The following chart presents a comparison between basic parameters of the tested lens and other full frame f/2.8 fixed-focal instruments with similar focal ranges. It is clear that, when compared to reflex camera rivals, the tested Sigma is physically lighter and smaller. It also features as many as 11 aperture blades – an interesting thing as, usually, you don't find so many blades in ultra wide-angle lenses.
In the photo below the Sigma A 14-24 mm f/2.8 DG DN is positioned next to full frame Sigma A 35 mm f/1.4 DG HSM designed for reflex cameras.
The tested lens starts with a metal mount surrounding contacts and a black, plastic part of the barrel you can put filters in. The filters' holder is a tad bigger than the 28×22 mm frame you find before a rear element.
The rear element itself is 22 mm in diameter and it doesn't move. It is positioned at its shallowest at 14 mm and it hides almost 2 cm deep when you set the focal length at 24 mm. In that position you can glimpse a perfectly blackened, matted, and ribbed interior of the tube, without any slits or electronic parts.
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The first part of the proper barrel consists of a sleek, black, metal ring which quickly and smoothly increases its diameter. On the ring you can find: a white dot, making the alignment with a camera easier, „019” marking the model year of the instrument, an inscription „MADE IN JAPAN”, and the focusing mechanism working range - „0.28M/0.92FEET–∞”.
The next part is a zoom ring, 22 mm wide, mostly covered by rubber ribbing on which you can find focal length markings at 14, 16, 18, 20, 22, and 24 mm. The ring moves smoothly and is well damped.
Further on you see an immobile part covered by plastic with the company's logo, the name and parameters of the lens, its serial number, fine ribbing, „A” symbol, meaning the lens was qualified as an A series device, and two controls. The first of them – the AF/MF FOCUS- is used for choosing the focusing mechanism mode and the second one – the AFL button – allows you to lock and recall a specific autofocus position. Other functions can be attributed to it as well.
The next part of the lens's body is a manual focus ring, 24 mm wide, mostly covered by ribbing. Next to it you don't find any distance or depth of field scale. The ring is a focus-by-wire construction and it turns very smoothly but with proper resistance. Its range depends on the speed of your turning. If you turn the ring quickly you can cover the whole range with an angle of 180 degrees, if you turn it slower you might even need 550 degrees. Both or these are rather high values, allowing you precise manual settings.
The lens's body ends with a petal-type hood made of plastics which surrounds a noticeably convex front element, 63 mm in diameter. The front element changes its position and is the most extended at the 14 mm focal length.
The lens's casing is supposed to be dust- and splash proof with water- and oil-repellent coating on the front element which also ensure more comfort in taking photos in different conditions. There is also a build-in rear filter holder with a fall prevention lock for attaching sheet-type gel filters.
When it comes to optical construction you deal here with 18 elements positioned in 13 groups and the number of special ones among them is really impressive. You get one low dispersion FLD element made of glass with properties similar to fluorite, four low dispersion SLD glass elements, two aspherical elements and one element which, at the same time, is aspherical and made of SLD glass. Additionally the rounded aperture of the lens features as many as 11 diaphragm blades and it can be closed down to a value of f/22 at the maximum.
It's worth mentioning that usual antireflection coatings this time are paired with the new NPC technology (Nano Porous Coating) which contains porous nano-particles of silicon in the coating material.
