The Sigma 105 mm f/1.4 Art comes in Canon EF, Nikon F, Sigma and Sony E mount version. In its own house, the 105mm Art has competition from the (cheaper and lighter) 85mm f/1.4 Art and the 135mm f/1.8 Art, both of which we have reviewed before, apart from the difference in focus length, which is often a personal preference of portrait photographers. Although I am not so bothered by it, many portrait photographers find that 85 mm just a bit too short, making the nose too long on a headshot. At 135mm, you stand a bit further away from your subject. In my eyes, the biggest difference in the character of the 105mm f/1.4 Art is at full aperture. Such shots offer you a chance to distinguish yourself from other portrait photographers thanks to the Sigma 105 mm f/1.4 Art.    

Can’t decide? Sigma 85 mm f/1.4 Art, 105 mm f/1.4 Art or 135mm f/1.8 Art?

Although the Sigma 105mm f/1.4 Art is not designed for bird photography at all, Birds in Flight (BIF) shots are a good test for the continuous AF speed. If you manage to get close enough, the Sigma 105 mm f/1.4 Art (with Sigma MC11 adapter) + Sony A7R III will not let you down. Even with very little depth of field, it is possible to catch a bird in flight. 

BUILD AND autofocus

There is 1 switch on the lens, with which you choose between manual or automatic focus. On the top of the lens, there is a small window on which you can read the distance at which you have focused. The relatively large lens hood (made of high-quality carbon fiber to save weight) means, just as with professional bright telephoto lenses, that the lens looks considerably longer than it is. As with the telephoto lens giants, the Sigma 105mm f/1.4 Art has with a tripod collar, which – if you don’t have a Manfrotto – can be attached to your tripod without an extra tripod foot. For transport, you turn the lens hood around, but then the wide focusing ring (with a stroke of more than 100 degrees) is completely covered, so that you can no longer manually overrule the AF or focus manually. In comparison with the Nikkor AF-S 105 mm f/1.4E ED, the only lens with similar features currently available for sale, the Sigma is bigger, heavier and considerably less expensive.
The metal mount is fitted with a rubber ring, so that no dust or splash water can penetrate there. Also at the switch and in a few other places, this lens is extra well sealed against dust and splash water. The rear lens element is used to focus and shifts in position. This lens, on a Sony A7R mk III with the Sigma MC11, focused from infinity to 1.5 meters in 711ms. It is possible that time will be a bit shorter if you use this lens without an adapter on an SLR camera. 

WITH OR WITHOUT LENS CORRECTIONS?

Lens manufacturers design lenses with which distortion, color separation and vignetting are not optimally corrected. They assume that lens errors will later be corrected automatically in the camera (for jpg files) or in Lightroom or Photoshop (for RAW files). The advantage of this choice for the manufacturer and consumer is that you can achieve high image quality at relatively low costs, because you do not have to use expensive types of glass to prevent all lens errors. But there are also lenses, usually the more expensive ones, where a manufacturer has gone to extremes to prevent lens errors in the lens design.
CameraStuffReview shows tables and graphs of Imatest results with lens corrections (“in-camera jpg”) and without lens corrections (“RAW” outside of Photoshop or Lightroom). This way, you can use the scores that best match your workflow. 

IMAGE QUALITY

As soon as you examine practice shots made with the Sigma 105mm f/1.4 Art, you understand why Sigma decided to release this lens in addition to the Sigma 85 mm f/1.4 Art and the Sigma 135 mm f/1.8 Art. More than with both other bright Art telephoto lenses, a photographer distinguishes themselves from other photographers thanks to an extremely beautiful background blur/bokeh. Other strengths include the high resolution across the entire image at full aperture, 

Distortion (-0.09%), and lateral chromatic aberration that is actually absent. Color bokeh (longitudinal aberrations) is remarkably little visible even at full aperture. For a bright lens, which is usually plagued by color bokeh at full aperture, this is a remarkably good result. Without lens corrections, the vignetting was -1.3 stops at full aperture. Thanks to automatic corrections in-camera or in Lightroom or Photoshop, only half a stop remained. These are very good achievements for a lens test on a full-frame sensor, where we regularly encounter 2 stops of vignetting and that even at smaller apertures than f/1.4.

ConclusiON: REVIEW Sigma 105mm f/1.4 Art + Sigma MC11 @ Sony A7R III