Sony’s FE 12-24mm f4.0 G is an ultra-wide angle zoom lens for its E mount mirrorless cameras, and corrected for use on full-frame bodies. It delivers wide to ultra-wide coverage that’s ideal for dramatic urban and natural landscapes and has the distinctive advantage of zooming-out to 12mm which gives an 8 degree wider view over lenses that ‘only’ start at 14mm. It also exploits the short sensor to lens mount distance of mirrorless to achieve a smaller and lighter build than rivals for DSLRs.
The FE 12-24mm f4.0 G was announced in 2017 and is currently listed at 1550 EUR / 1670 USD / 1400 GBP. In 2020 Sony also introduced the FE 12-24mm f2.8 GM at roughly double the price and Sigma also now has its own 14-24mm f2.8 DG DN Art at a price slightly below the FE 12-24mm f4.0 G. So there’re now enough choices in native E-mount to pick an ultra-wide angle zoom lens from.
Facts from the catalog
Let’s compare the Sony FE 12-24mm f4.0 G (“Sony f4.0 G” for short) to the Sigma 14-24mm f2.8 DG DN Art (“Sigma DN”) and Sony FE 12-24mm f2.8 GM (“Sony f2.8 GM”). As usual I’ve rated the features with a [+] (or [++]), when it’s better than average or even state of the art, a  if it’s standard or just average, and [-] if there’s a disadvantage.
Size (diameter x length): All three lenses have a built-in lens hood and don’t change their length when zooming – although the front element of the lenses moves. The Sony f4.0 G is a pretty compact 87 x 117mm (3.4 x 4.6in.). At 86 x 132mm the Sigma DN is longer but the Sony f2.8 GM at 97 x 137mm is biggest lens of the three. [+]
Weight: At 563g (19.9 oz.) the Sony f4.0 G is much lighter than the Sigma DN at 797g or the Sony f2.8 GM at 847g. This is certainly due to it having a less bright f4.0 focal ratio. [+]
Optics: The Sony FE 12-24mm f4.0 G has 17 elements in 13 groups including 4 special dispersion elements and 4 aspherical elements. This is similar to the other lenses in this comparison. To reduce reflections causing flare, glare and ghosting the Sony f4.0 G employs Nano-coating. [+]
Closest focus distance is 0.28m (0.91ft.) at 24mm focal length with a magnification of 1:7.0 which is similar to the Sony f2.8 GM. This results in a working distance of only 15cm. The Sigma DN achieve 1:5.1 at 23cm focus distance. A magnification of 1:10 is achieved at around 0.35m focus distance with all three lenses. 
Filter-thread: None of the lenses in this comparison offer a filter-thread – their bulbous front elements prevent that. So you need to get some non-standard mounting system and a new set of filters. The Sigma DN and Sony f2.8 GM at least allow the use of gel filters in a rear filter holder. Keep in mind though that gels cannot be rotated which precludes the use of polarizers. [-]
Image stabilization: All three lenses in this comparison have no optical image stabilization. But the Sony A7 camera bodies provide built-in sensor-shift stabilization. 
Auto focus: Yes with built-in AF drive. Manual-focus override is by simply turning the dedicated focus ring at the front of the lens. It has a mildly variable gearing covering the focus range in 90 degrees when turned fast and about 200 degrees when turned slowly. This may not be ideal for smooth focus pulling in videos but it is easier than on the Sigma DN with much more variable gearing. All three lenses also have an extra button which can be assigned many different functions e.g. AF-lock. [+]
Lens profile: All tree lens come with a lens profile for vignette-, CA- and distortion-compensation which can be controlled from the camera. [+]
Covers full frame/FF or smaller. Same with the other lenses. [+]
Price: The Sony f4.0 G currently goes for 1550 EUR (incl. 19% VAT) / 1670 USD / 1400 GBP, the Sigma DN is 1450 EUR / 1399 USD / 1299 GBP, the Sony f2.8 GM is at 3300 EUR / 3000 USD / 2900 GBP. 
Aperture ring: None of the lenses in this comparison has an aperture ring. 
The lens comes with a padded pouch but no straps. [+]
Sealing: yes, a rubber grommet at the lens-mount plus further special weather-sealing throughout the construction, just like the other two lenses. [+]
The score in the “features-department” is 1[-]/3/8[+]. The Sony FE 12-24mm f4.0 G is relatively small and light for an ultra-wide zoom lens and offers a good feature set. It may not have the bright f2.8 focal ratio but it starts at 12mm focal length giving a visibly wider field-of-view than other lenses starting at 14mm. Another drawback compared to the alternatives here is that it doesn’t provide for the use of rear gel filters: the only way to use filters is to get some non-standard mounting system for front filters.
If you want to cover the range of focal lengths from 14mm to 24mm there are really only two alternatives to the Sony FE 12-24mm f4.0 G available in the native E-mount:
- Sony introduced the FE 12-24mm f2.8 GM in 2020 with a one stop brighter focal ratio. But then the lens is bigger and 50% heavier than the Sony f4.0 G and comes at twice the price.
- Sigma offers the 14-24mm f2.8 DG DN Art from 2020 at a slightly lower price than the Sony f4.0 G. It might ‘only’ start at 14mm focal length giving an 8 degree narrower view on the short end than the Sonys but it still delivers enormous coverage. The Sigma DN is also one stop brighter than the Sony f4.0 G but for that it is longer and 40% heavier too.
Other alternatives cover different focal lengths like the manual focus Laowa 10-18mm f4.5-5.6 which is currently the only full frame zoom lens starting at 10mm focal length with a recti-linear projection. Or you use older DLSR designs via mount adapter.
Here is the angle of view that the Sony FE 12-24mm f4.0 G covers with its 2x zoom compared to the 1.7x coverage of the Sigma 14-24mm f2.8 DG DN Art:
Focus and zoom
Focus accuracy and repeatability is critical to consistently produce sharp shots. Repeatability (the accuracy of focus on the same subject after repeated focus-acquisition) of the Sony FE 12-24mm f4.0 G at 24mm focal length is good (measured 98.7% in Reikan FoCal) with no outliers over a series of 40 shots. There is also no focus variation whether the lens focuses from a closer distance or from infinity. At 24mm focal length the lens focuses in around 0.5 sec from infinity to 0.35m (1:10 magnification), which is faster than the Sigma 14-24mm f2.8 DG DN Art which took 0.7 sec.
The zoom ring turns through 55 degrees and has a 22mm wide rubber surface with a good grip. It needs less force than the Sigma. The focus ring at the front is 15mm wide and moves smoothly.
AF-operation of the Sony f4.0 G is inaudible from the outside or if you record video with the built-in microphone. Same with the Sigma.
As you pull focus, you’ll hardly notice any focus breathing: When I adjusted the focus from infinity to 0.35m on the Sony f4.0 G I measured less than 2% increase in magnification at 24mm focal length and less than 1% at 12mm. This is similar to the Sigma.
The Sony FE 12-24mm f4.0 G zoom lens is parfocal: When I focused the lens at 24mm and zoomed back to 12mm focus stays on the same spot. Same with the Sigma.
Next check out my quality results!