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Macro question about DOF of µ4/3 vs Full Frame

Discussion in 'Nature' started by Phocal, Sep 23, 2015.

  1. Phocal

    Phocal Mu-43 Hall of Famer

    Jan 3, 2014
    I am having a discussion with someone about macro photography and something came up that I can not answer. I have a Lester Dine 105mm macro lens. If I set focus to 1:1 and take a photo of the same subject with my EM1 and then with say a Sony A7 with both of them at ƒ8............

    1) Will the photos have the same framing or will one capture more or less of the subject?

    2) Will they have identical DOF or will the EM1 have greater DOF?

    Thanks,

    Ronnie
     
  2. Speedliner

    Speedliner Mu-43 All-Pro

    Mar 2, 2015
    Southern NJ, USA
    Rob
    Will be 210mm effective in the EM-1, 105 in the A7, so framing has to be different. DoF should be f16 equivalent as well vs F8, while exposure would still be f8...I think.
     
  3. budeny

    budeny Mu-43 All-Pro

    Mar 4, 2014
    Boulder, CO
    Imagine taking a shot with that lens on A7 and then cropping to the EM1 sensor. Hope you got the answers now.
     
  4. TransientEye

    TransientEye Mu-43 Regular

    136
    Sep 18, 2013
    Barcelona
    Mark
    The images will be identical (ignoring sensor implementation and resolution issues), except that the E-M1 image will show only the central 1/4 of the image on the Sony.

    The lens focal length and aperture are the same, so the only difference is that the u4/3 sensor is just capturing a smaller part of the image.

    Without focus stacking, there is no inherent DOF advantage to u4/3 over full-frame, and usually no image quality advantage for FF over u4/3 (because you are almost always stopped down for DOF). However, the greater pixel density on current u4/3 sensors compared to most (ignore the A7rII) FF sensors means that a 1:1 macro lens on u4/3 usually gives an effectively larger magnification than most FF sensors at 1:1.

    I think the biggest macro advantage for u4/3 has is that you can easily hold a camera and lens in one hand, and an off-camera flash in the other. Doing this with a FF camera+lens is much harder due to the weight...
     
  5. coffeecat

    coffeecat Mu-43 Top Veteran

    708
    Aug 4, 2012
    SW England
    Rob
    • Informative Informative x 1
  6. tkbslc

    tkbslc Mu-43 Hall of Famer

    1) The FF will have twice the angle of view and show 4x the area.
    2) The m4/3 shot will have narrower DOF.
     
  7. gr6825

    gr6825 Mu-43 Veteran

    277
    Oct 10, 2012
    A little OT, but I have an opposite experience. I have a hard time holding small cameras with one hand. One reason I like larger form factor DSLR.
     
  8. wjiang

    wjiang Mu-43 Hall of Famer

    You'll be operating at the same MFD in both cases, so it is just a crop. This has the effect of giving twice as much in your frame with no change in DoF. Alternatively if you back away to give the same framing, you'll get twice as much DoF.
     
    • Agree Agree x 1
  9. wjiang

    wjiang Mu-43 Hall of Famer

    2) Assuming you mean deeper, this only happens if you back away to match framing.
     
  10. tkbslc

    tkbslc Mu-43 Hall of Famer

    If I did that, framing and magnification would be identical, but the M4/3 shot would have significantly deeper DOF, not narrower.

    One of the primary inputs for calculating DOF is the output size. If you just think of the 4/3 shot it as a crop of the FF shot, then you are not holding output size constant and comparison is meaningless.
     
  11. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    I think with macro, taking pixel density into account is hugely important, because you end up getting a different "effective magnification" as a result.

    Take a 16MP shot with a FF Nikon Df and a 16MP shot with an M4/3 E-M5 both using the same lens at the minimum focus distance (i.e. lens max magnification). The M4/3 camera will show you only 1/4 of the frame that the FF camera does, but since they have the same number of pixels, you will effectively have twice the resolution in that area, making your effective magnification greater.
     
