SMC Pentax 1,4/50 – newbie needs support

[avwasser]

Hello,
I am Carsten. And I have been reading this forum for quite a while with lots of profit. Unfortunately I am confronted with a problem now, for which I could not find a satisfying answer yet.
Recently I bought an old Pentax 1.4/50mm. It is the "K" version, the direct successor of the smc-super Takumar. My lens shows kind of a brownish opacity. First I thought of the "well known" yellowing problem, even if the K-version of the 1.4/50mm is not known as one of those Thorium lenses. Despite that, I tried different treatments with UV light, but they achieved no visible result.
I cleaned the outer lenses before the UV treats, to make sure, that the opacity has nothing to do with nicotine or similar dirt.
May be one of you has some tips or hints? In the end the opacity is probably only of cosmetical relevance (I am shooting with the lense and it produces pretty good results). But nevertheless the opacity disturbs me somehow.
Thanks in advance,
Carsten

PS: Please excuse my Germlish.

The first photo shows my Pentax lense in comparison with a (already sold) Revuenon. The second photo is a test shot.

[ManualFocus-G]

[avwasser]

Thanks Graham for your help with the photos. What did I do wrong? I could see them in the preview. But after submitting my post they were gone...

[fuzzywuzzy]

[IAZA]

I have smc m pentax 50/1,4, which has same yellowing. no problem to me.
Some people suggest to sun bathing the lens to make yellow go, but I never do that. like Graham said, I like it that way. bring it's own character

[themoleman342]

What UV treatments did you try?

It may just be that it didn't get enough UV for long enough. The most common method is placing the lens in a windowsill, front wrapped in tin foil and back elements facing the window. This bleaching method, however, takes months. Maybe you were just expecting faster results?

My procedure is a UVA bulb placed a couple of inches from the back glass and a front-surfaced mirror at the front. Even at 24-hour a day exposure it takes 2 weeks for 90% clear.

[martinsmith99]

I bought one with bad yellowing on (it was close to brown); a few days in the sun and UV blacklight cured the problem. There will always be a little yellowing as this is the colour of the coating.

[hoanpham]

shot raw, and shot at least one frame to calibrate the wb.
i have many lenses different makers, with different colors, no problem at all.

[s58y]

I used a 15-watt fluorescent UV bulb to clear a yellowed 50/1.4 S-M-C Takumar. Most of the yellow was gone in 2 days After 8 days, it was about as clear as a typical lens Of course, the yellowing in the S-M-C was probably due to radioactivity.

In your case, assuming the lens has no thorium, the yellowing may be caused by something else, and maybe the UV bleaching method doesn't work well?

[Keysersoze27]

Strange .....

I recently purchased a SMC Pentax 1.4/50 K exactly like yours (but higher s/n) and it's perfectly clear with no yellowing.

Two months ago as I was looking out for precise info about the K mount version of this lens I came into one of this lens with low s/n that had yellow glass..... could it be that some early K mounts had the same radioactive glass of the last rubber focussing SMC takumars ????

[avwasser]

Thank you all for your friendly answers!
@ Keysersoze27: I also thought, that the early 1.4/50mm K-versions might have Thorium lenses as the taks had. Therefore I tried to cure my copy by treating it with UV light. But, as I wrote, the cure didn't show a visible improvement.

@ themoleman342: I tried two different ways. In both cases the lense was exposed to the UV light for a week. First I had the lense sit under a blacklight bulb. After that I tried the flourescent tube of a device, that is normally used to detect counterfeit money (sorry for this kind of clumsy description, I couldn't find a propper term for what in german is called a "Geldtester").

PS: At last Mrs. Google was so kind to help me ... the term I was looking for is: Fraudulent Bank Note Detector

[RioRico]

I occasionally shoot film, usually B&W, but mostly I shoot digital in RAW. I have NEVER had a digicam with accurate AWB. Thus I tweak color cast|balance|temperature of almost every shot. To me, color casting by a lens is irrelevant. I make colors look the way I want them to look. That's integral to PP, part of the image-making process.

Is a truism: What you think you see, what you want to see, what the camera+lens sees, and what is 'really' there (if anything), are NOT THE SAME. If 'accurate' color rendition is needed, then calibrate and measure and make sure the setup is technically as perfect as possible. I don't need such, so I don't worry about it. Life goes on.

[fuzzywuzzy]

[Lloydy]

[avwasser]

Thanks, RioRico. You are right. But I came from the left I didn’t look at the lense with strict photographer’s eyes (that are already winking at Adobe’s Photoshop), more with the eyes of curiosity.

But, hm, you are probably also right in a kind of deeper meaning. Perhaps I should better put focus on the fact, that life goes on. Instead of curiously not getting anywhere. Otherwise I’ll later get into a hurry, that no image stabilization in the world will be able to fix.