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Lens field of view on M43 bodies - please clarify

Discussion in 'Olympus Cameras' started by thenextpage, Apr 9, 2015.

  1. thenextpage

    thenextpage Mu-43 Regular

    89
    Oct 13, 2014
    Hello all,

    I'm searching for clarification on field of view for lenses used on M43 bodies. I own an E-M5 as well as an E-M1. As I understand and is widely known, the FOV of a specific lens doubles on a M43 body from it's focal length - for example, a 75mm lens gives you a focal view of 150mm - as it would be on a 35mm full-frame sensor. I understand this.

    What I'm curious to know is:
    - when compared to a 75mm lens on a full-frame body, does a 75mm on a M43 body give you the same basic image, with the difference being that it's cropped because of the sensor?

    In other words, if I were to take a shot with a 75mm lens on a full frame body - then crop the image to what the image would be if taken with a M43 body; would that cropped image essentially be the same as if it were taken with a 75mm lens on a M43 body originally?

    So, are we actually getting extra length out of a lens when using a M43 body, or is it basically a cropped image of what it would be on a full-frame body? If the latter is true, then no lens exists for the M43 system that provides a length more than 300mm - as compared to what would be achievable with a full-frame body with cropping.

    I'm not complaining - just curious to know if I understand properly. Thank you!
     
    Last edited: Apr 9, 2015
  2. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    Keith
    I think you've basically got it right.

    Of course the discussion of crop sensors, 35mm "equivalency" tend to spark lots of discussion around these parts. Pretty soon someone will bring up depth-of-field (oops, did I just do that) and the whole discussion will run off the rails. Should be fun to watch. :hiding:
     
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  3. oldracer

    oldracer Mu-43 All-Pro

    Oct 1, 2010
    USA
    It's just cropping. In fact the 2x is sometimes called a "crop factor." If you used that 75mm lens full frame, then cropped that full frame down to M43 size, the resulting image would be approximately what you'd have FF with a 150mm lens.

    There is a little subtlety to it in that the aspect ratios of the sensors are not the same. 3:2 vs 4:3 in the case of FF vs M43. So the crop factor alone doesn't give you a mathematically exact result, but it's close enough for most work.

    Now, having said that it's just cropping, there is a second subtlety having to do with depth of field: The DOF of a lens is the same regardless of what size sensor is behind it. So at the same aperture the DOF of a 25mm M43 lens will be that same as the DOF of a 25mm FF lens, NOT the same as a 50mm FF lens. This is one reason you see all these f0.95 and similar fast lenses becoming available; they provide a shallower DOF for the given focal length and hence find a market with photographers for whom shooting with a shallow DOF is important.

    Edit: I was typing with DeeJayK's post went up. I guess he is prescient!
     
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  4. gryphon1911

    gryphon1911 Mu-43 Hall of Famer

    Mar 13, 2014
    Central Ohio, USA
    Andrew
    2 terms.

    Focal length - what is printed on the lens - a 75mm on an 135 camera is a 75mm on an m43 camera. All things being equal, so are exposure values such as aperture, shutter speed and ISO.
    Field of view - the angle at which you see through the viewfinder.

    Some additional things.

    A crop is when you take a smaller part of an image from the full information from the sensor. An m43 sensor has its full surface area exposed, it's just that since the sensor is smaller the same focal length is concentrated in the central part of the image.

    If we have a 12mp FX sensor and a 12mp m43 sensor, you'll most likely get a better level of detail taking the image at the field of view of the m43 than you would cropping in and zooming into the image to create an equivalent view for both. A general idea, not an absolute.

    Also, 75mm on both lenses are going to have visual characteristics of a 75mm. You don't magically get a 150 depth of field from an m43 camera because the field of view you are seeing is tighter into the center of the scene.
     
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  5. gr6825

    gr6825 Mu-43 Veteran

    277
    Oct 10, 2012
    The focal length of a lens stays the same, even when used across different formats. I think you have the idea about right, but the complexity ramps up quickly when you start trying to determine equivalency across formats.
     
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  6. tkbslc

    tkbslc Mu-43 Hall of Famer

    Yes it is a "crop".

