clixpix Loc: Surprise, Arizona

Hi:

I have some older Pentax lenses that I would like to try using on my Canon 50D for fun. I bought the Fotodiox PK-EOS adapter. The adapter fits the lens and camera body ok except that I am concerned that the tab sticking out of the lens will hit the mirror when the shutter is pressed. i do not want to try it until I get more information. Maybe i ordered the wrong adapter. Anyone have experience with this combination or have other suggestions. Thanks in advance for the help.

Joe

See the metal tab on the lens?

(Download)

amfoto1 Loc: San Jose, Calif. USA

I don't have specific experience with that combination...

However, I suspect you'll be fine using the lens with the adapter on an APS-C model such as the 50D, which has a smaller mirror to match the sensor size, and thus more clearance for that tab.

You can probably check it yourself. Put the adapter on the lens and measure how much the tab protrudes. Then remove any lens that's on your 50D and put it in Mirror Lockup, Live View or Sensor Cleaning mode, any of which will flip the mirror up... then measure the amount of clearance between the bayonet mount outer surface on the camera and the edge of the mirror. That should tell you if it's okay, since the edge of the mirror moves in sort of an arc so that the least clearance is when it's flipped fully up out of the way (you also could probably just measure from the edge of the light seal foam that surrounds the focus screen, which should pretty closely match the size of the mirror itself, without actually causing the mirror to flip up).

It might be more of a problem.... possibly requiring modification of the vintage lens to remove that tab... if you were using it on a full frame camera instead. But I suspect you'll be okay on an APS-C model.

blackest Loc: Ireland

On the 1D mark II it hits the mirror 1.3x Crop Aps-c Canon maybe ok there probably is more clearance, a full frame definitely not.

One way round it is to use a 1.4 teleconverter and remove or bend that arm out of place on that. You will want to use manual aperture anyway. Even some m42 lenses can have problems at some focusing distances if the rear element moves to far into the mouth of the mount.


http://photonotes.org/articles/eos-manual-lenses/

Sadly it also appears that it isn’t possible to make adapter rings that let you mount Pentax K (bayonet mount) lenses on EOS cameras with EF lens mounts. The Pentax K diaphragm coupling lever physically interferes with such a possibility. So you’d have to modify the lens (or the camera) to make such a conversion possible. Note that this does not apply to cameras compatible with the EF-S mount. The design of the EF-S mount, with its smaller mirror box thanks to the 1.6x crop factor, coincidentally permits the use of such lens adapters.

SharpShooter Loc: NorCal

Joe, why don't you ask Photodiox?! ;-)
SS

imagemeister Loc: mid east Florida

This is a long known problem with Pentax K to EOS conversions. Most people shorten the aperture lever.

rehess Loc: South Bend, Indiana, USA

There aren't a whole lot of options here:

(1) That lever has always been an integral part of K-mount. It is a part of every K-mount lens I have, dating back to the Pentax-M lens that was kitted with my first SLR, which I purchased in 1979; in fact, every Pentax (and the only Ricoh) K-mount lens I own has a wider (and almost as long) shield next to the lever.

(2) The thickness of the adapter is dictated by the difference between the K-mount flange distance and the EF-mount flange distance; they could make the adapter thicker only by including a glass element, which would diminish the quality of images taken with the system while simultaneously adding to the cost of the device.

Unless these lenses are really special to you, I would think twice before amputating the lever, since the lenses would no longer be of any use on a genuine K-mount camera.