Thoughts on M42 lenses for K20D

[dugger]

Hey group, anyone have experience with M42 lenses on a K20D? Caveats? Probs? Advantages? Anybody's adapter

ring better than the others? Thanks.

[andrewg_ny]

Everything I read says go for the genuine Pentax adapter, without the additional flange. The other adapters often sacrifice infinity focus. In some ways the M42 might be better than early K-mounts as you can make better use of Av mode.

[le-plume]

Yeah, M42 adapters are a bit tricky to remove in any case; I wouldn't want a cheap one to get stuck on one of my K-mount bodies... I'd go for the original Pentax product, even though it's a bit more expensive.

 

Andrew: what you mean by "better use of Av mode" is that your lens will be stopped down without using the green button, right? Just trying to make sure I understand the use of non-A lenses on KxxD bodies before I finally buy one...

[paul_noble]

I have used the Super Takumar 50mm, f/1.4 lens from my Spotmatic on my K10D, with good results. I have a

flangeless third-party adapter with the locking spring removed. It works just fine. I leave the adapter on the lens,

effectively converting it into a K-mount lens. With the locking spring removed, it goes on and off the camera normally.

Even though there is no locking pin, as on a true k-mount lens, friction is enough to keep the lens securely in place.

 

I simply put the lens in M mode, the camera in Av mode and go. Since I grew up with an original Spotmatic, stop-

down metering doesn't bother me at all. I just set the aperture on the lens and the camera picks a shutter speed.

 

That extra two and a half stops (over the kit lens) is great for low light. And the S-T is a very sharp lens.

 

Paul Noble

[miserere_mei]

Like Paul said, Av all the way. It's actually more convenient to shoot with M42 than with K or M series lenses. What can be a little inconvenient is mounting the M42 lens to the camera. Some people attach an adapter to the lens and then drill a small hole on the back of the lens for the locking pin. I have a 200mm f/3.5 like this.

 

The other advantage of M42 lenses is that you get instant DoF preview.

 

Damn, I need to go on eBay and buy myself a Tak now...

[shots worth sharing]

See Hin's thoughts on the subject here:

http://techtheman.blogspot.com/2008/05/genuine-pentax-m42-to-k-adapter.html

[mountainvisions]

I actually attached my adapters semi permanently with locktite. Now reading all the post, I realize I do exactly

what Paul is explaining.

 

I just got the Adorama adapters, took off the spring/locking piece, and now my lenses don't quite click on but

they also won't fall off. I have thought of adding a pin but been to lazy and this hasn't failed me yet.

 

I think the M42s are better built than even the current limiteds, they are a pleasure to manual focus, they have

real DOF markings, they are smooth, they are also heavy and seemingly overbuilt by todays standards.

[miserere_mei]

Justin wrote: "M42s rock."

[mountainvisions]

Nailed it!!!

[celasun]

All my M42 lenses need various amounts of exposure compensation on my K10D and the amount varies with the

chosen aperture. Others reported this behaviour previously and provided more detail; I suggest you check them... <p>

Generally speaking, for apertures like f/1.4 and f/1.8 you may need up to +2 exposure compensation while at f/11

+0.5 may suffice...

[hinman]

These are links I send Rose when she asked me about the custom manual setting in using M42 lens:

 

#1 Custom Setup for M42 lens

 

http://techtheman.blogspot.com/2007/09/setup-with-pentax-m42-mount-lens.html

 

Other links are not as important but here as a reference when you need

them:

 

#2 Pentax Genuine M42 Adapter

 

http://techtheman.blogspot.com/2008/05/genuine-pentax-m42-to-k-adapter.html

 

#3 Warning on 3rd party M42 adapter

 

http://techtheman.blogspot.com/2007/12/warning-on-bower-m42-adapter.html

 

#4 Pentax M42 Adapter

 

http://techtheman.blogspot.com/2007/09/pentax-m42-adapters.html

 

#5 How to convert M42 to K mount lens

 

http://techtheman.blogspot.com/2008/02/how-to-convert-m42-to-k-mount.html

 

#6 Search All of Hin's M42 articles

 

http://techtheman.blogspot.com/search?q=m42

 

Also I have a blog post on Pentax Lens Research Bookmark in my blog:

 

http://techtheman.blogspot.com/2008/08/pentax-lens-research-bookmarks.html

[dugger]

I asked for a "brick" and you all gave me a "wall". Thanks for the info! Hin... you da man!

