![]() The lens also does very well to minimize axial chromatic aberration, which causes fringing around high-contrast transitions in front of and behind the plane of focus at wide apertures. There’s only negligible lateral chromatic aberration, even at the extreme edges and corners of the frame. Even so, it’s not overly bad and these aberrations virtually disappear if you narrow the aperture by a single f/stop. The only niggle for astrophotography and nighttime cityscapes with lots of pinprick lights is that, when shooting at f/1.8, coma and astigmatism can be noticeable towards the corners of the image frame, which give stars and lights an irregular shape. It chronically weighs down you camera bag, which is galling if you only intend to use it occasionally at night. ![]() However, the Sigma 14mm f/1.8 is not perfect. Add to that some fine detail, excellent contrasty colours, and a near-silent auto-focus, and it’s quite a package. In fact, you can add another win, because its f/1.8 setting also means a shallow depth of field, so when used in daylight it's easy to create shots featuring a clean and seamless bokeh effect. Shorter exposures also means sharper stars with less trail. A shorter exposure and a lower ISO means less noise. Since the shutter is open for less time to capture the same amount of light, it means using a lower ISO. You can frame a shot more easily while out in the field, but the real benefit is a clean image. Using the Sigma Art 14mm, the Milky Way is right there in the LCD on the back of the camera, especially if the exposure time is 20 seconds or more. For example, a 25-second shot on a f/2.8 lens gets the Milky Way looking bright, but only after it's been teased-out on Photoshop. Put simply, collecting more light gives you a lot more options. Used on the Milky Way at f/1.8 for 10-25 seconds at ISO 3200-4000, the results on a full-frame Canon EOS 6D were impressive. Instead of trying to maximise the amount of light coming into a f/2.8 lens by braving higher and higher ISO settings (and thus battling noise in post-editing), having access to the f/1.8 chops of the Sigma 14mm means ISO can be left on a conservative setting. Use the Sigma 14mm f/1.8 for astrophotography and concerns about which ISO setting to use pretty much become a thing of the past. ![]() ![]() Barrel distortion can be noticeable when uncorrected but it’s of a fairly small amount and of a much lower order than in many more recent lenses designed for mirrorless cameras, which rely heavily on in-camera correction. Image quality is equally impressive in terms color fringing, which is negligible across the whole frame, at all aperture settings. Impressively for such a fast, wide-angle lens, they remain that way even when you’re shooting wide-open at f/1.8. Levels of sharpness are excellent, from the center of the frame right out to the extreme edges and corners. Unlike lenses with stepping motor-based autofocus that have electronically coupled focus rings, you don’t need the host camera’s exposure system to be active to apply manual focusing, as no electronic power is required. When overriding autofocus or focusing manually, the mechanically coupled focus ring works with smooth precision. Autofocus proved fast and reliably accurate in our tests, while the ring-type ultrasonic autofocus system enables full-time manual override. ![]()
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