Depth of Field on Micro Four Thirds
Depth of field is the band of your scene that looks acceptably sharp. It is the single most misunderstood part of moving to or from Micro Four Thirds, because the smaller sensor changes it in a way that is easy to state wrong. This guide explains what actually happens, why, and how to use it, including hyperfocal distance for landscapes.
What depth of field actually is
Depth of field is the range of distances in your scene that appears acceptably sharp. A shallow depth of field means only a thin slice is in focus, with the background and foreground blurred, which is what gives portraits their subject separation. A deep depth of field keeps everything from near to far sharp, which is what you want for landscapes. Three things control it: the aperture, the focal length, and how far you are from the subject.
- Aperture: a wider aperture (smaller f-number, like f/1.8) gives a shallower depth of field. Stopping down (f/8, f/11) deepens it.
- Focal length: longer lenses render a shallower depth of field at the same aperture and framing.
- Distance: the closer you focus, the shallower the depth of field. This is why macro depth of field is razor thin.
The crop factor and depth of field, stated correctly
This is where most explanations go wrong, so here is the careful version. At the same aperture and the same actual focal length, a Micro Four Thirds sensor and a full-frame sensor capture different framing, so that is not a fair comparison. The fair question is: for the same photo, meaning the same field of view and the same subject distance, how does depth of field compare?
Answer: Micro Four Thirds gives you more depth of field than full frame at the same f-number. To match the framing of a 50mm lens on full frame you use a 25mm lens on M43. That shorter lens, at the same f-number, has a deeper depth of field. The size of the effect is the crop factor, which is 2x for M43. So M43 at f/2.8 has roughly the same depth of field as full frame at f/5.6. Put another way, M43 behaves as if it has about two stops more depth of field than full frame for the same shot.
This is the same two-stop relationship covered in the M43 to Full Frame Converter. It is the reason people say M43 struggles to blur backgrounds as much as full frame, and it is true. But the same property is a genuine advantage for landscape, macro, and any work where you want depth, because you can use a wider aperture, let in more light, and still keep the scene sharp.
What this means in practice
If you want maximum background blur on M43, use a fast prime and get close. The Olympus 45mm f/1.8 (90mm equivalent) and the Panasonic Leica Nocticron 42.5mm f/1.2 are the classic portrait choices, with the f/1.2 Nocticron giving the strongest separation in the system. For even shallower rendering, the Voigtlander Nokton 25mm f/0.95 manual primes go further than any autofocus lens.
If you want everything sharp, the extra depth of field works for you. A landscape that needs f/11 on full frame to hold front-to-back sharpness only needs about f/5.6 on M43 for the same result. That wider aperture lets in two stops more light, so you can keep ISO lower or shutter speed faster. There is a catch, which is diffraction.
Because M43 packs its pixels into a smaller sensor, diffraction softens the image at wider apertures than it would on full frame. On a 20MP M43 body, sharpness starts to drop past roughly f/8, so stopping down to f/16 to chase depth of field is usually counterproductive. The Diffraction Limit Finder shows the exact threshold for your camera. The practical takeaway is that the deeper native depth of field is helpful precisely because you rarely need to stop down as far on M43.
Calculating depth of field for a shot
For a specific scene, the Depth of Field Calculator gives the near limit, far limit, and total depth of field for any focal length, aperture, and focus distance. It is set up for the M43 circle of confusion of 0.015mm, the standard value used to define acceptable sharpness on this sensor. Enter your lens and aperture and it tells you exactly how much of the scene will be sharp.
Hyperfocal distance for landscapes
Hyperfocal distance is a specific focus distance that gives you the maximum possible depth of field for a given focal length and aperture. When you focus at the hyperfocal distance, everything from half that distance all the way to infinity is acceptably sharp. It is the technique landscape photographers use to keep both a near foreground and distant mountains sharp in the same frame.
The common mistake is focusing on infinity, which wastes all the depth of field that would have fallen behind infinity and leaves the foreground soft. Focusing at the hyperfocal distance instead pulls the near limit of sharpness much closer while still holding infinity. On M43, the hyperfocal distance is closer than on full frame at the same equivalent framing, which again is the deeper depth of field working in your favour for landscapes.
The Hyperfocal Distance Calculator gives the exact focus distance for any M43 focal length and aperture, with a reference table for common combinations. In the field, focus a third of the way into the scene as a rough rule, or focus precisely at the hyperfocal distance the calculator gives for a critical shot.
Matching settings across systems
If you are coming from another format and want to reproduce the exact look you are used to, the Equivalent Settings Calculator translates focal length, aperture, ISO, and shutter speed from one sensor size to another so that field of view, depth of field, and exposure all match at once. It is the quickest way to answer questions like what M43 lens and aperture gives the same photo as a 35mm f/2 on full frame.