Not what I expected

Discussion in 'Adapted Lenses' started by oxhouser, Feb 11, 2015.

  1. oxhouser

    oxhouser Mu-43 Regular

    Nov 26, 2012
    Just picked up a cheap Minolta 50mm f1.8, everything I have read indicated I would get somethi g close to 100mm lens when fitted on m4/3 I even checked out FOV simulators which again gave close to half the angle of view as you would expect
    In reality the view I get from my m4/3 60mm is almost identical to the view I get on the adapted 50mm, is this common? Do different lenses of same focal plane give different FOV
    I can't find any real information for calculating this properly, I'd really like to draw this out in cad but can't find the critical dimensions to map it out
    Just interested in what's going on and if anyone can add to this
  2. edmsnap

    edmsnap Mu-43 Veteran

    Dec 20, 2011
    Edmonton, Alberta
    Why would a 50mm and a 60mm lens give vastly different fields of view? They'll give the same FOV as a 100mm and 120mm lens on full-frame respectively.
  3. OzRay

    OzRay Mu-43 Hall of Famer

    Jan 29, 2010
    South Gippsland, Australia
    Ray, not Oz
    Stated and actual FL can differ, sometimes quite substantially, and you never know what you get with adapted lenses.
  4. Vivalo

    Vivalo Olympus loser Subscribing Member

    Nov 16, 2010
  5. T N Args

    T N Args Agent Photocateur

    Dec 3, 2013
    Adelaide, Australia
    call me Arg
    Hello. I think you misunderstood what is going on. The 50mm Minolta lens will give exactly the same diagonal FOV on your m43 camera as a 100mm lens does on a full frame camera.

    And your 60mm m43 lens is giving you a FOV like a 120mm lens on a full frame camera.

    Any two lenses with the same focal length written on the lens will always have the same FOV when put on the same camera -- it doesn't matter what camera it came from.
    • Like Like x 4
  6. agentlossing

    agentlossing Mu-43 Hall of Famer Subscribing Member

    Jun 26, 2013
    Andrew Lossing

  7. tosvus

    tosvus Mu-43 Top Veteran

    Jan 4, 2014
    While true, I think T N Args & edmsnap, explain what OP is missing. Regardless of whether it is a full frame lens or a native m43 lens, you need to double the number to get FF equivalent focal length, so 50 & 60 turns into 100 & 120 respectively.
    • Like Like x 2
  8. barry13

    barry13 Super Moderator; Photon Wrangler Subscribing Member

    Mar 7, 2014
    Southern California
    A 50mm lens is a 50mm lens on any camera you put it on.

    The FoV is dependent upon the sensor size of the camera you're using, and has nothing to do with the mount on the lens.

    • Like Like x 1
  9. pellicle

    pellicle Mu-43 Hall of Famer

    Feb 10, 2010
    Southport, OzTrailEYa

    No, it will give you (read this next word twice) effectively what a 100mm gives you on a full frame camera when mounted on a 43rds camera.

    So, compared to what images made with thal lens would look like on a full frame camera it is capturing effectively 100mm would capture on full from with it mounted on the 43rds...

    Your 60mm lens is effectively a 120mm

    What you have missed is that 50mm is 50mm and when compared to 60mm is less wide (PS: I mean that the 60mm takes a less wide view ... oh well).
  10. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    An adapted 50mm lens and a native Micro 4/3 50mm lens give the same FOV on a MFT camera.
  11. WT21

    WT21 Mu-43 Legend Subscribing Member

    Feb 19, 2010
    What others have said -- effective focal length/FOV can vary from lens to lens regardless of what is stamped on it, and apparent FOV can change even with focus.

    For example, the Olympus 25mm lens is know to have an actual FOV that is wider than the Panasonic 25mm lens, even though both are design for m43.

    Look under "general observations" in Robin Wong's review of the O25 here:

    btw -- you will also find out that sometimes apertures aren't all the same, either, even at the same f/stop on two lenses from different manufactures, but that are marked as the same focal length.

    Embrace the variability! :)
  12. barry13

    barry13 Super Moderator; Photon Wrangler Subscribing Member

    Mar 7, 2014
    Southern California
    The variability between lenses has nothing to do with what the OP is talking about. He expected the 50mm ('full-frame') lens to work like a hypothetical 100mm mu-43 lens.


    BTW, I really think it's counter-productive for us (mu-43 users) to frequently speak of lenses 'equivalent focal length'; it is very confusing to those new to photography, and only seems useful to those who frequently switch formats.
    Even if someone is buying a legacy lens, the FF equivalent FL is irrelevant if they are only used to mu-43.

    I have shot 35mm film in the distant past, but mu-43 is my 'native' system now, and when someone mentions a 50mm lens, I think of it in terms of what FoV it would give on mu-43. If they are talking about some other system, e.g. FF, then I convert 50mm to 25mm, and realize on FF that the 50mm would be just like a 25mm on mu-43.
    I realize this is backwards from how many of us talk about lenses, but that is my point... someone not used to FF will not be thinking that way!

    • Like Like x 1
  13. demiro

    demiro Mu-43 Hall of Famer

    Nov 7, 2010
    If you look beyond this forum the majority of folks talking about this sort of topic are still shooting APS-C. Many, especially lately, are also shooting FF. Those folks all talk in FF equivalence. We are very much in the minority. Makes sense to me that we relate to the general photography community, rather than doing our own thing just in m4/3s-world.
    • Agree Agree x 1
  14. agentlossing

    agentlossing Mu-43 Hall of Famer Subscribing Member

    Jun 26, 2013
    Andrew Lossing
    I think the OP needs to clarify what he is asking.
  15. barry13

    barry13 Super Moderator; Photon Wrangler Subscribing Member

    Mar 7, 2014
    Southern California

    I'm talking about discussions within other threads in, not when we are relating to the general photography community.

