I tested OM 100-400mm II with Imatest software to check its optical quality in the lab along with the 20MP OM-1 II camera body. The zoom scores in the outstanding range for the sensor at 100mm f/5-11 and 200mm f/6.3-11 (around 2,800 lines), and gets excellent marks at 400mm f/6.3-11 (around 2,400 lines). Fine details like the texture of feathers and fur come through even at 400mm, an improvement over the previous Olympus-branded edition.

OM-1 Mark II, 400mm, f/6.3, 1/400-second, ISO 200 (Credit: Jim Fisher)

The aperture can be narrowed further to f/16-22, but you should try to avoid using such small f-stops with Micro Four Thirds lenses as images soften due to optical diffraction, an effect that causes light particles to scatter as they pass through a small aperture.

The 100-400mm doesn’t show any optical distortion that I could spot. Both JPG and Raw format images show properly straight lines on my test chart. Likewise, illumination is relatively consistent from center to edge, so there’s no need to correct for a vignette.

OM-1 Mark II, 100mm, f/5, 1/250-second, ISO 200 (Credit: Jim Fisher)

The lens does a good job against a backlight too, as its relatively small front element is less prone to flare than brighter telezooms. It does a good enough job that you can forgo using the hood if you prefer. I’d recommend using the hood with this lens, though, as it doesn’t add too much length and guards the glass from damage.

OM-1 Mark II, 227mm, f/6, 1/500-second, ISO 200 (Credit: Jim FIsher)

Micro Four Thirds cameras don’t achieve the blurred background look with the seeming ease of a larger full-frame sensor, but it’s not that hard to get soft backgrounds with the 100-400mm II, especially at the longer end of its focal range. The blur isn’t always buttery smooth—I’d describe its character as busy and frenetic in many scenes. It’s a trade-off that comes with sensor size, and one to which system owners are accustomed.

OM-1 Mark II, 400mm, f/6.3, 1/640-second, ISO 500 (Credit: Jim Fisher)