Super Takumar Lens

Discussion in 'Medium Format' started by dave_cheng|1, Jun 8, 2004.

  1. I have a Pentax 35mm SLR model SL vintage camera that was a very
    special gift to me from my family when I was a teenager. I care
    very much about it although I don't use it any more.

    My question is kind of related to P67. I found that my 50mm/1.7 of
    this camera is
    suffering from the well known yellowing illness. Well, that's OK for
    me as I don't really use it any more. However, I realized that it is
    a Super Takumar. I understand that there are many old P67 lenses out
    there that are also Super Takumar lenses.

    Does any of these old P67 Super Takumar lenses suffer from the same
    yellowing symptom? Will they eventually do? Should I avoid old
    Super Takumar all together? Is there a cure? Does the yellowing
    impact image quality in terms of colors at all?

    The yellow cast of the lens is really a reflection of light from the
    front glass. I suspect there will be any real impact to image quality.
    What do you guys think? Thanks.

    Dave
     
  2. Dave - I had a P67 105 mm lens with this problem. It was useless for color photography giving everything a yellow cast. I read subsequently that if you expose such a lens to strong sunlight for a while the color fades. I have not tried this though.
     
  3. stemked

    stemked Moderator

    My understanding is that this is an issue with a certain type of radioactive glass used in some Super Takumars that made the lenses go yellow. It isn't in any of my old SMC Super Takumars, which are younger than the straight Super Takumars. Neither of my Takumar 67 lenses (135 or 200) have this problem, but it is interesting to note the previuous poster has this problem. It would be interesting to find out if there was an era of 67 glass that has the same type of glass.
     
  4. I wouldn't avoid all Super Takumars in general. I have only heard of problems with the 105. I own the 150 Super Takumar and it is a fine lens. Be aware that the Super Takumars were not 7 layer coated but were probably a 3 layer coat. The SMC started with the SMC Takumar. There were not a lot of different focal lengths made in Super Takumar. You will never see a 45mm Super Takumar nor a 165LS Super Takumar, as examples. Concerning radioactive glass; designers wanted to find a glass with an extremely high refractive index and so turned to metals that were very dense. The higher the glass density the higher the index in general. Many radioactive elements are very dense. High index was important in correcting spherical aberration.
     
  5. I had a Super Takumar 105mm f2.4 that had yellowing glass. It's the only P6x7 lens I've ever seen this problem on.
     
  6. yellowing glass is in fact from "radioactive" lens elements and their decay. This is not dangerous unless it is constantly kept close to your eyes. MANY lenses from the 60's to 70's used these lenses ( many with thorium elements ), including Leica, Canon and Pentax to name a few. To get rid of the yellow, follow this procedure:
    "you can "clear" yellowed radioactive glass in some early high performance lenses by sitting them in direct sunlight for about a week. wrap the lens in aluminum foil to minimize heating, leaving the glass exposed, and set it on a windowsill in the sun. Word has it that if the problem was radioactive yellowing, it will be clear as new in a week. PN member(s)"
    This works but pay attention as to not cook your lens
    www.antiquecameras.net
     
  7. Very interesting. I will give it a try. But why wrap it in aluminum
    foil? Won't it block whatever from reaching the glass? I heard it is
    the UV that will clear the glass. Well, it won't hurt anything if it
    doesn't work.
     
  8. Sorry, I missed the words "leaving the glass exposed".
     
  9. Hi Dave, I think there has been confusion in this thread regarding the phenomenon that you are seeing.

    You state in your original post: "The yellow cast of the lens is really a reflection of light from the front glass". If the yellow colour you describe is merely a reflection and is not visible in transmitted light, then there is no problem at all. The colour cast of the light reflected from the elements of many Super Takumar lenses that I have seen is indeed an amber colour. This is the colour imparted to reflected light by the anti-reflection coating that pre-dated the Super Multi Coating (later abbreviated to SMC) that was introduced around 1971. It's normal.

    The other phenomenon that you mention is yellowing of the glass due to radiation damage. As noted above, radioactive oxides of uranium and some rare earth elements were added to create glass with higher refractive index for a few of the faster lenses - famously the original 50mm f1.4 and 35mm f2 - and not the 55mm f1.8 (not 50mm f1.7) that you have on your SL. This coloration is visbile only when you examine light transmitted through the lens. To test for this, hold the lens over a sheet of white paper. But from your description, I don't think you have it at all.

    Rod
     
  10. "This coloration is visbile only when you examine light transmitted through the lens."

    Rod, thanks a lot for your post. I indeed have the 55/1.8, not 50/1.7.
    I also have a Super Takumar 50mm/1.4 that looks just like my 55/1.8.
    I did look at the reflection of the front element of the lens and see
    a very obvious yellow (or amber) reflection from the entire surface.
    I tried to look through the lens pointing at the sky it's not crystal
    clear but it is not as yellow (or amber) as the reflection.

