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

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 CameraSize.com 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
APS-C
Fujinon XF 56mm f/1.2 R
Micro Four Thirds
M.Zuiko Digital ED 45mm f/1.2
DoF near limit 197.21 cm 197.09 cm 196.61 cm
DoF far limit 202.87 cm 202.99 cm 203.5 cm
Depth of field 5.67 cm 5.9 cm 6.89 cm
DoF in front 2.79 cm (49.29%) 2.91 cm (49.26%) 3.39 cm (49.14%)
DoF behind 2.87 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.

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 EF 600mm f/4L IS II USM lens adapted to Sony α7 III body; focal-length equivalent Olympus M.Zuiko Digital ED 300mm f/4 IS PRO lens

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.

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 header photo by rawpixel.com on Unsplash.

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