Asahi Super Takumar 50 f1.4 – Legacy 50mm. Which one is the best? Part 4

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13 Responses

  1. Anonymous says:

    nice idea.. thanks for posting..

  2. Joe Pickens says:

    Dear Victor: I really enjoy your reviews. I have 9 Pentax 50 or 55-mm MF lenses including a Super-Multi-Coated 50/1.4 I bought today that I have not yet used. I did do extensive testing of my takumars using the SONY-NEX-7 vs. other “normal lenses”. The overall “winner” was the Canon FD 50/1.4 (I have two specimens) with my results qualitatively similar to yours. My two 50/1.4 Supertakumars were a bit disappointing at f1.4, albeit one of them has some internal spider web fungus. I intend to do additional tests when I have time. I am unfortunately not nearly as skilled as you on a computer. Joe Pickens

    • Hi Joe,
      I am glad that we share experience about Canon FD. I learned by time, that actual condition of those legacy lenses is often more important for their performance than their original optical design. There are so many anomalies that can occur with the glass during years that it is really hard to make any conclusions related to original lens performance. Those Canon FDn are younger than Super Takumars, so they might be simply better preserved.
      On the other hand, we are getting new toys with those old glasses, as original as their own history might be 🙂

      Thank you for visiting us and have a great day,

  3. Petr says:

    Dobrý den,
    sháním světelnou padesátku pro focení za nízké hladiony osvětlení na Sony A7. Nemáte náhodou, prosím, zkušenost, která verze Takumaru je nejlepší, případně i padesátka jiné značky.

    Mnohokrát děkuji za odpověď

    • Zdravím,
      U Takumaru bude především rozhodovat stav. Nejostřejši by měla být SMC verze, případně první Pentax verze s označením SMC (ale ne i M). Taktéž první verze Takumaru (8 členu) může být o trochu ostřejší a hlavně je bez radioaktivity.
      Mohu doporučit Canon FD 50/1.4 , poslední, černou verzi (new FD nebo FDn). Velmi ostrý je i starýTopcor 58/1.4 RE, nebo Zeiss Ultron 50/1.8.
      Spokojen jistě budete i s Zeiss Planarem 50/1.4 či levnějším 50/1.7 oba v bajonetu Contax Yashica (C/Y).
      V zásadě platí, že u těch starých objektivů, stav hraje větší roli než jejich konstrukce.

      S pozdravem,
      P.S. Pokud byste měl navazující otázky, založte prosím odpovídající vlákno na našem föru. Místo pod články je omezené pro komentáře a není proto vhodné pro dizkuse. Předem děkuji.

  4. Petr says:

    Děkuji mnohokrát

  5. Stoli89 says:

    I placed my Super Takumar 50/1.4 (7 element version) front down(without filter) on a small mirror, with a cheap IKEA LED desk lamp (the $15 dollar bendable model with base clip). After 2 days under this intense light, the yellowing was gone. Good news, LED does not emit much heat toward the lens…and it’s cheap and fast. I found this approach within multiple sites on the web. Was unsure of the lack of UV from the LED would be a problem…it wasn’t.

    My M4/3 white balance did not require this treatment…I was more concerned with the slowing down of a fast spec’d lens(by up to 1 full stop) due to the yellowing. Problem solved.

    As an aside, the Thorium Oxide is not in a coating on these Pentax lenses, but homogeneously (up to 30%) contained within one element. ThO2 is favorable because it has a high refractive index with low light dispersion, allowing for more compact designs with less “curved” (more costly) elements. Thorium has a VERY long half-life (over 14 Billion years) and decays by Alpha particle emission. Alpha’s have very low kinetic energy but are highly charged (+2); essentially Helium nuclei stripped of electrons. They are stopped by the dead human skin layer…so shielding by camera/lens metal, plastic, clothing, other glass elements (etc.) and/or distance makes them essentially harmless. The danger is when the glass is in close proximity to one’s eye surface. Here, the organ is directly exposed and poorly shielded from the effects. Hence why the use of ThO2 in eyepieces was banned long ago. Of course, Alpha particle ingestion is bad because the Thorium could concentrate in an organ susceptible to Alpha radiation. Highly unlikely as this would require one to grind the lens into fine dust and then ingest. Under normal uses, Thoriated camera lens glass is a non issue. Just my opinion as a nuclear engineer and former Chemistry and Radiological Controls (CRA) officer on a nuclear submarine.

    • Dear Stoli89,
      if we would have prize for the best and most useful comment ever, you’ll be among top candidates with this post. Thank you for great suggestion with LED lamp and for your opinion about radioactivity risk. I admit, that your thorough explanation sounded a bit like Sheldon’s monologue from Bing Bang Theory to me, but your conclusion is clear and bold 🙂
      All the best and thank you again for valuable input!

      • Stoli89 says:

        Thanks for the feedback. As an aside, I did ask Sheldon why these lenses darken over time. What is the root cause? According to him (:P), this is not especially due to the irradiation of coatings, cement or glue. It’s the glass itself…specifically the glass element in which the Thorium Oxide is homogeneously present. Within the element, the ionizing radiation causes defects in the chemical bonds with the glass. These defects introduce new wavelength absorptions (i.e. darkening of glass). The defects will RECOVER over time if the ionizing source is removed. However, since the ThO2 is homogeneously present in the structure, an equilibrium will be reached. The higher the concentration of the ThO2, the darker that eventual equilibrium. High intensity light accelerates the RECOVERY of these defects. However, the lens will gradually trend (darken) back toward equilibrium in between “RECOVERY” treatments.

        Sheldon can be a bit “thorough” sometimes.

        PS: This is also why thick lead glass viewing portals in the secondary containment wall of a nuclear reactor may tend to have a slightly darkened tinge to them over time. Assuming you actually wanted to know this.

        • BAZINGA!!!!

          Thanks Stoli89, really appreciated. There are not many reliable info on radioactive lenses and it usually ends with those who are saying “It’s dangerous, why risking” and those who says “we are exposed to more radioactivity by one flight that using one of affected lenses whole year”. I am glad your comments are putting things in better perspective, maybe I will include them in a regular post, once I get back to legacy lens testing.

    • Matteo Pastorino says:

      Thx for clarifiyng, really appreciated

  6. Tony Belding says:

    The one mystery that remains in my mind about radioactive lenses is whether the yellowing also has any effect on the refractive index of the glass. If that were the case, it might explain why the corners were not great on a yellowed specimen. I’ve seen some speculation about this, but I’m not aware of anybody who has tested it.

    • Hi Tony,
      it’s not such a mystery in fact. Yellowing works a bit like vignetting for some wave lengths. In effect, it should cause differences in scene rendering, mainly in the micro and global contrast department. So yes, (absolute) refractive index might be affected, but it shouldn’t have significant influence on SA, nor on other type of aberrations causing image smearing (darkening, color shifts and/or loss of contrast are more probable consequences)
      To test it, we would need optical bench with refractometer, which is too much complex and complicated (and obtained results will be hardly relevant for reference use in particular imaging systems), so I doubt anyone is going to do it.
      For us users, it can be simplified – glass yellowing does affect image quality, especially on digital sensors, but corner smearing (blurriness) shouldn’t be affected by it to the notable level. Color shift and contrast loss might be, to the amount depending on many other factors – scene structure, colors, lighting, distance etc….

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