Depth of field for birds in flight – good or bad?
If you would rather head straight to a concise summary, the TL;DR is at the foot of the page — or jump directly to the FAQ.
Many camera enthusiasts see the wide depth of field (DoF) inherent to Olympus cameras, as a disadvantage. In my humble opinion, wide DoF is a positive advantage for landscape photography, for street, and above all, for birds in flight. Shallow DoF is mostly of use in portraiture, and there is no problem at all in achieving it with the Olympus system, particularly with the wonderful 75mm lens.
TL;DR
- Olympus has 4× the depth of field of full-frame cameras when matching subject magnification and aperture (same effective f-number).
- For birds in flight, this is an advantage: wider DoF means AF uncertainty tolerance is higher, missing focus is less critical.
- Full-frame 2–3 stop shallower DoF requires tighter AF, faster shutter speeds, and more precision for keepers—opposite of what BIF photographers need.
- If shallow DoF is desired for BIF (e.g., for portraiture of perched raptors), Olympus 75mm f/1.8 delivers f/3.6 effective (shallow for MFT) with 5-stop IBIS.
- Wide DoF is often mischaracterised as weakness; for action and wildlife it is a structural advantage.
Frequently asked questions
Why does subject magnification matter for DoF comparison?
DoF scales inversely with aperture and magnification. To compare systems fairly, you must match both. EM1x at 100mm f/2 produces 2× magnification at 50mm DoF. A9 at 200mm f/4 produces the same magnification and DoF. Comparing EM1x to A9 at 300mm f/4 is unfair—the A9 is at 3× magnification and shallower DoF.
Is wide DoF actually good for birds in flight?
Yes. AF uncertainty in continuous tracking = ±0.5–2mm focus error. With EM1x’s wide DoF, ±2mm error is invisible. With A9’s shallow DoF at equivalent magnification, the same error causes slight softness. Wide DoF tolerates AF jitter; shallow DoF amplifies it.
Can Olympus achieve shallow DoF if needed?
Yes. The 75mm f/1.8 lens on EM1x produces f/3.6 effective aperture at 1.5× magnification (shallow for MFT). Not f/1.8 equivalent full-frame shallow, but 1–2 stops shallower than the standard 100mm f/2 and sufficient for selective focus on perched raptors.
Does IBIS interact with DoF?
Indirectly. IBIS allows slower shutter speeds at lower ISOs; lower ISO improves shadow detail and simplifies post-processing. It does not change DoF itself, but enables shooting at smaller apertures (higher ISO penalty is lower).
Full-frame in crop mode: does it narrow DoF?
No. Crop mode removes pixels (e.g., A9 crop to 18MP); magnification is identical, aperture is unchanged, so DoF does not narrow—but signal-to-noise ratio degrades. Avoid full-frame crop mode entirely for BIF.