    If I'm talking (in person) to other photographers, and they ask what lens I'm using, I'll tell them the FL, and the FF equivalent if they're not familiar with mu-43.

    But here, unless we're comparing systems or a new user is asking or confused about FL/FoV, then it's pointless to talk in terms of equivalent FL.

    I can link to examples of such posts if you like (as I come across them; there are many).

    (If you are saying that a lot of users here use multiple systems, they still don't need to mention equivalent FL when talking about mu-43 here.)

    Here's a really confusing thread; a large percentage of the posters don't seem to have a good understanding of the issues and are adding to the OP's confusion:
    For example, one user says that a 24mm legacy lens with a speedbooster would be equal FL/FoV to an mu-43 12mm lens. I don't think that's right for most (all?) focal reducers.
    However, that thread started with the OP asking about FF lenses and FL, so I can't say that it's a perfect example.

  16. oxhouser

    oxhouser Mu-43 Regular

    Nov 26, 2012
    Thanks people don't get me wrong I'm not bothered or in anyway upset by the results just surprised by what I got
    I think I understand what your saying, would it not be better to refer to adapted lenses by focal length F number and FOV
    If reviewing an adapted lens why not set the camera at 4 meter (for example) from a wall and report how many meters either side of centre is in view, would that not help people select the correct lens?
    Just a thought

    Sent from my iPad using Mu-43
  17. DigitalD

    DigitalD Mu-43 Top Veteran

    Jan 10, 2014
    I disagree. Its not pointless because if you are learning photography you should understand this very simple concept. No matter how confusing it is in the beginning. It's good to understand what the FL is and how that pertains to its f-stop and judging DOF and what smaller crop sensors do to your image. Because if these beginners go and get a photography book that tells them that a 90mm lens is the best for portraits and get one for their M43, they will be frustrated like Oxhouse here and not understand why they have to stand back 20 feet to photograph their subject.

    Don't worry, This question comes up a lot. The reason why lenses don't show a 'equivalent' focal length is because the focal length is based of the physics of the glass itself and the camera industry (as well as photographers) needed a standard so it was decided it would be based on 35mm film, the most popular film format in history. What you are not understanding is that the sensor crops into the image changing the Field of View therefore SIMULATING a longer focal length based on your camera's crop factor. See image below.


    So on a M43 sensor your crop factor is x2. That means you need to double the advertised focal length of the lens x2. This goes for any lens INCLUDING m43 lenses because all lenses always show their actual focal length based on the historical 35mm film format, not their mount type.

    APS-C sensors generally have a crop factor of 1.6x. So your 50mm lens will act like a 80mm lens on a APS-C camera.

    So if companies changed their advertised focal length based on the sensor it was made for there would actually be more confusion. For instance Canon makes both APS-C sensors and Full frame sensors with the exact same EF mount. APS-C photographers simply have to do a little math to judge how that lens will behave on their camera. So in the end having a standard measurement for Focal Length on lenses makes it easier for photographers of different sensor sizes to understand how that lens will behave on their camera.

    Make sense now?
    • Like Like x 3
  18. alan1972

    alan1972 Mu-43 Top Veteran Subscribing Member

    Jun 23, 2012
    Malaga, Spain
    Alan Grant
    I am wondering why you suggest that for adapted lenses in particular? The field of view is not affected by whether a lens is adapted or not. As it happens there are no native lenses with a focal length of exactly 50mm as far as I know, but any 50mm lens adapted to m43 will be a little narrower than the native 45mm lenses and a bit wider than the native 60mm lenses.

    I agree with barry above that it sometimes seems that FF equivalents are overused to the extent they increase confusion rather than clarifying. I understand that they are sometimes necessary when comparing different sensor sizes, but they seem to be used frequently even when m43 is the only system being discussed. In this example where you already have a roughly similar m43 lens to compare with, converting 50mm to "100mm equivalent" tells you less than simply comparing 50mm to 60mm directly.
    • Like Like x 1
  19. I confess to also having been confused upon entry to the m43+adapted lens world, in fact, it wasn't until I directly compared my adapted 50mm to my p45-150 set to @50mm before I fully grokked it.
  20. AussiePhil

    AussiePhil Mu-43 All-Pro

    Jun 1, 2014
    Canberra, ACT, Aust
    I don't get the issue, crop factor is 2x.... just multiply any numbers on any lens native or adapted by 2x to get the standardised FOV length.

    45mm x 2x = 90mm FOV
    50mm x 2x = 100mm FOV

    add a focal reducer into the mix the maths may need a calculator but is no harder

    actual FL x crop factor x focal reducer factor
    50mm x 2 x .74 = 74mm FOV

    We do it all the time when talking tele convertors yet fail to be able to do it when not.

    Maybe I'm just a dinosaur of the film world but I do this on the fly based on the numbers on the lens.

    I believe it is important for newbies to FULLY understand the AOV/FOV of their chosen format and lens combination. This was brought home by an intelligent newbie I was helping out that after shooting some wildlife that she couldn't get close enough to with a 40-150 was bemoaning the fact she only had 150mm whereas she knew a lot of others that had 70-200 lenses in other formats. It took a little careful explaining that she actually had more reach than many others before she understood that she just wasn't close enough.

    We have FOV reach that most users of other formats can only dream about and yet people whinge that we don't have a native lens longer than 300mm.
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