[paul_noble]

One thing that no one seems to have mentioned, Doug; some third party adapters will not allow infinity focus. Here is an example of one:

 

http://cgi.ebay.com/SCREW-MOUNT-LENS-TO-PENTAX-K10D-K100D-K110D-ADAPTER_W0QQitemZ280265539023QQcmdZViewItem?hash=item280265539023&_trkparms=72%3A1205%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

 

Note that it has a large flange that will sit outside of the k-mount opening. This creates extra thickness between the lens and the sensor, preventing infinity focus. That's fine if you only intend to do macro work, or portraits, but not for general use.

 

Compare this to the genuine Pentax adapter as shown in Hin's links. Both the genuine Pentax adapter and the better third-party adapters fit flush within the k-mount opening and do not add any thickness to the camera.

 

I have never used a genuine Pentax adapter. Mine is a third party one, but it works well. The genuine one may be a little more precisely machined. I must admit that, when I first got it, I had a little trouble getting it off. It took a little time to get the hang of it and I had to use the tool that came with the adapter. I'm told that no tool is needed for the genuine article. Once I removed the locking spring, I had no further trouble. Now, I just twist the lens off, the way I would with a true k-mount lens. Sometimes the adapter begins to unscrew from the lens, but that has not been a problem.

 

Paul Noble

[andrewg_ny]

I don't own any M42 so haven't experienced this first-hand. Why would M42 have particular metering problems? They meter with the aperture already stopped down--there's no autoexposure program logic involved, the lens doesn't TELL the body what aperture it is set to, it JUST IS that aperture. Why wouldn't this be especially "accurate"? Does everybody's experience match what Bulent C. describes?

 

The thing that comes to mind is that the body will fall back to center-weighted rather than 16-segment matrix metering--and this will likely result in an increase in amount of exposure compensation required as it won't compensate for backlighting or frontlighting as much.

[mountainvisions]

"Sometimes the adapter begins to unscrew from the lens, but that has not been a problem."

 

A little loctite will solve this. Don't get the super strong stuff but either way it will come off when you want it too, just not before (most likely).

[dugger]

Paul, yes I'd like to make sure that infinity would be available... thanks for the tip. Although, it looks like a genuine Pentax adapter is not very accessable in the U.S. Going down to my local camera store tomorrow and see if one can be ordered.

[miserere_mei]

Doug, you can get the genuine ones off eBay, although they are $40 or so.

 

On my Jupiter-9 I use the flanged adapter (which is permanently screwed on) as it has a little bite on the edge

for the locking pin. Because I only use this lens for portraits, it's not a problem that I don't get infinity

focus, and in fact, I get close-focus capabilities, which is even better :-)

 

The flangless (flush with the body) adapter is fine, except not all the lenses I've used will remain held by

friction (hence my preference for the flanged one). It's not an authentic Pentax adapter, so that might make a

difference. As for the tool required to take it off, I just use the flat screwdriver on my pocketknife; I'm sure

a pen would work fine too, as all you need is to press down the little spring tab.

[zane1664879013]

Doug, the Pentax-brand adapter is available from their online store:

 

http://www.pentaxwebstore.com/detail/PTX+30120

[christer_medin1]

The Pentax adapter I can release from the camera just by pulling the spring with a finger nail.

 

Have used the following M42 on my K20D:

Super Takumar 50/1.4

SMC Takumar 50/1.4

Vivitar 135/3.5 (with T mount)

Tele-Lantar 135/2.8

Tele-Astranar 400/6.3 (with T mount)

Super Takumar 28/3.5

Industar 50/3.5

 

Out of these, the Tele-Lantar and Industar are a little 'wobbly'. They don't have a wide flange on the rear like the rest so they only touch the adapter; the other lenses butt up against the camera's lens flange and mount solidly.

[jansky]

Hi there!

Has anyone had problems using a lens such as the Fujinon 50mm f/1.4-16.0 or similar ones that have the pin for closing the diaphragm that should somehow be pushed in when the lens is on the camera? I'm asking because I cannot see (I don't have the camera yet) how the Pentax adapter will push it. Or the K20D is made so that it will keep it pressed?

[celasun]

Jan Lai,<br>

I have that same lens. You can use it at its widest aperture setting only as there is nothing in the digital bodies to push it.<br> However, a skilled technician can push and fix (glue) that pin permanently for you. Then, you can use it just like any other manual M42 lens. Good luck.

[jansky]

Hi Bulent,

actually I've found a better solution: I had used the same when I had a Canon 350D and wanted to use my M42 lens

with it. I have used a motorcicle piston ring glued inside the adapter (you can see a picture in this <a

href="http://www.photo4u.org/viewtopic.php?t=121105">italian

forum I've written a post in</a>) and this gives me the chance not to

ruin the lens that can still be used with it's original camera without blocking the little pin with glue.

Thanks anyway.