Full-Frame vs. APS-C vs. Micro Four Thirds: Depth of Field

One of the first decisions the consumer is faced with when picking a mirrorless interchangeable lens camera (MILC) system is that of sensor size, and the decision typically boils down to full-frame vs. APSC vs. Micro Four Thirds.

While you can get excellent results with all three systems, it is important to take into account a few considerations before diving in and making an investment in a particular ecosystem of bodies and lenses.

When choosing a MILC system, don’t get too caught up on raw specs right away, but consider these two things first:

  1. What are your minimum depth of field needs, and does the system provide lenses to meet them?
  2. What maximum telephoto reach will you ever need, and are you willing to pay for it? This second consideration may be less important for some (myself included).

While crop sensor (APS-C and Micro Four Thirds) cameras look appealing for their size and weight advantages, the difference may not be so great when considering depth of field requirements.

Narrow depth of field: The Great Equalizer

Sony α7 III with Zeiss Batis 85mm f/1.8 lens; Fujifilm X-T2 with Fujinon XF 56mm f/1.2 R lens; Olympus O-MD E-M1 Mark II with Olympus M.Zuiko Digital ED 45mm f/1.2 PRO lens. Thanks to for comparison images.

The image above is an example of what it might take to build a good lens/body combo for portraits requiring narrow depth of field in all three systems: full-frame, APS-C, and Micro Four Thirds, respectively.

Using the excellent DoF calculator at PhotoPills, we can get the minimum depth of field achievable for each lens/body combo at its fastest aperture, shooting a subject at a distance of 2 meters:

 Full Frame
Zeiss Batis 85mm f/1.8
Fujinon XF 56mm f/1.2 R
Micro Four Thirds
M.Zuiko Digital ED 45mm f/1.2
DoF near limit197.21 cm197.09 cm196.61 cm
DoF far limit202.87 cm202.99 cm203.5 cm
Depth of field5.67 cm5.9 cm6.89 cm
DoF in front2.79 cm (49.29%)2.91 cm (49.26%)3.39 cm (49.14%)
DoF behind2.87 cm (50.71%)2.99 cm (50.74%)3.5 cm (50.86%)

Here is the visual breakdown:

Field of view of 3 systems at 2 meters between camera and subject

As you can see, there is almost no DoF difference between the full-frame and APS-C system, and the Micro Four Thirds system ends up with a slightly wider depth of field. The Fujifilm APS-C system ends up beating MFT for narrow depth of field in a smaller overall form factor.

Given equivalent depth of field requirements, the physical size of bodies with lenses attached ends up being roughly the same. Smaller sensors need to compromise for intrinsically higher depth of field properties with bigger and faster glass.

I am currently shooting a Nikon Z6 and I’m quite happy with the combination of body and lens size for a full-frame package.  I find that the Nikkor 28-70mm f/4 kit lens provides a suitably narrow depth of field for most situations, while keeping the overall size and weight down.  Check out our complete Nikon Z mount lens list here.

Small sensor superiority (sometimes)

There are cases where small sensors, such as Micro Four Thirds and even smaller 1″ sensors have a definite advantage:

  • Macro photography, where maximizing depth of field is desirable to reduce the need for focus stacking.
  • Small, light cameras for travel and street photography, where narrow depth of field is not wanted and getting most of the picture in focus is the goal.
  • Situations where extreme telephoto reach is wanted in a small, light package (birding, deep-sky astrophotography, all-in-one superzoom systems, etc.)

What’s your end game system?

Do you need extremely narrow depth of field portraits, and crazy telephoto reach? Are you willing to pay for it? Here’s where the cost/value proposition of full frame starts to break down in a big way.

Canon 600mm adapted to Sony A7III body; equivalent Olympus 300mm

The 600mm f/4 Canon lens above costs north of $11,000 and weighs in at about 8.6 pounds. The equivalent Olympus 300mm f/4 lens costs around $2,500 and weighs just over 3 pounds. In an extreme case like this, the size advantage of the Micro Four Thirds system starts to appear.

Keep in mind that an f/4 aperture on MFT is equivalent to f/8 on full frame, so if you need the most available light to hit your sensor at this range, MFT may not be the right choice. But for birding and other brightly-lit daytime activities, the smaller sensor should do just fine.

Note: I would like to correct the above point based on the comments. A 300mm f/4 Micro Four Thirds lens is equivalent to a 600mm f/8 full-frame lens in terms of total light transmission capabilities. However, smaller format lenses such as Micro Four Thirds have the exact same light gathering abilities as larger format lenses at the same f-stop. For their their native sensor sizes, the intensity of light will be the same.

Optimizing for your needs

Is narrow depth of field your top priority? Cost considerations aside, a full-frame system will likely work best for you. Do you want maximum telephoto reach—or in the case of macro photography, increased depth of field? Micro Four-Thirds is probably your best bet.

For general all-around shooting at a reasonable price, many people find that APS-C sensors offer the best of both worlds.

Which sensor size do you prefer most? Please leave a comment below.

Featured photo by Randy Fath on Unsplash

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  1. Nice write up, but I think you made a mistake. F4 is F4, and the exposure of the sensor will be the same for both those lenses. While there is technically more light coming through the 600mm F4, the sensor is bigger so the light is spread out.

    This is the other advantage of small sensors. You can get the same exposure in lower light without a shallow DOF.

    • Thanks Doug, you’re right! I conflated total light gathering ability with the intensity relative to sensor size. I have made a correction above.

      • I think the best way to describe this MFT FF F Stop DoF argument is to simply state that the Panasonic MFT 35-100mm f2.8 lens gives you the EXACT DoF of a 35-100mm f2.8 lens. But with a 2x crop you have the FoV of a 70-200mm f2.8 lens. While the exposure remains the same because f2.8 is f2.8, the same FoV on the MFT and FF lenses does not have the same DoF.

        It is always framed as if it’s the lenses fault.

  2. Hi Doug.
    Thanks for the article. Just double checking: So, as a rule of thumb: Is the depth of field on a Micro four thirds lens of ie. f/2.0 the same as the depth of field on a Full Frame f/4.0 lens?

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