M42/K Mount adaptor on K-x?

Comments on a couple of non-Pentax brand M42 adapters.

My wife and I used to use Spotmatics a lot. When we decided to go properly digital we chose the Pentax K-x in the hope that we could use our old Takumar 42mm screw-in lenses for odd occasions.

I am well aware of the strong recommendations on this, and other forums, to buy only the genuine Asahi Pentax M42-to-PK adapter (the topic comes up frequently: try a search for adapter/adaptor + m42). However, being a tightfisted pensioner I hesitated about paying out over 60 pounds for a new genuine Pentax adapter, or even 25-30 pounds for second hand ones on eBay. We are only likely to want to use the old lenses very occasionally.

I have now bought, cheap on eBay, two branded "infinity-focus" (ie: flangless, flush-mounting) adapters. Here are some comments on them that others may find helpful.

KOOD "Made in Japan" PENTAX/M42 ADAPTER. These come up from time to time on UK eBay and I got one for under 5 pounds (plus postage) in very good condition, boxed, with the dismounting key. It is made from some light alloy and painted black. The paint seems well applied, but nevertheless there might be a risk of tiny flakes coming off and going into the camera. The locking spring, on the one I bought, looked distorted as though a previous owner had struggled to get it off the camera - this is the commonest complaint about non-AsahiPentax adapters. I would not even try risking it. I got a friendly local watchmaker to remove it - the spring is fixed to the adapter by the tiniest X-head screw I have ever seen, and it was in pretty tight.

With the locking spring removed, this adapter goes on and off the K-x easily, and when fully clockwise it is quite snug and I see little danger of the lens+adapter accidentally falling off.

The KOOD adapter has a small inward flange at the inner (mirror+sensor) end of the 42mm screw thread. The flange reduces the inner diameter at that point to 37.3 mm and it fouls the diaphragm actuating pin on the base of a Takumar lens, so one cannot quickly go from full aperture to a smaller aperture just by moving the Auto/Manual slider. One is effectively always on Manual from max aperture down to (or nearly down to) the smallest stop. On our Super Takumar 50mm lenses one has to click all the way down from f 1.4 to the desired stop. Only when going right down to f 16 does one have to engage "Manual", as the flange does not push the pin in all the way. Of course, while doing all this one risks disturbing the focus or framing slightly. If you could tolerate this, then the Kood, with locking spring removed, is a cheap adapter for occasional use.

Warning: one of our Spotmatic lenses is a late S.M.C. Takumar 28 mm. This lens has a tiny spring-loaded pin on the baseplate, just clear of the 42 mm screw thread. As far as I can see its sole purpose is to lock the AUTO/MANUAL slide lever when the lens is off-camera, to prevent accidentally changing the mode. The rectangular cutouts, for the dismounting key, on the forward face of the Kood adapter, clash with this tiny pin. One has to depress the pin (eg with a fine screwdriver or penknife blade) in order to fully tighten the adapter onto the lens. More importantly, it also fouls the cutouts when starting to unscrew the adapter from this lens, and one must be able to depress it before one can separate lens and adapter. If one is also using the adapter with the locking spring still in place, you are in a Catch 22 situation: you can't get the lens+adapter off the camera because you can't get at the locking spring to free it, and you can't get the lens off the camera+adapter because you can't get at the tiny pin to depress it clear of the adapter. Perhaps an engineer's thin feeler gauge would just do the trick if you could slip it in before the pin springs up into the cutout slot? I wouldn't risk it!

JESSOP BODY MOUNT ADAPTER. M42 Pentax-K. I bought one of these on UK eBay for just over 8 pounds (plus postage) in near-new condition. It seems better made than the KOOD adapter - chrome plated brass, I think. As the locking spring was in perfect condition I tried mounting it on our K-x body. It went on easily, but getting it off was a little stressful. It is said that the genuine Asahi Pentax M42 adapters do not need the demounting key to remove them: the spring can apparently be depressed with a fingernail. I found that I had to use a small screwdriver blade to fully depress the JESSOP locking spring, while easing it all back and forth with the demounting tool. Once bitten twice shy. I promptly removed the spring - it is held with a small slot-head screw.

Without the locking spring, the JESSOP adapter is a snug fit and I think there is little risk of a lens falling off accidentally. The tiny pin of the S.M.C. 28 mm (mentioned above) does not foul the dismounting slots in the way that it does with the KOOD. The adapter does not interfere with the diaphragm pin, so one can use a Takumar as a manual preset lens: chose the working aperture with the lever on "Manual". Focus at full aperture with the lever on "Auto" and then just move to "Manual" for the exposure.

With any of these flush-fitting adapters the Takumar 42 mm lenses have to be treated as dumb manual lenses. I would be happy to use the JESSOP brand adapter (sans-spring) with any of them, but I will keep the KOOD in reserve and probably never use it.

By contrast, we also have a good Tamron 90 mm macro lens, with some Adaptall mounts. I have recently bought a very simple Tamron Adaptall II "Pentax KM" mount, and the combination works well. Manual focus, of course, but the lens stops down from full aperture to whatever f-stop one selects during exposure and then snaps back to full aperture. No Auto/Manual lever on this, unfortunately, to check DoF. AE seems to work well on the Av setting. On Manual exposure mode I just check each histogram and adjust as necessary, when taking macro photos of stationary objects.