Yellow tinted Super Takumar elements

Discussion in 'Pentax' started by rogerdaltx, Nov 20, 2008.

  1. Hi guys I've got a 50mm f/1.4 Super Takumar M42 that I picked up as part of a garage sale score last week with a bunch of other gear. This is the one with the radio active elements that can something get a yellow tint. It's been stored for YEARS and YEARS in someone's closet and is mint (other than the element yellowing :-( The standard answer for clearing the tint up is to put the lens in the sunlight and leave it. Which is supposed to reduce / remove the yellow tint. It's been on my kitchen window seal with a piece of shiny tin foil under the back element and the front element pointed toward the light for about a week now and I can't see a change in the yellow tint. Has this actually worked for anyone on here? Any idea how long it's supposed to take? Thanks /Roger
     
  2. Stupid question but does a white wall (say) look yellow when you look at it through the lens?
     
  3. rnt

    rnt

    If it's the UV in sunlight that fades the color cast then the window glass is probably filtering out a lot of it. Short of putting it outside or in a tanning booth I don't know what to suggest...
     
  4. Roger, I read about it originally on the classic camera forum here : http://www.photo.net/classic-cameras-forum/00E6Pq and then there was this: http://www.photo.net/classic-cameras-forum/00ATf1 both of these discuss the process of clearing the yellow ... from the same sup tak lens.
     
  5. Thank for the links Rose and Orlando thank you very much for the link to your detailed experience. It seems the clearing process can take weeks or longer and that it is the UV rays that "bleach" out the color. I may go the track of others and find a UV florescent bulb and setup a box so the lens catches most of the light. Seems more efficient than sunlight in a window (and less dusty). A common thing I read is some people confuse a "gold" coating with the yellow discoloring. I don't think that's what I'm dealing with as the yellow seems to be on an inside element and deepens in color more to the center. Here are a few shots of the lens.
    00RYeC-90501584.jpg
     
  6. Second shot trying to catch the surface of the lens. White balance is custom on the notebook paper behind the lens.
    00RYeF-90501684.jpg
     
  7. And for comparison here is a shot of an SMC Super Takumar 50mm f/1.4 that I bought a couple of years ago.
    00RYeI-90503584.jpg
     
  8. Placing a lens on foil in direct sunlight seems like a lot of light/heat buildup... Would I be correct if suggest that you might be risking warped shutter blades, or problems with oil causing the shutter blades to become sticky???
     
  9. hey roger i own two of these lenses and i performed the treatment mentioned to both,i found that an average of two weeks was more than enough to make them clear with no side effects other than the joy of a great lens! good luck!
     
  10. the UV bug zapper (incandescent) produces tons of heat. Besides it has very low UV output. the UV fluorescent is good though, mine came with an electronic ballast, very little heat buildup. Yes the Super-Tak (not SMC Tak) has a gold coating, but the photo above clearly shows the yellowing of the lens element.
     
  11. Hi: I recently cleared an S-M-C T50/1.4 of the yellow tint issue - but I pointed the REAR element at the UV source.
    Leaving the lens cap on the front, I wrapped the entire lens in foil (to reduce heat gathering by the black paint) save the rear element. I placed the lens on the rear cap in a south-facing window, angled upward to about the angle of the sun for that season.
    Fully clearing the tint took three weeks.
     
  12. Good luck Roger, you clearly have a yellowed element. Following one procedure or another you'll soon be on your way to taking some great radioactive photos :)
     
  13. Thank for the input guys. I ordered a compact fluorescent twist black light off of Amazon which will be here in a couple of days. Will set the lens up with it probably in a foil lines box and see what happens after a week or two. Will post a few follow-up photos of the results. The bulb is a Feit Electric BPESL15T/BLB 13-Watt Bulb Compact Fluorescent Twist Black Light http://www.amazon.com/gp/product/B000I1AE20
    00Ra4o-91301584.jpg
     
  14. Wow, this actually works. A week in a window seal didn't do much to correct the yellowing issue on my Super Tak. But what a difference after just 24 hours under the black light. Below is a shot of the same lens same lighting conditions and same white balance. It's a significant improvement in a short time. Think I'm going to leave it a few more days to see if it get's any better.
    00RcZu-92541784.jpg
     
  15. The effectiveness of the window sill treatment might depend on how old your windows are. Newer windows (made in the last 10-15 years) tend to filter out some of the UV rays. Older windows probably don't filter the UV nearly as much.
     
  16. I recently purchased a Pentax Spotmatic II and a 50mm f1.4 Super Takumar lens for wedding photography here is Los Angeles. The lens was purchased off Ebay for $60. It was in great condition but had bad yellowing as well. I wrapped it in tin foil and left it on the windowsill for about 3 days, checked on it and nothing changed. The window just filters out too much UV. So I went to Home Depot and bought this plug in GE Black light. It is 22"" T8 form fixture. I put the lens in a cardboard box lined with reflective aluminum foil. Placed the foil wrapped lens with the rear element facing the tube (the tube was about 4-5" away. After just 24hrs, the lens looks crystal clear. the viewfinder image now looks much brighter, and I see no color cast between what my eye sees and what I see through the lens. Blacklights are the way to go with these things.
    -Steve Steinhardt
    Blog
     

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