction, as it arrived about 8 days after clicking on “buy it now” and paying. The only sketchy thing about the whole process is that the seller marked on the customs form “gift”. However, that’s up to him, as it’s up to the person shipping an item to sign off on it.

K to EOS EF adapter on Pentax lens
K to EOS EF adapter on Pentax lens

Over on the above left is how it looks. The metal looks well-machined; not flimsy at all. The K-mount lens mounts securely to the adapter, and the adapter snaps into place on the camera just as securely as a Canon-branded lens would. Impressive. If anything, the fit of the adapter to the lens is a little too tight, as it’s a little difficult to remove from the lens when you’re done with it. This seems preferable to a loosey-goosey design that feels untrustworthy, though, so I’m not complaining. The autofocus confirmation chip is just expoxied on there, but it feels very secure.

Pentax SMC 50mm f/1.4 on a Canon Rebel XTi
Pentax SMC 50mm f/1.4 on a Canon Rebel XTi

That’s all nice; how’s it work? I’ll cut to the chase: very well! Beyond being a nice, precision chunk of machined metal, infinity focus is perfect and Canon’s camera firmware makes it surprisingly un-painful to use the lens with it. It’s easier to use than I thought it would be, which is a pleasant surprise. Basically, you set the camera on “Av” aperture priority mode, focus and shoot.

That’s an oversimiplification of the process, as there’s a few gotchas. First of all, the Canon EOS system does all lens functions electronically: focusing; identifying the lens; setting the aperture for a picture, etc. Manual focus lenses can’t do any of this, so not only do you have to focus yourself, but you have to play with the aperture control to take pictures. SLR cameras allow you to compose with the lens “wide open” (at the maximum aperture) so what you see in the viewfinder is bright, and easier to focus. With this adapter, you have to open the aperture yourself to compose; then close it down to whatever you like, before you take your picture.

Infinity Focus works fine
Infinity Focus works fine

This is where Canon makes it easy: the camera is always figuring out the correct exposure for a scene, regardless of what aperture you’ve manually set. This is called “stop-down metering”. Once you’ve got your composition, focus and aperture chosen, you just press the shutter button.

The other gotcha is that even though it has a focus confirmation chip on it, Canon cameras won’t focus with an f-stop slower than f/5.6. (I don’t think any brand of camera does, for that matter.) So, it really is best to focus and compose with the lens aperture set wide open, and then set the aperture down at the last moment when you’re ready to take your picture. This is all stuff that happens automatically with SLR cameras made since the 1960s (well, except for autofocus).

A few final notes about all of this.

If I owned Nikon cameras, I wouldn’t need an adapter to use old manual Nikon lenses; and the whole process would be easier. In theory, all Nikon lenses made since 1977 should work on newer Nikon cameras; and lenses made between 1959 and 1977 can be converted to “AI” (auto-indexing) to have that same compatibility. In reality, the list of caveats and exceptions is about a mile long, and varies from camera body to camera body. The cheapest Nikon DSLRs, the D40, D40x and D60, are also the worst offenders when it comes to incompatibility, so your mileage with that will vary greatly.

I can’t imagine being a pro and putting up with any of this. Certainly, a pro will just buy the latest Canon glass and forget all about this adapter stuff. The glass is all an investment and a write-off, so there is absolutely no point to any of this playing around. Good thing I’m not a pro; this is just fun! 🙂

And now, for the whole point of the exercise: Using nice, (relatively) inexpensive old Pentax glass with my DSLR. So far, I’m very pleased with the results. See for yourself:

Horse Head
Horse Head, at f/4; Pentax SMC-M 50mm f/1.4 lens

Nice and sharp, isn’t it? I like the quality of the background blur, too.

Scary Thornbush, at f/2; Pentax SMC-M 50mm f/1.4 lens
Scary Thornbush, at f/2; Pentax SMC-M 50mm f/1.4 lens

Oh yeah. This is verrry nice!

