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aperture of non native lenses on m43 camera

Discussion in 'Adapted Lenses' started by winsor, Jul 16, 2012.

  1. winsor

    winsor Mu-43 Rookie

    Apr 21, 2012
    little red dot - city of SIN
    arthur koh
    I am not sure if this have been ask before.

    As we know M43 is of Crop factor of 2.0 as compare to 35mm , thus a greater depth of field.

    My understanding is if I were to fix a native lens of
    olympus 17mm f2.8 lens on my Micro 43 camera, this is similar to a focal length of 34mm F5.6 on 35mm camera

    But What if i were to fix a non native lens for example
    nikkor 50mm f1.8 on my Micro 43 camera. This will be similar to 100mm but what will be the apenture like? will it be 0.95 or will it be 3.5?

    The reason why I am asking is the other day i was trying to take my own photo for passport needed. but the eye in focus but my ears. are far from focus.

    Guys, your input?
  2. Promit

    Promit Mu-43 All-Pro

    Jun 6, 2011
    Baltimore, MD
    Promit Roy
    The equivalence brigade, who are a bunch of idiots, like to confuse this issue quite a bit. It's actually very simple.

    A 50mm f/1.4 is a 50mm f/1.4. It does not matter what you place it on. These are measurements of physical parameters of the lens. The depth of field is exactly what it would be on a full frame camera, but you get less of the image. Thus if you're talking about the ability of the lens to gather light and what it should meter at, the aperture is 1.4. However, the image it produces will be similar to a 100mm f/2.8 on a full frame camera. This is because a 100mm f/1.4 on an FF camera would have very, very narrow depth of field (depth of field is a product of both aperture AND focal length), and the depth of field of our lens isn't affected by the target format. In order to get the same depth of field, we would have to stop down such a lens.
  3. Try this example on different formats using the calculator linked to in the post above. I think that everyone should just play with the numbers on this topic by themselves. The calculator is a great way to understand the subject.
  4. arentol

    arentol Mu-43 Veteran

    Jun 29, 2012
    A lenses focal length is its focal length.
    A lenses aperture is its aperture.
    This is irrespective of the format for which it was designed.
    This is irrespective of the format on which it is being used.

    So no matter what lenses you are comparing, even if one was designed for medium format and the other for m4/3rds, the focal length and aperture would remain whatever they are.

    So you don't need to do any fancy math, a 50 f/1.8 will be a 50 f/1.8, period. If you feel like converting to a 35mm equivalent (which is only necessary if you already are used to thinking in 35mm terms, or are speaking to someone else about lenses in 35mm terms), then do the same thing you would do for the 25... Double it to 100 f/3.6 and you are done.
  5. winsor

    winsor Mu-43 Rookie

    Apr 21, 2012
    little red dot - city of SIN
    arthur koh
    thanks guy, i guess should not be worry too much. and go out and shoot more.
  6. Markb

    Markb Mu-43 Top Veteran

    Jun 9, 2011
    Kent, UK
    Precisely! What changes with the recording format is the field (or angle) of view and the depth of focus. Attempts to quantify this difference just lead to confusion and, even worse, a "proof" of the inferiority of a given format as used by some proponents.

    An f1.8 lens is an f1.8 lens. I'd get into all sorts of trouble if I tried to expose for f3.5 (or even 3.6!!) :confused: 
  7. DeeJayK

    DeeJayK Mu-43 Hall of Famer

    Feb 8, 2011
    Pacific Northwest, USA
    I hesitate to jump into these "equivalency" debates/questions, because I still remain a bit of a newb myself, and they can often get strangely heated, but here goes.

    I'm not sure I agree 100% with the assessment above. Specifically, I have a problem with doubling the f/ number. I do agree that due to the smaller :43: sensor the focal length is effectively doubled when compared to that on a "full frame" sensor/135 film. A better way to think about this is that a 25mm lens mounted on a :43: body will have a roughly similar angle of view (or "field of view") as a 50mm lens mounted on a "full frame" body. It would simplify things quite a bit if we spoke in terms of AOV as opposed to focal length.

    As far as aperture goes, the way I understand it is that the f/ number doesn't change with respect to determining the "correct" exposure. The only reason to double the f/ number is when comparing the depth of field. A 25mm f/1.4 lens on a :43: body will exhibit a roughly similar depth of field (and AOV) of a 50mm f/2.8 lens on a "full frame" body.

    If my thinking is incorrect, please let me know.

