Which Pentax screw mount lens?

[valen]

I have a Pentax S1A with a 55mm/1.8 lens that I recently had CLA'd.

The light

meter is unreliable, but I've gotten good results using a hand held

meter.

<p>I would like to add a lens or two - a wide angle (24mm) and a

telephoto of

some kind.</p>

<p>What pentax screw mount lenses are well regarded? Just to make it

more difficult,

I've heard that some of these lenses (such as the 50mm/1.4) are

radioactive

and while I'm not sure they present any health risk, I don't want a

radiocative

lens.</p>

<p>links about the radiocativity issue:</p>

<ol>

<ol>

<li> <a href=http://medfmt.8k.com/mf/radioactive.html>Info from

the Medium

Format Photography site</a> </li>

<li> <a href=http://www.photo.net/bboard/q-and-a-fetch-msg?

msg_id=0035DS>Requisite

photo.net thread on the subject</a> </li>

<li> <a

href=http://hps.org/publicinformation/ate/q1356.html>External Dose

calculations</a> </li>

<li> <a href=http://home.att.net/~jriegle/radioactive.htm>Geiger

Counter test</a></li>

</ol>

</ol>

[valen]

The photo.net link above doesn't work. Here's the info:

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0035DS

[jsbc]

there is a yahoo group called Club M42 that deals specifically with Pentax screw mount lenses (there is also a Spotmatic group that also discusses the camera bodies}. Fastest way is do a google search.

[hortensia_b.]

The problem with radioactive lenses is not so much that they pose a health risk as the lenses turn yellow. Pentax lenses that yellow include the SMC 50/1.4, SMC 35/2, and Super Tak 35/2 (version 2, the one with 49mm filter thread).

 

Pretty much all Pentax screw mount lenses are well regarded. The 24/3.5, 85/1.8, 105/2.8, 135/2.5 are all good. The 85/1.8 is especially pricey. A good non-Pentax screw mount wide angle lens is Mamiya's SX 21/4.

[michael_armstrong1]

There is a cure for the yellowed lenses. Not my idea, but I learned of it from the folks at the spotmatic group site. There are many contributors, but Ray Allen and Gene Poon devote a considerable amount of time helping people, including this remedy.

You can read the complete story at that site, but basically you put the lens in the sun, rear element toward sun, and let the UV do it's job. It takes time and there are many variables such as summer/winter etc. but it eventually whitenes the once brown lens.

Best regards.

Mike