Zeiss Loxia 21mm f/2.8, another good reason to go with Sony A7 cameras!

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8 Responses

  1. Mike Aubrey says:

    In fairness, the distortion for the Milvus 21mm f/2.8 is still worse.

  2. Hi Mike,
    I agree, my remark was rather toward software corrections part of recent lens design. That would imply other questions, such as how MTF respond to the software correction e.g.
    Anyway, for most people out there, it is a good thing.

    Cheers,
    Viktor

  3. Mike Aubrey says:

    Agreed!

    The other nice thing is that it looks like the distortion on this new lens is more barrel than mustache, too!

  4. jim kannry says:

    Hi Viktor,
    Not knowing much about lens design, I can’t understand how the new Loxia 21mm is so much more compact, especially considering filter diameter, than the Distagon ZF Nikon mount 21mm equivalent (which, by the way, I think is a great lens). Does this imply anything about a future telephoto lens also being much more compact, or is there something in the E mount design that enables smaller wide angle lenses but not telephotos?
    Regards,
    Jim

    • Hi Jim,
      without going deep into theory, the reason is rather simple… Long focal length lenses are usually at least as large (long) as their focal length indicate – 100mm lens will be approx.100mm long, 500mm lens will be approx. 500mm long. (If you want to be able to focus on infinity) This is physic and we can’t really change it…

      Sony E mount with its very short flange distance, can benefit at wider focal lengths, which are not limited by physics (at least not by focal length), but as the focal length starts to grow, advantage of short flange distance is fading.

      There were few attempts to make smaller telephoto lenses, mainly with so called “mirror” lenses (catadioptric), which are using mirror inside the lens to cut its physical length (light rays are reflected like in the mirror labyrinth in order to preserve their intended length). Mirror lenses are often used in telescopes, but you can find also many in photography.

      They were kind of popular in 80′ not so much today. Disadvantages of those lenses are mainly slow speed (lot of light is lost in those reflections), they have very nervous so called “donut” bokeh, loss of contrast is also very problematic, etc. You can buy 800mm f/8 by Samyang – http://www.amazon.com/Rokinon-Teleconverter-Cleaning-Digital-Cameras/dp/B0050K2X3W for less than 200 USD, but don’t read reviews 🙂

      Canon is also experimenting with the diffraction optics, another “technology” how to alter light rays refraction and allow smaller telephoto lens construction (while correcting effectively aberrations). I was very enthusiastic about this technology, but it seems that it isn’t really popular today. (One of the reason is the expensive production of diffractive optics.)

      We shouldn’t also forget that with the evolution of sensor technology and resolution, as well as non linear, progressive software image calculations and pixel interpolation, we already achieved significant progress. If you switch your Sony A7r II in APS-C mode, you will already make 150mm out of your 100mm lens at whooping 18mpx. Going further you can crop even 200mm FOV equivalent at still respectable resolution. (You can do the same in post processing of course by simply cropping your image).
      If you enlarge your image using deconvolution or similar methods, you can crop even more and improve resulting IQ quite a lot (in some situations).

      All in all, I believe that the size (in terms of length) of telephoto lenses will decrease one way or another, but then we have to deal with the speed – amount of light, or aperture and front element diameter relation and that is another wall which physics built in front of us 🙂

      If you want to learn more about lens construction and design limits, there are tons of sources on the Internet, for the beginning I would suggest great article from Cambridge in color – http://www.cambridgeincolour.com/tutorials/camera-lenses.htm

      Cheers,
      Viktor

      • jim kannry says:

        Hi Viktor,
        Thank you for pointing me to the Cambridge in Color web site. Very informative. Well worth understanding the theory behind what I’ve been trying to use for so many years.
        I must say I am more impressed with the new Loxia 21mm which is specially designed for Sony than I am with the new Milvus 28mm which is more of a very high end dslr mount design. If lens size, weight, and price are eliminated from consideration, designers should be able to provide state of the art . But hats off to Zeiss for also considering size and weight as important factors for Sony mirror system users. Maybe a smaller market at present, but surely growing rapidly, thanks in part to excellent reviews from you and others.
        Regards,
        Jim

  1. December 18, 2015

    […] my previous Loxia 21/2.8 announcement article – Zeiss Loxia 21mm f/2.8, another good reason to go with Sony A7 cameras! you will find most technical details. In this review, I will focus more on field usage and some […]

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