Anyone got experience of PK mount lenses on EOS bodies?

[guybrush]

Hey,

I stumbled across a bunch of old Pentax K-Mount lenses earlier, I'm currently deciding whether to sell them on or if I should have a little play with them.

I've been reading up information on how to attatch them to an EOS body, however I'd prefer to get some proper feedback from someone who has actually tried this before I go jamming lenses into my camera and messing it up.

I'm using a 500D, I've seen that these lenses don't work with full frame EOS bodies. I'm not entirely sure why that is, something about the aperature trigger at the back of the lens protruding into the body?

I read a scary page about how some lenses clash against the mirror when you're trying to focus into infinity - what does this mean and how come it happens?

Also, is it really necessary to get an AF confirm chipped adapter? What are the benefits of this over a standard adapter.

I've also read problems about having to set to max aperature and then stepping down before you take your picture. I take it this is because the camera can't compensate for the lack of light when using a slow aperture, therefore making it impossible to see anything through the viewfinder? I possibly have that one completely wrong.. feel free to correct me!

The lenses I will be trying out are..

Hanimex 75-300mm f/5.6 Macro
Pentax 50mm f/1.7
Carl Zeiss Jena 135mm f/2.8

Thanks for any help.

 

[trencheel303]

If that haminex is anything like the one I have (80-200 I think) the quality will be horrible even on crop. It was like a toy lens!

 

[Musicman]

I'm using a 500D, I've seen that these lenses don't work with full frame EOS bodies. I'm not entirely sure why that is, something about the aperature trigger at the back of the lens protruding into the body?

I read a scary page about how some lenses clash against the mirror when you're trying to focus into infinity

You've answered your first point yourself. This is the reason many lenses won't work on full frame bodies - mirror strike.

On a 5D one of the ways round this is to shave the mirror (literally grind a small amount off the bottom edge) so that it doesn't hit the protruding rear element of some non EF lenses when it swings out of the way to allow light to fall on the sensor.

Generally, mirror strike is less of an issue on crop bodies like the 500D as the mirror is smaller than one you'd find on a full frame body, but the registration distance is still the same, so it's less likely to clash with a lens.

I can't speak about the specifics of K-mount lenses, though.

 

[guybrush]

If that haminex is anything like the one I have (80-200 I think) the quality will be horrible even on crop. It was like a toy lens!

Hey,

It's the same lens as this one here http://www.flickr.com/photos/colinsd40/4392739057/ Except his is obviously an M24 mount whereas the one I have is PK. I can't find any photos on his stream that he's taken it with it though.

You've answered your first point yourself. This is the reason many lenses won't work on full frame bodies - mirror strike.

On a 5D one of the ways round this is to shave the mirror (literally grind a small amount off the bottom edge) so that it doesn't hit the protruding rear element of some non EF lenses when it swings out of the way to allow light to fall on the sensor.

Generally, mirror strike is less of an issue on crop bodies like the 500D as the mirror is smaller than one you'd find on a full frame body, but the registration distance is still the same, so it's less likely to clash with a lens.

I can't speak about the specifics of K-mount lenses, though.

I read about having to shave the mirror, it sounds like a completely ludicrous thing to do! I'd never harm my poor little DSLR like that.

Anyway..

I did something possibly a little stupid.. Since I was so eager to test out these lenses, I just placed them infront of the my camera and snapped away! The lighting at the moment in here is rubbish, and since the 75-300mm is only f/5.6 I simply cannot test it adequately enough.

However, I atleast now know that they will work - at least they won't shatter my SLR.

It's a shame I only have the 75-300mm and 50mm lens, as I really don't need a 50mm lens, so if I buy an adapter I will purely just be buying it for the 75-300mm, and if that turns out to be poor like Trencheel suggested then it'll be a bit of a waste of money! Especially since I don't reckon I can get away with a cheapo from eBay as it is an incredibly heavy lens, and I've read that people have had issues with the lenses falling off the adapter if they're too heavy.

If it works however, it should do me nicely until I get a 70-200L.

If anyone is interested I'll upload a few tests shots I did, however they are incredibly poor and I can't focus the damned things proplery whilst I'm trying to hold it against the camera!

Oh yeah, also - I found out the Carl Zeiss Jena 135mm is actually a Praktica B mount, and supposedly has issues with infinity focussing? I really don't have a clue why that is and the Pentax K mount lenses do. If anyone knows the answer to this then I'd love to know! I don't think I'll invest in a PB mount if that really is the case.

 

[photon]

People modify the tastier PKA and PK lenses for their Canons, but it's a one-way process.

Another option for you would be to get an M42 adapter and concentrate on old M42 lenses. The Tamron Adaptall-2 range has some excellent performers and could also be used economically on the better Nikon bodies. The PKA mount for them is now very expensive but the Tamrons are still bought by Pentax users, so you shouldn't lose anything if you decide to sell.

 

[Musicman]

Oh yeah, also - I found out the Carl Zeiss Jena 135mm is actually a Praktica B mount, and supposedly has issues with infinity focussing? I really don't have a clue why that is and the Pentax K mount lenses do. If anyone knows the answer to this then I'd love to know! I don't think I'll invest in a PB mount if that really is the case.

The registration distance on Praktica B mount is 44.4mm. That for Canon EF is 40mm. This leaves 0.4mm in which to fit an adapter, which is mighty thin.

So, with a slightly thicker adapter, your 'B' lens sits a little further forward from the plane of the imaging sensor than it should - consequently you can't quite reach infinity focus.

I found an ebay listing for a PB to EOS adapter, which comes with this note

**-this adapter will focus to infinity with most lenses, but it has some problems with wide-angle lenses with low aperture. After stop down to f/4 everything is ok. The same problems with 50mm f/1.4 lens (It has to be stoped down a little to focus to infinity, but You can still use it for portraits with aperture f/1.4 or f/1.8).

What it's doing there presumably is allowing the wiggle room you have with DoF at smaller apertures to take up the slack to reach infinity.

P.S. Have you read Bob Atkins page on Using Manual Focus Lenses on Canon EOS bodies? It has some useful information. I've had it in my bookmarks for ages.

Pentax K's registration distance is 45.5mm. 1.5mm is plenty enough room to get a decent bed of metal for a lens, issues with the aperture levers aside.

 

[guybrush]

Thanks for that link, it was very useful - and oddly enough, it also helped me understand how tube extenders work for macro functions!

I've gone ahead and ordered a PK adapter, I won't bother with the PB one as it's extra cost and I don't think I'll get much use out of it.

For what it's worth, finding a 75-300mm macro lens in my garage, and being able to use it on my canon for the price of a £15 adapter is pretty good I reckon, even if it does only match the optical quality of the EF-S 55-250mm and other low end consumer telephoto zooms. It may lack autofocus and everything else, but it sure as hell looks and feels fancier!