  12. Phocal

    Phocal Mu-43 Hall of Famer

    Jan 3, 2014
    • Like Like x 1
  13. wjiang

    wjiang Mu-43 Hall of Famer

    Ah... you're right, I forgot that at macro distances the approximations breakdown... Anyway, see
    http://www.cambridgeincolour.com/tutorials/macro-lenses.htm
     
  14. tkbslc

    tkbslc Mu-43 Hall of Famer

    Actually has nothing to do with Macro, the same would hold true at any distance less than infinity. It's the enlargement factor and crop factor.

    Using the same ACTUAL focal length, a smaller sensor has less DOF at the same output size.
    Using the same EFFECTIVE focal length, a smaller sensor has greater DOF at the same output size.

    We don't compare systems using the same actual focal length very often because usually the resulting images are too different and the comparison is nearly meaningless.
     
  15. Phocal

    Phocal Mu-43 Hall of Famer

    Jan 3, 2014
    Thanks for all the replies. Ok, I get that at 1:1 the m4/3 will show less of the subject. Still not clear on DOF tho. Will dig into more later tonight when I have time.

    Right now I need to get to work on making my lasagna from scratch, including the noodles.

    For DOF at 1:1 will it be same or different?

    For same framing will DOF be same or different?

    Those are still what I am confused on.
     
  16. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    If you hold f-stop and output size constant (equal size prints), the Micro 4/3 DOF will be half the full frame DOF.

    For same framing, you're not 1:1 anymore on Micro 4/3 if you were 1:1 on full frame.
     
    • Appreciate Appreciate x 1
  17. gr6825

    gr6825 Mu-43 Veteran

    277
    Oct 10, 2012
    I would have thought it would be the other way around
     
  18. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    When you hold f-stop and output size constant, the MFT image is equivalent to what you would get if you were to crop the central 25% of the full frame image. To get the same output size, that crop requires greater enlargement and consequently has less DOF.
     
    • Like Like x 1
  19. bikerhiker

    bikerhiker Mu-43 All-Pro

    Dec 24, 2013
    Canada
    David
    Ronnie,

    1, @ 1:1 set distance, the m43 will have a 2x crop factor narrower field of view resulting in an equivalent field of view of a 210mm lens as opposed to 105mm.

    2, Both lens on both cameras will have identical depth of field, because of same lens and same distance shot. However due to the 2x crop factor, the m/43 output will produce a perceived DOF less than that you can achieve with full frame.

    And the reason is simple. Consider this..

    What controls depth of field?

    1, Aperture
    2, Distance
    3, Angle Of View (which is a topic we are discussing now) due to both aperture and distance fixed to get the 1:1 shot.

    All lenses have the same depth of field! Why a wide angle lens has a greater depth of field than a telephoto lens do has to do with this -- the smaller the object is, the more in focus it appears to be and the larger the object the less in focus it appears to be. Since the shot from the m43 is magnified as though it is a crop from a full frame and printed at the same output size, the perceived DOF of the m/43 will be less. How much less depends on the output resolution.

    And the same analogy even with full frame lenses is like this.

    If you shoot with a 28mm full frame lens at identical distance and aperture as the 90mm full frame lens. If you are to crop the 28mm shot to match the field of view of the 90mm and magnify to match output size, the 28mm cropped shot will have an identical DOF as the 90mm full frame lens.
     
    Last edited: Sep 23, 2015
    • Informative Informative x 1
  20. bikerhiker

    bikerhiker Mu-43 All-Pro

    Dec 24, 2013
    Canada
    David
    Actually it is output resolution. There is only 1 focal point in 2 dimensional photography for a fixed focus lens. What you see on paper and monitor screen is in terms of sharpness is the output resolution and how it renders out of focus areas (known as Blur-RAMP) as acceptably sharp or not, but they always have less resolution compared to the 1 focal point. The lower the output resolution, the more sharper the blur ramp perceived to look.
     
    Last edited: Sep 23, 2015