Sony FE 14mm F1.8 GM (SEL-14F18GM
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Sony FE 14mm F1.8 GM (SEL-14F18GM)

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The Sony FE 14 mm F1.8 GM (SEL-14F18GM) is the most wide-angled fixed focal length to date for the mirrorless full-frame system cameras from Sony. Despite the large angle of view of 114 degrees, it is comparatively compact, especially when compared to corresponding DSLR lenses. However, such ultra-wide angles are optically very demanding to design, especially if they are to have a high edge resolution and only minimal optical errors. Our test on the 50 megapixel Sony Alpha 1 shows whether the Sony FE 14 mm F1.8 GM did well.   (Benjamin Kirchheim)

With a flange focal length of 18 millimeters, not only theoretically compact wide-angle fixed focal lengths can be built for the Sony E bayonet, as Sony already demonstrated at Photokina 2018 with the presentation of the FE 24 mm F1.4 GM, which also very much in our test good performance (see related links). The 24 mm and the new Sony FE 14 mm F1.8 GM (SEL-14F18GM) have even more in common: like the 24 mm, the 14 mm should also be particularly suitable for astrophotography thanks to special corrections.

processing

At first it is hard to believe that the FE 14 mm F1.8 GM, which is only 8.3 centimeters in diameter and almost ten centimeters in length, also offers a light intensity of F1.8. The low weight of 460 grams is also impressive. No other 14mm F1.8 is this slim and light.

Sony also saves weight on the housing, which is only made of metal to a small extent (aperture ring and bayonet), but is largely made of plastic. But that doesn’t detract from the high-quality feeling. The robustness is underlined by the dust and splash protection, whereby Sony emphasizes as always that no guarantee is given for the protection.

As with the FE 12-24 mm F2.8 GM (SEL-1224GM), the lens hood is an integral part of the lens construction. There is no filter thread and a special but simple hooded construction is used as the front cover. The large front lens bulges strongly forward, but fortunately does not protrude beyond the four wings of the tulip-shaped lens hood, so that a certain mechanical protection is guaranteed. Thanks to the fluorine coating, the dirt-repellent front lens is easy to clean.

Instead of a filter thread, the FE 14 mm F1.8 GM offers a film filter holder on the rear of the lens on the bayonet. This is also known from the FE 12-24 mm F2.8 GM. If you want, you can cut your own foil using the template provided.

Equipment and operation

The Sony FE 14 mm F1.8 GM has an astonishingly large number of controls for a fixed focal length: two setting rings, two slide switches and a button can be found on the housing. At the very back is the 1.3 centimeter wide bezel ring, which is made of metal. Half of the width is grooved for the necessary grip, on the other half the entire f-stops from F1.8 to F16 are labeled and engraved with a 1/3 f-stop scale and laid out in high-contrast white paint. The aperture ring engages fully and also has an automatic position with a further adjustment range to F16 and clear engagement. It is not that easy to accidentally leave the automatic position.

Automatic position is not quite the right word for it anyway, because it only has an effect in manual or automatic timing mode. In automatic iris, programmed or fully automatic modes, the camera takes control of the actual aperture setting regardless of the aperture ring setting. If the aperture ring is set to automatic in manual or aperture priority mode, the aperture can be set using a function wheel on the camera, i.e. it is not set automatically.

Videographers should be pleased with the slide switch labeled “Click” on the lower right: If you switch it from “On” to “Off”, the aperture ring runs continuously and without detents. Even if the camera does not display any finer gradations than 1/3 f-stop on the screen or in the viewfinder, the aperture works completely steplessly.

The manual focus ring, which is two centimeters wide, can be found far to the front of the lens. It is made of plastic and is provided with a 1.5 centimeter wide, non-slip ribbed rubber. It works completely steplessly, is very (perhaps a little too much) smooth and electronically transmits setting commands to the autofocus motor. The focus is adjusted by two XD linear motors that push the focus group directly forwards or backwards without turning. Linear is also the keyword for manual focusing, because the focus ring works linearly, which should be particularly useful for videographers. This means that the angle of rotation of the focus ring alone determines the adjustment path, not the speed of rotation.

The focus motors work almost silently, mechanical noises can only be heard if you hold your ear to the lens while focusing. The autofocus works accordingly quickly, quietly and precisely. However, manual focusing is also completely problem-free with this combination, not least thanks to the camera’s setting aids such as focus peaking or the focus magnifier.

The slide switch at the bottom left of the lens is used to switch between auto and manual focus. Directly above it is a button that can be freely assigned a function via the camera menu. By default, the key activates the focus stop function. According to the technical data, the closest focusing distance is 25 centimeters, but we were able to focus from 22.5 centimeters away from the image sensor. The distance between the front of the lens and the subject is just over 10.5 centimeters.

Due to the large diagonal angle of view of 114 degrees, the minimum image field of 32 by 21.3 centimeters is still quite large, resulting in a maximum reproduction ratio of 1: 8.9. This is not much, but a bit better than the 1:10 promised by Sony.

  • With a length of just under ten and a diameter of 8.3 centimeters, the Sony FE 14mm F1.8 GM (SEL-14F18GM) is much more compact than other 14mm lenses for the 35mm format. At 460 grams it is also quite light. [Photo: MediaNord]

picture quality

At least 14 lenses in eleven groups are used in the Sony FE 14 mm F1.8 GM. A Super ED glass, two ED glasses, an aspherical lens and even two XA (eXtreme Aspherical) lenses should not only ensure high resolution right up to the edge of the image, but also minimize optical errors. As with the FE 24 mm F1.4 GM, this applies in particular to the perhaps not so well-known sagittal chroma. This should especially please astrophotographers, because it means that point-shaped objects at the edge of the image really remain point-shaped. In addition, nine aperture blades are used, which ensure a particularly evenly round opening and thus contribute to the beautiful bokeh of the G-Master lens.