And now, for a few shots showing the same scene with different apertures. (The lighting was kinda weird, a combination of cloudy light through the window and incandescent overhead, so don’t read too much into how the colors turned out… that isn’t the point to this group of pictures.)

Trellis Photo at f/1.4; Pentax SMC-M 50mm f/1.4 lens
Kalanchoe Trellis at f/1.4; Pentax SMC-M 50mm f/1.4 lens

Trellis Photo at f/2.8; Pentax SMC-M 50mm f/1.4 lens
Kalanchoe Trellis at f/2.8; Pentax SMC-M 50mm f/1.4 lens

Trellis Photo at f/4; Pentax SMC-M 50mm f/1.4 lens
Kalanchoe Trellis at f/4; Pentax SMC-M 50mm f/1.4 lens

Trellis Photo at f/5.6; Pentax SMC-M 50mm f/1.4 lens
Kalanchoe Trellis at f/5.6; Pentax SMC-M 50mm f/1.4 lens


  • Ed Ablola

    Glad to hear you’ve got the adapter. Been researching since last year about this. Was ecstatic to find it on your blog. Hope I could get one for myself as I’ve got a few old pentax lenses from my dad.

    Kudos to you, this is the next best thing to buying a pentax dslr body.

  • boombadeus

    Ed, I knew about the possibility for a while before I finally got one. I still don’t like the primary way of getting one (eBay, direct from China, etc) but it seems worth it.

    Given that this isn’t even a Pentax SMC-A lens (where the camera can set the aperture itself), there’s probably not much more an actual Pentax DSLR body could do than the Canon, other than perhaps record the f-stop that was actually used for the photo. (You’d still be using Av or Manual mode.)

    Tony, the old ones feel so nice. Newer ones just feel so plasticy…

  • Nick


    I’m thrilled to have found this posting. I’ve been interested in this for a while now. My father-in-law has some great old Pentax lenses from his 6X7. I wanted to try to use them on my Canon 40D. I found an ebay seller that goes under the name – goshotcamera. Is this the seller that your friend used? If not would you be able to find out who they bought it from? Thanks for the help!


  • Nettie

    Hiya I was searching for someone who is doing the same sort of thing as me.. I have received my new Eos to K mount today and I placed it on a lens now I cant remove it off the lens…

    I play around with a few different adaptors on my canon such as the M42 adaptor for the pentax screw mount and get great results with a helios lens on that as well as some SMC takumar lenses..

    No I though I would try and adapt some pentax Bayonet mount lenses and I have been foiled in removing the adaptor to use on a different lens…

  • boombadeus

    This adapter is pretty difficult to remove from the K-Mount lens. I don’t know if yours is the same brand as mine, but on mine, there is a little spring catch you have to hold open in order to remove the adapter from the lens. Not only that, but it’s a very snug fit… feels like you might damage the lens as you twist it off.

    Anyway, it definitely should come off. Just be careful!

  • Ana

    Nice post! I just purchased my first two Pentax lenses for my Rebel XTi along with an adapter ring that should be arriving soon, so your previous experience is highly useful.

    Thanks for sharing

  • boombadeus

    Peter and Ana, I’m glad it was helpful! Hope it’s working out for you. The Pentax SMC M 50mm f/1.4 lens rarely comes off my DSLR now, so I guess you could say it’s a hit with me!

  • petreksw

    dear boobbadeus
    thanks for sharing

    may i ask
    can the smc 50mm f/1.4 lens autofocus on a eos 40D or does it need manual focus? i am looking to get one myself but is worried about whether its a hassle to shoot with

    hope you can enlighten me 🙂

  • boombadeus

    Oh, it’s all manual. No autofocus, no auto aperture, nothing! There are no electric contacts on the SMC-m 50 f/1.4 lenses, and that’s what the Canon EF mount uses to control lenses. It’s worth doing it, anyway…

  • Tanya

    Do you have to remove the lever on your lens? I have a smc-a 50 1.2 and a cimko mt series 80-200mm lens and have been wanting to try this adapter forever but am so can you email me with some details please. I have some questions. thanks