Coma is absent in the center of the frame, gets worse toward the edges/corners, and generally appears as a comet-like or triangular tail of light which can be oriented either away from the center of the frame (external coma) or toward the center of the frame (internal coma).

I can’t explain the blur problems at f/4. As I mentioned, I always re-focus between every shot, and the chances against having encountered vibrations every time at f/4 are too high to accept as an explanation, especially considering the shutter speed was around 1/1000th of a second, so vibrations shouldn’t have been a factor anyway. The Sigma 24mm f1.4 DG HSM Art Lens is another wonderful addition to the SIGMA Art line and is perfect for nightscapes, starry skies and cityscapes. It offers the highest optical performance in its class in addition to minimising coma flare, chromatic aberration, distortion and vignetting. The SIGMA 24mm F1.4 DG DN | Art is equipped with both a front filter thread and a rear filter holder, as well as a new MFL switch that disables the focusing ring to prevent accidental changes that will be especially helpful when photographing the stars at night. The dust- and splash-resistant structure of the lens itself and the water- and oil-repellent coating of the front element will keep the lens safe and functioning even during shoots in harsher environments. Landscape and architecture photography are two photographic disciplines that have frequent scenarios requiring sharp corners. With the hood removed, about 3.7" (94mm) of working distance is available, still making shadows a concern for lighting.The Sigma 24mm F1.4 DG DN Art Lens design includes two FLD elements and one SLD element to correct for chromatic aberrations and ensure overall high image quality. Internal autofocus is driven via a stepping motor and, as with the 20mm F1.4 lens, Sigma says this lens is compatible with Sony’s AF Assist functions. On supported L-mount cameras, the lens will work in both linear and non-linear focus ring response modes. In regards to the Sony E-mount version of this lens, Sigma develops, manufactures, and sells lenses based on the specifications of E-mount, disclosed by Sony Corporation under license agreement. Like other models in the I series, Sigma supplies not one but two lens caps, so as well as the usual spring-loaded plastic cap, there’s an additional metal disc which attaches magnetically, with a satisfying snap and the magnet feels strong enough to keep it in place too. With the hood mounted though, this second cap is a little awkward to fit or remove, so it’s arguably a bit of a novelty, but I like that Sigma’s trying something different here.

Price: The Sigma costs around 750 EUR (incl. 19% VAT) which is not cheap but a fair price for the ambition Sigma has for this lens. The AF-S 24/1.4G ED Nikkor for example costs more than double that at around 1700 EUR. But the manual focus Samyang is even cheaper than the Sigma at around 550 EUR. [+] This one shows gradually decreasing image quality into the corners, with peripheral shading and lateral CA adding to the decline. Capture breathtaking images with ease in any lighting condition with the SIGMA 24mm F1.4 DG DN | Art lens, featuring wide viewing angle and astrophotography-level optical performance

Build Quality and Handling

The lens mount is impressively made using brass, and as mentioned also includes a rear gelatin filter slot.

The Sigma 24mm f/1.4 DG HSM | ART was, I believe, the only ART series lens that I missed reviewing when it was initially released. In the past few months Sigma has been releasing new versions of its ART series in Sony FE (full frame E-mount), so I thought I thought I would kill two birds with one stone by both reviewing a lens that I had missed and also expanding the sample size of ART series on FE lenses beyond the 50mm f/1.4 ART Review on FE I did a few months ago. The 24mm focal length is obviously a very popular one, and combining a great focal length with a great maximum aperture of f/1.4 really expands the creative opportunities. Sigma had this Sony FE market at this focal length and aperture value to itself for a few short months, but Sony has already thrown a bit of a monkey wrench into the 24 ART’s market by announcing the new 24mm f/1.4 G Master lens. That comparison will be interesting, for the new GM lenses costs 60% more but the 24 ART weighs 73% more. If my past experience bears true, the optical performance will be competitive between the two lenses, with some give and take from them both. I’ll probably revisit this when I review the 24 GM lens in the future. With the right lens profile and software, lateral CA is often easily correctable (often in the camera) by radially shifting the colors to coincide.The spherical aberration color halo shows little size change as the lens is defocused, and stopping down one to two stops generally removes this aberration. By incorporating "F" Low Dispersion (FLD) glass as well as Special Low Dispersion (SLD) glass elements, the lens is able to minimise chromatic aberration of magnification that is mostly visible around the edge of the image. In addition to this correction of axial chromatic aberration is a possibility thanks to the aforementioned power layout. This lens achieves high image quality as well as sharp and high contrast image rendering without any colour blur. Minimised Distortion Ultimately, both lenses are optically excellent, especially in the center of the frame, but the Sony maintains an advantage in resolution and sharpness away from the center of the image at f/1.4 and f/2, and in the corners (probably) until f/5.6. An advantage of this hood shape is easier alignment (simply learn the small petal to the top installation orientation), though a round-shaped hood better enables the lens to stand on its hood.