In fact, the lens offers a predominantly excellent image quality in practice. The bokeh is very even and is particularly evident when focusing on very close subjects with the aperture open. Fine details merge very nicely in the blurred area without forming double contours that would bring unrest into the background. It looks just as good in the foreground. However, you have to be careful with highlights in the out-of-focus area. So-called onion rings appear here, and the edge of the blurring discs is slightly lighter. On the other hand, we couldn’t make out any color fringes in the bokeh.

Lenses with aspherical lenses are susceptible to these onion rings, which result from unevenness in the lens surface and especially in the coating. Although this is not supposed to happen with Sony’s Nano AR Compensation II, these rings are clearly visible. The fuzzy discs of highlights look like sliced ​​onions (see example image).

When it comes to backlighting, which is particularly important with such wide-angle lenses, the nano coating, on the other hand, does an excellent job. The contrasts remain high in the photo even in direct backlight with the sun and the lens flare is minimal. If you stop down to F16, you also get a beautiful sun star with 18 rays, which result from the nine aperture blades (see also example image).

In the test laboratory on the 50 megapixel Sony Alpha 1, on the other hand, the picture is rather mixed. First of all, it should be mentioned that our laboratory tests are carried out in JPEG with factory settings. For the Sony FE 14 mm F1.8 GM, this means that color fringing and edge darkening are corrected, but the distortion is not. All corrections can be switched on and off with the 14 mm.

The edge darkening is not too high with a maximum of 0.9 f-stops at F1.8, especially since it increases very evenly and is therefore hardly noticeable. When stopping down to F2 and F2.8, it drops by 0.3 EV and then remains at this low level of 0.3 f-stops when stopping down further. When the correction is switched off, the edge darkening is slightly higher, but not dramatic and still hardly disturbing.

Even if we didn’t notice any color fringes visually in the unsharp area, it looks different in the sharpness area. The laboratory test confirms that the Sony FE 14 mm F1.8 GM has low chromatic aberrations on average, but with a maximum of 1.7 to 1.8 pixels they reach the easily visible range.

The distortion is surprisingly low for such an ultra-wide-angle lens, despite the correction being switched off. It is only around 1.5 percent barrel shape and is therefore only visible in the case of very critical motifs. If you activate the distortion correction, the distortion disappears completely. But be careful: the correction has to stretch the pixels, which can cost a bit of resolution.

Speaking of resolution: In the center of the image, with a contrast of 50 percent, it is already high from an open aperture. It reaches almost 85 line pairs per millimeter (lp / mm) and can only be increased minimally to 87 lp / mm by stopping down, which is achieved at F2.8. When stopping down further, the resolution drops again and is below 80 for F8 and F11 and even below 70 lp / mm for F16. It looks pretty bad at the edge of the picture. With an open aperture, only 23 lp / mm are achieved, which corresponds to over 70 percent loss of resolution (see diagram from the laboratory test below). In view of this low value, the loss of resolution should be clearly visible even with a 35mm camera with a resolution of only 24 megapixels.

When stopping down, the edge resolution increases only very slowly, even with F5.6 only 40 lp / mm are achieved at the edge of the image, the relative edge drop is also very high here at 50 percent. Only at F11 does the edge resolution increase significantly to 60 lp / mm, the relative edge drop is only a good 20 percent. So if you want to take landscape photos, you should fade down to F11 if the photos should show a lot of details right up to the edge of the picture. After all, the edge resolution is significantly higher with lower contrasts. At ten percent contrast, up to 113 lp / mm are achieved at the edge and up to 120 lp / mm in the center of the image, which is the resolution limit of the 50 megapixel sensor. The problem with it: For the human eye, such low contrasts are hardly perceived as sharp, which is why we have these data, although they are also measured,

Conclusion

The Sony FE 14 mm F1.8 GM (SEL-14F18GM) is an impressively compact ultra-wide-angle lens with a large diagonal angle of view of 114 degrees, but this is subject to major compromises, especially when it comes to image quality, which is why you should carefully consider whether you really want to pay almost 1,600 euros for it. If a little less light intensity or less wide angle is required, there are much better alternatives, such as the (albeit twice as expensive) Zoom FE 12-24 mm F2.8 GM and the (much cheaper) FE 20 mm F1.8 G, the However, you should stop both of them a bit (but not nearly as much as the 14 mm), or the excellent FE 24 mm F1.4 GM (all test reports can be found in the links below).

After all, the good workmanship, splash protection, compact dimensions, the fast, quiet autofocus, the optionally stepless aperture ring and the good image quality with the exception of the edge resolution and the onion rings in bokeh highlights remain on the credit side of the Sony FE 14 mm F1.8 GM . In the backlight, the contrasts remain high and the bokeh is nice and soft. The optical errors are small and the resolution in the centre of the image is already high from the aperture open. However, you only get a high edge resolution with F11; if you fade in further, the resolution edge drop is up to over 70 percent.

Peter High
I've written for the Wall Street Journal, CIO Magazine, CIO Insight, Information Week and several other periodicals. I am also the author of Implementing World Class IT Strategy: How IT Can Drive Organizational Innovation.

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