    However saying we gain nothing over just cropping FF images is just not true. Most FF sensors are in the 20-36MP range. Cropping those 2x leaves you with 1/4 the resolution and 2 stops more noise. So that is 5-9MP at effectively 2 stops higher. I guess that new Canon 50MP sensor would leave you with 12.5MP. You also make tracking really difficult as your subject is 1/4 as large in the frame as it would be with the m4/3. It's harder for the AF to keep up and for you to see it. On the body side, I don't know a FF option that can keep up with cameras like the E-M1 that are anywhere near that size.
     
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  7. Growltiger

    Growltiger Mu-43 Top Veteran

    644
    Mar 26, 2014
    UK
    To clear up this point, I have a 75-300 M43 lens. To get the same field of view on FF you would need a 150-600 zoom.

    Taking photos at 300mm (600mm equivalent) handheld with an E-M1 is perfectly possible and easy, and the lens is tiny. Trying to do that with an FF camera and a 600mm lens would require considerable strength.
     
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  8. thenextpage

    thenextpage Mu-43 Regular

    89
    Oct 13, 2014
    gryphon1911, thank you for the excellent response. This really helps me to understand the topic better. And for the clarification on terms as well - I went back and edited my original post to make it align with the proper definitions. I think that with this information, at least for now, satisfies all I care to understand for how a M43 sensor relates to a FX sensor.
     
  9. tkbslc

    tkbslc Mu-43 Hall of Famer

    I disagree. Literally every visual characteristic I can think of will NOT be the same.
     
  10. Klorenzo

    Klorenzo Mu-43 All-Pro

    Mar 10, 2014
    Lorenzo
    I think there is another subtlety: I think that the idea of "crop" began with the first APS-C sensors, where you had a full-frame lens projecting a big image over a smaller sensors. So part of the image was just lost or "cropped".
    With m43 native lenses there is not real cropping: the full image circle is used and you get the "native" field of view for that focal length on this format. When compared to a 35mm lens and sensor you get a tighter framing but with the same perspective so it looks like a crop.

    There is one big difference: if you take even the Nikon 810 and crop it you get a 9 mega pixel image instead of 16MP. A 5d gives you just 5.5MP and even the 5DS stops at 12.5MP.

    To answer your last question there should be a weird Kodak 400mm/6.7 or the "four thirds" 50-200 with 2x TC but yes, the angle of view would be the same of a 800mm on FF, about 3 degrees (diagonal). The upcoming Olympus 300mm with the 1.4x TC will be the longer native lens.
     
    Last edited: Apr 9, 2015
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  11. oldracer

    oldracer Mu-43 All-Pro

    Oct 1, 2010
    USA
    DeeJayK is prescient!
    :popcorm2:
    :drinks:
     
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  12. gr6825

    gr6825 Mu-43 Veteran

    277
    Oct 10, 2012
    LOL
     
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  13. thenextpage

    thenextpage Mu-43 Regular

    89
    Oct 13, 2014
    Sorry oldracer but I'm new and don't understand - can you please explain to me what it means that DeeJayK is prescient?
     
  14. tkbslc

    tkbslc Mu-43 Hall of Famer

    I disagree. :p
     
  15. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    Keith
    Go back and read the thread from the top, particularly the second and third posts.
     
  16. gryphon1911

    gryphon1911 Mu-43 Hall of Famer

    Mar 13, 2014
    Central Ohio, USA
    Andrew
    You are just disagreeing with EVERYTHING today! lmao :friends:
     
  17. thenextpage

    thenextpage Mu-43 Regular

    89
    Oct 13, 2014
    Ha OK I get it. Sorry it took me a minute; I had to look up the definition of "prescient". You are prescient!
     
  18. tkbslc

    tkbslc Mu-43 Hall of Famer

    No I am certainly NOT!!

    :hide:
     
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  19. Speedliner

    Speedliner Mu-43 All-Pro

    Mar 2, 2015
    Southern NJ, USA
    Rob
    Clear as mud. Thought DOF was NOT equal and that m43 created a wider DOF than larger sensors - given same FL and Aperture.
     
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  20. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    Keith
    This isn't my first rodeo. :p