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Lens design - DSLR vs Mirrorless

Discussion in 'Other Systems' started by Danny_SWE, Feb 11, 2015.

  1. Danny_SWE

    Danny_SWE Mu-43 All-Pro

    Apr 30, 2013
    Sweden (Gothenburg)
    I got stuck in a most difficult discussion at work with a DSLR-guy.

    He thinks lenses that are simpler (like ours) are not as good. But then I tried to explain lens design for mirrorless and contrast detect versus for phase detect and mirror. But as I'm no expert I felt I couldn't do it so good. So now I ask you guys...

    What are the actual difference in a lens designed for phase detect and mirror compared to one for more or less and contrast detect?

    (I think I've read something about lens elements for supporting phase detect that you don't need for mirrorless and thus more complicated design but I couldn't find anything when googling)
  2. Conrad

    Conrad Mu-43 Veteran

    What is simpler in mirrorless lenses? The number of elements, use of special glass, and aspherical surfaces is on par with any modern lens design.
  3. tkbslc

    tkbslc Super Moderator

    Phase detect lenses have different AF motors, not different elements. Many new DSLR lenses are being designed to work well for both phase detect and contrast (i.e. Canon STM)

    I'm not sure why one would conclude that mirrorless lenses are simpler designs, though:

    M.Zuiko 12-40 and Panasonic 12-35 have 14 elements
    Canon 24-70 F4 L has 15 elements
    Nikon 24-70 F2.8 has 15 elements

    Olympus 12mm f2 has 11 elements
    Canon 24mm f2.8 has 11 elements

    Olympus 45mm f1.8 has 9 elements
    Canon 85mm f1.8 has 9 elements
    Nikkor 85mm f1.8 G has 9 elements

    I'm noticing a pattern, so I'll stop there.
    • Like Like x 3
  4. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    I would add the new 40-150 too: 16 elements in 10 groups, two AF motors.

    "The optical design features 5 ED (Extra Low Dispersion) elements, one Super ED lens, One EDA (Extra Low dispersion aspherical) lens and one HR (High refractive index and dispersion) lens."

    Ok, marketing talk, but I'm not sure if today there are many DSLR lenses this complex. Anyway more complex design does NOT mean a better lens.

    The smaller distance from the sensor allow to use a couple of lens designs to make lenses of different focal lengths, that is probably the "big" difference.

    And Zeiss is making lenses for mirrorless, maybe those are not as good too. And Fuji, Leica, Olympus are also famous for their toy lenses.
  5. kevinparis

    kevinparis Cantankerous Scotsman Subscribing Member

    Feb 12, 2010
    Gent, Belgium
    Leica rangefinder lenses have always been designed for mirrorless...since 1930 !!... if he thinks Leica or Zeiss or Voigtlander lenses are not good... well each to their own... depends what his definition of good is .

    There is an argument out there that 4/3 and micro 4/3 lenses may HAVE to be way better optically than full frame lenses...the argument being that if you blew the pixel density of the 16mp 4/3 sensor to 35mm full frame.. you would have a 60mp sensor... we will see with the new canon how their lenses stack up resolving that information

    Film was way more forgiving on lenses... light could hit film at any angle and you would get a hit... Digital is a different story.

    think of it as that you were a lens throwing the photons you have captured in the shape of pingpong balls at a target.. lets say a picture frame... in film days, as long as you hit the target you were fine... didn't matter what angle you threw the photon from, it made its mark.

    Digital is different... now the picture frame is full of beer/wine/champagne/shot glasses with their open ends pointing towards you - a megapixel analogy I just made up - bigger glass less mega pixels

    Now try and throw your pingpong ball/photon just where you want it... not so easy now :) 

    • Like Like x 1
  6. Lawrence A.

    Lawrence A. Mu-43 All-Pro

    Mar 14, 2012
    New Mexico

    Does he think a flapping mirror and a pentaprism has anything to do with lens requirements?
  7. John M Flores

    John M Flores Super Moderator

    Jan 7, 2011
    The easiest way to shut up a guy like that is to take better photos than him.
    • Like Like x 6
  8. kevinparis

    kevinparis Cantankerous Scotsman Subscribing Member

    Feb 12, 2010
    Gent, Belgium
    absolutely John :) 

  9. Carbonman

    Carbonman Mu-43 Hall of Famer Subscribing Member

    Jul 10, 2014
    Vancouver BC
    Most wide angle lenses for mirrorless cameras are supposed to be easier to design because they don't have to be retrofocus telephoto designs. If you design a very short focal length lens to focus through a mirror box or similar long distance between the rear element and sensor, a conventional wide angle design needs to be used with the mirror locked up so the element can actually achieve focus at the sensor. A retrofocus design gets around that problem and lets you still have that distance and a swinging mirror.
    If your imaging system doesn't have this kind of restriction, the wide angle lens design can be a little simpler.
    • Like Like x 1
  10. Danny_SWE

    Danny_SWE Mu-43 All-Pro

    Apr 30, 2013
    Sweden (Gothenburg)
    that could be the only thing that actually works :) 

    Thanks guys, now I know a little more for today's discussions :) 
  11. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    I don't think the peak resolving ability of modern lenses is anywhere near the weakest link in the resolution chain. It is more problematic getting them to be consistent, i.e. sharp in the edges and corners when wide open.

    OTOH IMHO the photo enthusiast's task is not to whinge about not getting absolute perfection from equipment, but rather to understand his/her gear and how to use it to get the results he/she needs, e.g. stop down when you need sharp corners. How hard was that? :tongue:
  12. tkbslc

    tkbslc Super Moderator

    That is true, but then remember that the EFL is also HALF of what it would be on FF. So sure, you can design a 25mm lens without retrofocal, but then it's the same EFL as a 50mm on FF, which is also outside the mirror box on a DSLR. A 24mm on FF needs a retrofocal design, but then to get that angle of view we need a 12mm which is way shallower than the m4/3 mount. So its going to be retrofocal too.

    So yes, we get wider lenses in actual focal length, but its no better in terms of effective focal length. There might be some minor advantage vs APS-C DSLR since they have the same mount depth as FF, but have a pretty significant crop factor. But Canon did just figure out how to make a pancake 24mm lens for APS-C, so it's still a pretty small window of advantage.
  13. ManofKent

    ManofKent Hopefully still learning

    Dec 26, 2014
    Faversham, Kent, UK
    More elements aren't always the answer - old Zeiss Biotars and Sonnars can still produce sharp pictures on modern digital sensors. Every air glass interface adds potential problems to a lens designer.
  14. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    Mirrorless means you can remove another mode of failure (the mirror) and probably lower production costs in the process, however the lens design doesn't really change all that much. Having a smaller sensor lowers the coverage requiring meaning you can use more exotic materials or designs which would otherwise be cost prohibitive, however currently only camera phone lenses currently take advantage of it afaik.

    A related side note is the limiting factor in how small cameras can become is really going to be a practical one, if you make them too small things like dust start to have an increasingly large impact (Compare a spec of dust on a piece of 8x10 film to a 1" sensor, on one you might not even notice and on the other it would obscure a huge amount of the sensor).

    In the end it doesn't matter, every lens is capable of generating fantastic output in the right hands.
  15. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    Yes it does, quite dramatically. Designers can allocate more lens correction into software and less into optics with mirrorless, to a degree that DSLR users would not accept because of the distorted OVF image and lack of correspondence between the OVF and the final image.
  16. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
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