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DOF: FF vs APSC vs m43

Discussion in 'Open Discussion' started by daum, Jan 18, 2013.

  1. daum

    daum Mu-43 Veteran

    Aug 26, 2011
    Hi, I just want to know if anyone has done tests to see how big the difference is in bokeh between FF, APSC, and m43 sensors.

    I currently have an OMD, EP3, and D7000. I want to ditch the D7000 but I already have an 85 1.8 that i would like to keep for portraits only. Would it be worth it to keep it only for portraits on the rare occasions that i do take it out?

    I may consider the 75mm 1.8 IF the bokeh matchs that of the APSC sensor. Thoughts?
  2. meyerweb

    meyerweb Mu-43 Hall of Famer Subscribing Member

    Sep 5, 2011
    Bokeh is a product of the lens, not the format. It is NOT the same thing as DOF. Two lenses with the same focal length and f-stop can have radically different bokeh.

    If you really mean DOF, there are probably 50 threads about that here. In short, given the same angle of view and f-stop, m43 will provide the equivalent DoF of a full frame lens set two stops smaller. Compared to APS-C, the difference is only about 2/3 stop. So the 85mm lens set to f/1.8 on your Olympus will have approximately the same DOF as if it were set to f/2.2 (more or less) on your D7000. Not a huge difference.

    Also, understand that DOF has nothing to do with the format the lens was designed for. An 85mm f/1.8 lens on a m43 body will provide the same DOF whether it was designed for m43, APS-C, FF, or a 4x5 view camera. So the 75mm f/1.8 and 85mm f/1.8 lenses will have very similar DOF used on your Olympus bodies. In fact, if you shoot from the same position, and crop the 75mm shot to match the FOV of the 85mm lens, they will have identical DOF.

    Bokeh is a different story. The only way to know for sure how the bokeh compares is to, well, compare them. Shoot the same subjects, from the same location, at the same apertures, and look at the images.
    • Like Like x 4
  3. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    What he said. Excellent and concise answer.

  4. fransglans

    fransglans Mu-43 All-Pro

    Jun 12, 2012
    Just a tiny problem, the OP may not have the oly 75 to compare with his 85 1.8...And therefore he asked if someone may have done this bokeh comparison..
  5. jloden

    jloden Mu-43 Hall of Famer

    May 15, 2012
    Hunterdon County, NJ
    I'm not sure if you're asking for a direct comparison between the two lenses on their respective sensors, or if you're just asking if the 75mm can give you nice shallow DoF for portraits.

    If it's the latter, I think we can safely agree the 75mm is capable of some very nice shallow DoF, background-melting portraits. Take a look at the 75mm Image Thread for plenty of examples, both portrait and non portrait photos.
  6. daum

    daum Mu-43 Veteran

    Aug 26, 2011
    Sorry for the confusion guys. Basically what i wanted to see is the effects of the 2/3 stop on bokeh between sensor sizes of lens with the same focal length.

    I don't really want to keep the d7000 kit just for slightly creamier bokeh. if there is a difference at all.
  7. It's a well established fact that for lenses with the same angle-of-view on their respective formats and shot at the same aperture, depth-of-field will reduce as format size increases i.e. m4/3 -> APS-C -> FF

    The thing with shooting portraits is that you have a lot of control over the photographic process. You position the subject, you choose the background, you choose the direction of light (or add your own). Super shallow depth-of-field will allow you to position a subject in front of just about any piece of crap in the background and blur it out, but by taking a little bit of care with the different variables you will still get wonderful portraits with a smaller format like Micro 4/3.

    If you're talking about the quality of the out-of-focus areas (smooth or harsh) then that is more down to individual lens design.
  8. jloden

    jloden Mu-43 Hall of Famer

    May 15, 2012
    Hunterdon County, NJ
    Having taken some portraits at the local dog park with the 75mm f/1.8 I can in fact confirm that it will blur out just about any piece of crap in the background :biggrin:
    • Like Like x 1
  9. WT21

    WT21 Super Moderator Subscribing Member

    Feb 19, 2010
    Once more as mentioned, though, creamy bokeh is a product of the lens. The amount of out of focus is related to the DOF (and sensor size and aperture). You can have very nervous bokeh on full frame, and you can have creamy bokeh on m43. The lens will drive that, not the sensor. But the DOF to full frame is naturally shallower at the same f/stop.

    If you put the 85/1.8 on your D7000 and shoot at 1.8, and then another shot at 2.5, you can APPROXIMATE what the DOF might look like if you were shooting a 63mm lens at 1.8 on m43.

    I think your REAL question is (looking back at your first post) -- can you replace your D7000 + 85/1.8 with buying the 75/1.8 to go with your existing m43 camera. My suggestion: Rent the lens from lensrentals.com, and try them both out together. Even if someone had samples of both to post, you'll get a much better understanding if you like the lens if you try them side-by-side, and then would feel more comfortable in your decision. Just my opinion, but I've really gotten into renting gear before buying.
  10. Good to know. If I ever choose to use actual pieces of crap as my background I'll look no further than the Oly 75!
    • Like Like x 1
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