I was recently lucky enough to get my hands on the Irix 15mm F2.4 lens. The Irix was designed by Switzerland-based TH Swiss, though it was manufactured in Korea.
The lens comes in two versions, “Firefly” and “Blackstone”, which have identical optics but slightly different housing. The cheaper version, the Irix 15mm F2.4 Firefly has lens housing made to a high quality standard with solid plastics. The more expensive version of the Irix 15mm F2.4, the Blackstone, has a magnesium and aluminum alloy housing.
Housing and construction
The lens barrel in both versions is excellent and very precisely manufactured. The focus ring is sufficiently large and rotates with exactly the right amount of tension.
The Irix Lens allows the use of 95 mm screw-in filters at the front in the petal-shape lens hood and gelatin filters at the back of the lens.
Both versions of the lens are made to a level of outstanding quality that I did not expect from a lens in this price range.
Optical performance
Let me first say, that despite its very affordable price, which is slightly over US$448 for the Firefly and around US$673 for the Blackstone, the optical quality of both lenses is truly excellent. For the purposes of testing, I used a Nikon D610, which has a 24MP sensor.
Sharpness
Sharpness and contrast are excellent at all aperture settings and are very good even at the edges of the image. For comparison, I used a Nikon 14-24mm f2.8 lens. On my location test photos, we can see that distortion of the lens is very low.
I compared sharpness between Irix and the Nikon 14-24mm lens, at f/2.8, f/8 and f/22. The Nikon lens was set to 14mm.
As we can see from these test photos, the difference between the two lenses is minimal. At an f/22 aperture setting the Irix is even sharper than the Nikon. On all settings, the Irix also has slightly better contrast. Sharpness is excellent at all apertures in the entirety of the images. A small sharpness drop could be seen only in the furthest corners of the image, which is great for both of these wide-angle lenses. Let me note that this is taking into account that the Nikon 14-24mm f2.8 lens is actually one of the sharpest wide-angle lenses (retailing at US$1899).
Optical Distortion
I have to admit that the optical distortion of the Irix lens is extremely well-controlled. For comparison I tested it against the Nikon 14-24mm f2.8 lens.
Vignetting
Vignetting could be seen with the aperture set to f/2.4. When I stepped it down to f/2.8 the vignetting almost entirely disappeared.
Chromatic Aberrations
Checking all my photos and I could not find any trace of chromatic aberration. Here are two example photos with high contrasts and no apparent CA.
Ghosting and Flare
Ghosting and flare are are very well-controlled with either becoming an issue only in extreme lighting conditions. When light is directly in front of the lens, a reddish ring would appear, but sharpness and contrast of photo are not affected.
Summary
I was incredibly surprised at the quality of the Irix and can easily say it is an excellent lens. Both of the “Firefly” and “Blackstone” versions are optically and mechanically sound. Their sharpness is fantastic, with distortion and vignetting very well controlled. There are no problems with chromatic aberration, and ghosting and flare are are kept in check. I really hope that TH-Swiss produce more lenses like this in future. The Irix 15mm f2.4 is produced for Canon EF, Nikon F and Pentax K mount.
Bojan Stepancic is the official photographer for the office of the European Commission in Slovenia. He has worked with several outlets including Euro 26, E-Fotografija and Moj Mikro magazine. His professional clients include SAP, Lenovo, Nikon, Samsung, Finance, DMS, Nivea, and Bosch. You can find out more on his blog. This article was originally posted here.
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