    I also have a Super Takumar 200mm/f4. The reflection is quite colorless. It is obvious to me that it has no yellowing glss in it.
    I also have a 135mm/3.5 that is a SMC Takumar. It looks just like the
    200/f4, no yellow glass either.

    I tend to believe that my 55/1.8 and 50/1.4 Super Takumar have yellowing glasses. I will do an experiment. I happen to have a Pentax
    to Yashica/Contax mount converter ring. I will mount the 55 and 50
    Pentax lenses to my Contax which has a few frames of film remain in
    it. I will shoot a Macbeth color card then I will compare against
    my Contax 50/1.4. I will use a transmission densitometer to see if
    there is a subtle yellow cast on the images from these Pentax lenses.
    I can scan the film and use Photoshop to read the colors too. I will
    post the result when it is done in about 2 weeks.

    Dave
     
  11. Hi Dave again,

    Well, I don't think a densiometer is necessary. If you place white paper on a surface and hold the lens just above the paper and observe the color of the paper through the glass, you won't need anything other than your eyes to tell that it is yellow. But is it?

    Forget the reflections. That's nothing to do with radiation damage. Antireflection coatings are thin films of magnesium fluoride and similar compounds deposited onto the glass surface (in a vacuum evaporation process) to induce destructive interference between the incident and reflected light and reduce (ideally cancel) the reflected light. Each layer can only deal with a single specific wavelength of light. The exact color of the light reflected from the coating is a function of the exact thickness of the film. Early coatings were a just one or two layers and aimed to cancel one or two wavelengths of light. Those coatings often reflect purple or amber. Later coatings such as Pentax's SMC and Zeiss T* and others? are seven layers - one for each wavelength of light (I presume).

    I have seen amber and purple colored reflections from Super Takumar and Takumar lenses - but that has nothing to do with the color of the glass itself. (Some late Super Taks actually received SMC before the ring ID was changed. But that's another story!)

    By the way, you don't have a UV filter on either lens, do you? That will impart a straw (pale yellow) color to light transmitted through the lens (hold one over a sheet of paper to observe this).

    Regards, Rod
     
  12. Hi Rod, you have posted some very interesting information about lens
    yellowing. I just did what you suggested but instead of looking at the
    light projected on the paper I look through the lens at the paper.
    I found that my 55mm/1.8 is indeed different from my 50mm/1.4.
    It appears no color when looking through the 55mm/1.8 at my white
    paper. But my 50mm/1.4 indded shows a slight yellow tint. I did a side
    by side comparison and the difference is clearly visible. If I look
    at the projected light on the paper one is brighter than the other
    (f1.8 vs. f1.4) and I think the 50mm/1.4 has a very slight
    yellow tint too but not as subtle as it is also brighter.

    I am glad that my 55/1.8 is OK. This is the one that came with my
    Pentax SL. I had years of very sharp black and white images from it.
    I also had many years of beautiful color images from it after I
    switched to color.

    I have not shot even one frame from the 50/1.4 yet. I got it cheap
    a few years ago and have not used it even once. Funny indeed.

    Thanks a lot again for the helpful information, Rod.

    Dave
     
  13. Dave,

    I think the golden color of the lens is just the color of the lens coating. Before the advent of multicoating, a lot of lenses had a coating with a golden reflection. Before me lies a 1973 photo magazine
    with a lot of advertisements showing lenses with golden reflections.
    Also, my 1971 Nikon 50mmF1,4 has a "golden" coating (from day 1).
    From memory I know that a Pentax Spotmatic with a 50mm lens had at that time had a golden color.
    So I think it's perfectly normal.
    Like a previous poster I think you only have to worry when looking through it to white paper, see a non-white.

    Greetings, Leen van de Klippe
     
  14. Reading it back, I think there was multicoating at that time, just different and not as elaborate ("super"/ 7 layer) as nowadays.
     
  15. I think I am able to confirm that my 55mm/1.8 has no lens yellowing
    symptom. Instead of looking at the reflection, looking through the
    lens pointing at a white paper or white window really tells the truth.
    Side by side comparison with my 50mm/1.4, unfortunately the 1.4 appears
    indeed slightly yellow. Leen, you are right about the golden reflection
    of front element of my leses. For my 55mm/1.8 that's indeed not an idicaton of lens yellowing.

    I'll still proceed to do my color target testing. I got a feeling
    that the effect of yellowing can be corrected by photoshop. I will
    post a result here in a week or two.

    Thanks again for all the input from everyone.

    Dave
     
  16. I have a Super Multi-Coated Takumar 105 2.4 and it was very yellow looking through and at it. I placed it on a window sill for a month (not too much sun in UK this year) and it is now clear.

    Great Fix.

    AB
     
  17. The response and solution to this problem is in a thread in Photo.Net available here: <http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=009X3q>
     
  18. I have the same problem on a mint 2/35 mm Super Takumar. I am going to try the "sun solution", but I would like to know on which side of the windowsill I have tu put the lens (must be outside or not). I am in Belgium and sun is often replaced by rain...

    Thank's a lot to everybody.
     

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