Although offering different focal lengths both these Olympus ‘fast’ telephoto primes are an option for portraiture or low-light photography. The Olympus M.ZUIKO DIGITAL ED 45mm f/1.8 offers a shorter focal length, which is beneficial for shooting portraits in locations where you can’t take another 3 or 4 steps back. It’s also lighter, smaller and cheaper but how does it compare optically?
Well there’s nothing between the Lens Metric Scores for Transmission, Distortion or Vignetting, although the 75mm version does score marginally better for Chromatic Aberration, 2um to 4um. This is down to the 45mm displaying some minor default at f/1.8 but in the real world there’s very little between these two lenses until you look at Sharpness. A Sharpness Lens Metric Score of 9P-Mpix for the Olympus M.ZUIKO DIGITAL ED 45mm f/1.8 isn’t bad but it can’t live up to the 75mm, which is 15% sharper than the 45mm version.
At the maximum aperture of f/1.8 the 75mm has the edge being sharper in all areas of the frame but particularly in the centre, although the 45mm is more homogeneous at this setting. Stop down to f/2.8 and sharpness of the 75mm really excels with good and homogeneous sharpness compared to the 45mm. The pattern continues at all aperture settings with the 75mm always just that little bit sharper and more consistent than its cheaper rival. It’s fair to say the 45mm is much sharper in the centre at f/2.8, compared to its own performance at f/1.8, but it suffers from heavy drop off in the corners at this setting.