    All this said, converting things to "full frame" equivalencies really doesn't have a lot of value IMHO. It might be useful for someone who's coming from a 135 film and is trying to translate the focal lengths he/she is familiar with to a crop sensor ecosystem, but the sooner a user can sort of think in terms of :43:, the better.
  8. arentol

    arentol Mu-43 Veteran

    Jun 29, 2012
    You are correct on every point here. I tried to post fast and simple and made a couple errors. I actually usually try to make the AOV distinction myself, and I am sorry I didn't do so here. I also normally correct others on stating a lens acts like it has half the aperture without specifying that this is in reference to DOF only. I am glad you caught both those things, as I hate to have misinformation floating around, even if it is by mistake rather than intent (because there are enough such people passing it around intentionally!)
  9. pheaukus

    pheaukus Mu-43 Regular

    Jun 22, 2012
    How about we put a sticky somewhere so that whenever this question shows up we can just provide a link? It should be short and easy to understand. The answer should mention DOF distances as well as aperture. Maybe like this:

    Aperture of non native lenses on m43 camera

    Aperture influences both exposure and depth of field (DOF). As regards exposure aperture value will remain the same.
    Depth of field (DOF), which is measured in distance, is affected by by both focal length and aperture.

    When you mount a full frame (FF) lens on m43, both your field of view (FOV) your depth of field (DOF) will be halved relatively to FF.
    Example: 50mm f/2.8 at 20feet. FOV (x-size) on FF is 39°, FOV on m43 is 20°. DOF on FF is 8.57 feet, DOF on m43 is 4.15 feet.

    For the same FOV, choose a lens of half the focal length. At same aperture DOF will be doubled relatively to FF.
    Example: 25mm f/2.8 at 20 feet. FOV on m43 now is 39°. DOF on m43 is 19.9 feet.

    For the same DOF at same aperture, choose about 2/3 focal length. FOV will be 2/3.
    Example: 36mm f/2.8 at 20 feet. FOV on m43 now is 28°. DOF on m43 is 8.26 feet.

    Experiment with this calculator to get a feeling for how it works.

    // Edit: added FOV values to examples.
  10. usayit

    usayit Mu-43 Hall of Famer

    give the hungry food or teach them to farm.

    Take dof calculater and plug in some numbers.... the answer is that easy.
  11. meyerweb

    meyerweb Mu-43 Hall of Famer Subscribing Member

    Sep 5, 2011
    Absolutely agree!

    And I suspect very few people coming to m43 have ever used a FF digital camera. Most are coming from either small sensor P&S cameras or APS-C cameras, so the whole idea of comparing to FF is silly. I think we do it only because multiplying by 2 is so easy.

    But the DOF and FOV difference compared to APS-C (somewhat more meaningful) is much smaller. About 1.3x for FOV, and not quite 1 stop for DOF. So a 25mm f/1.4 exposure on m43 would show FOV and DOF similar to a 35mm f/1.8 shot on APS-C. (Assuming, of course, they're shot from the same location.) Not quite the earth shattering difference the equivalency crowd would like you to think.

    Coming from a P&S the differences will be more dramatic, but in the opposite direction. You'll get much less DOF at equivalent apertures. There are so many different small sensor sizes I'm not going to attempt to quantify the difference.
  12. Arminius


    Jul 12, 2012
    Germany and England
    Sorry for the spanner...

    I am also new to this format and was wondering if any of those calculations help to see if there is a change in relative macro repro ratio?

    z.b. Will my 1:2 ratio macro lens, due to this crop phenom, make it a 1:1 ratio?


  13. dhazeghi

    dhazeghi Mu-43 Hall of Famer Subscribing Member

    Aug 6, 2010
    San Jose, CA
    The reproduction ratio is based on the sensor size (diagonal of sensor divided by diagonal of FoV). So technically it is still 1:2. But it's equivalent in terms of the output to what you'd see from a 1:1 macro on a full-frame sensor.

    Wikipedia has a slightly more detailed description.

    • Like Like x 1
  14. meyerweb

    meyerweb Mu-43 Hall of Famer Subscribing Member

    Sep 5, 2011
    Yes and no. Macro ratios are defined as the relative size of the image captured on film (or sensor) compared to the actual object. So if you take a picture of a dime at 1:1, and then set that dime on it's image on a negative or transparency, it will be the same size.

    The image on the m43 sensor will be exactly the same size as if you exposed on 35mm film and cropped a 4/3 size section out of the middle of the image. So the actual image on the sensor will still be 1/2 life size. So technically the answer is no, it's still 1:2.

    But, you don't generally look at images at sensor size, you look at them on a monitor or print. The amount of your subject captured on a m43 sensor at 1:2 is [more or less*] the same as the amount of your subject captured on a FF sensor at 1:1. Phrased differently, if a 1:1 macro lens captures that dime edge-to-edge on FF, a 1:2 lens will capture the dime edge-to-edge on m43.

    So if both sensors are the same resolution, and you display them both at the same magnification on your monitor, or make the same sized print from both, they'll be basically the same size. So in this sense, yes, the output of a 1:2 macro lens on m43 will be the same as a 1:1 macro lens on FF.

    Confused yet? :smile:

    * I say this because the aspect ratios are slightly different. The comparison is better if you set your m43 camera to capture a 3:2 aspect ratio.
    • Like Like x 1
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