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HandeVision Ibelux 40mm f/0.85 review – Resolution, shading and curvilinear distortion
A close look at our Applied Imaging tests confirms what we found by studying our real-world images. At f/0.85, the centre of the image is noticeably sharper than the corners. Centre sharpness improves as the lens is stopped down to f/5.6, with sharpness at the edges improving beyond f/2 right up to f/8. Users wishing to find the sweet spot between centre and edge sharpness will want to use the lens around f/5.6 and to help remind users that this is the optimum aperture for edge-to-edge image sharpness f/5.6 is coloured green on the barrel.
Using the lens at its maximum aperture introduces corner shading at the edges, with corners appearing approximately 1.2EV darker than the centre of the image. Stopping the lens down to f/1.4 sees an improvement, with corners appearing 0.8EV darker than at the centre. You can use the lens between f/2.8-f/22 safe in the knowledge that vignetting won’t be an issue.
An inspection of our distortion chart reveals the lens exhibits some barrel distortion, whereby the straight lines bow outwards a little towards the edge of the frame. In real-world images, you’ll be hard pushed to notice it unless you go in search of it. To counteract the minor barrel distortion in my test images, I took manual control of the distortion amount slider in Lightroom and set it to a value of +5.