The 40-150mm f/2.8 PRO indicates its position as a professional-grade optic right in the name of the lens, and it lives up to this billing in its resolution abilities. The lens seems to be optimized for the portrait range distances, and in this range, the lens is incredibly sharp from f/2.8 throughout the entire focal range. Center sharpness is brilliant and even edge and corner sharpness is very good at f/2.8, and improves to excellent when stopped down just a smidge.
While the lens is optimized for closer focusing distances, it’s no slouch further out either, though it falls just short of the very best lenses near infinity. Central sharpness is still absolutely brilliant throughout the focal range, even wide open, though the edges at f/2.8 do tend to suffer a bit. They are good, but not exceptional. Stopping down to f/5.6 brings the edges and corners to very good territory here, while the center remains stunningly sharp. While there are sharper lenses for landscape use, the level of resolution should be enough for all but the most critical pixel peepers when focused near infinity.
Short telephoto zoom lenses tend to be a go-to sort of lens for portrait photography and event shooting, and as such, the out of focus rendering is of concern to most photographers. The 40-150mm f/2.8 is a bit of a mixed bag in this regard. Overall, there’s nothing too objectionable about the bokeh created by the lens, but it also doesn’t generate that smooth bokeh that many other f/2.8 telephoto zooms can create.
Specular highlights are generally evenly illuminated, and the lens avoids bright-ring highlights for the most part. However, out of focus highlights do show the tell-tale onion-ring pattern that is indicative of aspherical elements in the lens design. In many situations, the overall rendering of the lens is quite pleasing, but once you start focusing a bit further out, images can get just a touch nervous in the background depending on the scene. The image below is just such a case.
Contrast, Color and Chromatic Aberration
The Olympus 40-150mm f/2.8 produces images with high levels of contrast throughout the focal range and the aperture range. The only mild dip in contrast seems to come wide open at focus distances around 15-40 feet away. However, this is very minor and can be easily compensated for in post-production. Color is rich and natural, with good color response and a neutral rendering.
The lens controls chromatic aberration very well, both laterally and longitudinally, so there’s nothing much to worry about here, except perhaps at the wide end, where a bit of lateral CA can creep into the corners. At the mid and long ends of the zoom, though, it’s extremely minimal.
Distortion, Flare and Vignetting
The 40-150mm f/2.8 is quite benign when it comes to distortion, with nothing field relevant in the images. Vignetting is also generally well controlled, with some minor vignetting visible at f/2.8, but gone by f/4. However, if there’s one weakness with the 40-150mm, it’s flare.
This lens flares horribly if the sun (or a reflection of the sun) is either in the frame or just out of the frame. Large purple swaths of flare obscure the image and contrast is massively reduced. Even when the sun is just barely out of frame, a bright purple flare will be quite apparent at the edge of the image frame. The lesson? Don’t shoot this lens into the sun, unless you want to compose with flare in mind. Check out the image above to see how bad it can get.