The announcement of a new APS-C Art lens by Sigma has given me food for thought - Is this lens the 'best thing since sliced bread' or does it just serve to advertise the merits of a compact Full-Frame system (for those interested in accessing performance and weight-saving advantages)?
Some may think that there has NOT been a lot of innovation in the crop sensor (APS-C) market since Sony released its wide-angle prime lenses (E 11mm F1.8 and E 15mm F1.4 G) in June 2022 and the A6700 in July 2023. Sigma, therefore, have to be applauded for making a premium quality F1.8 Art lens (17-40 F1.8 DC Art) available for APS-C photographers. Two of the reviewers I have seen promoting this lens on YouTube say (in the movie title) that this is “the best APS-C lens ever” and that it is “the Holy Grail of APS-C lenses”. So, let’s unpack some of the specifications to see if this lens can live up to the ‘hype’. Note - I have not used this lens (as a Sony Ambassador I will have to purchase this lens in order to review it) but I do own three Sigma lenses (two of which are from their APS-C range). What makes this new Sigma F1.8 aperture lens special (significant), apart from its bright F1.8 aperture, is that it is a premium ‘Art’ series lens and boasts 11 circular aperture blades + internal zoom (compared to the 7 aperture blades and external zoom of the Sigma 18-50 F2.8 DC DN lens).
Although some reviewers are describing this as a compact zoom lens, it is significantly larger and heavier when compared to its extremely popular 18-50 F2.8 DC DN lens (19.8 oz / 560 g vs 10.2 oz / 290 g) and 33% heavier than Sony’s premium quality E 16-55 F2.8 G APS-C lens. Many photographers will be attracted to this new 17-40 lens because of its wide F1.8 aperture for low-light photography and increased figure/ground separation (background bokeh). Shallow depth of field, however, is not just a matter of having a lens with a wider aperture. Distance and Focal Length are also major contributing factors to depth of field, and in this regard the lighter, smaller and cheaper Sigma 18-50 DC DN lens, with its better magnification ratio (close focusing capability) and it longer focal length (50mm compared to 40mm), makes the difference between F1.8 and F2.8 seem not so great when background blur is the priority. In many instances the blur behind the subject will be greater when using the 18-50 at a closer focusing distance. When compared to super-popular Sigma 56mm F1.4 DC DN prime lens there is a significant difference (in favour of the 56mm prime) when you factor in the longer focal length and wider F1.4 aperture. It’s no longer simply the difference of 2/3 stop (F1.4 compared to F1.8).
Although the wide F1.8 aperture is useful at the wide-end of the zoom range, vloggers and landscape photographers would benefit from the wider angle of view offered by the Yongnuo’s 11mm F1.8, Sony’s E11mm F1.8 or E 15mm F1.4 G prime lenses or a Sony E 10-20 F4 Power Zoom. One of the big advantages for APS-C photographers is the lightweight and compact nature of their system when compared to equivalent full-frame photographic systems. As the A6700 camera is not much smaller or lighter than Sony’s current A7C cameras, this advantage must come through careful choice of the available lenses.
If we compare the size and weight of the Sigma 17-40 F1.8 DC Art lens with Sony’s FE 16-25 and 24-50 F2.8 G lenses, we will find both the Sony G lenses are significantly smaller and lighter when compared to the APS-C lens. There is little to no advantage of the F1.8 aperture on the Sigma zoom, over the F2.8 aperture on Sony’s full-frame zooms, because the use of a full-frame sensor has inherently shallower depth of field and a one-stop high-ISO advantage. Some may see the maximum reach of Sony’s FE 24-50mm lens no match for the 40mm reach of the Sigma lens when the 1.5x crop factor is applied (giving it a 60mm full-frame equivalent angle-of-view). This would, however, ignore the fact that when shooting with a full-frame camera we can switch to APS-C, mode, giving a total zoom range for the Full Frame lens of 24-75mm (compared to 25.5-60mm).
We could also compare this new Art lens with the Sigma 28-70 F2.8 DG DN Full-Frame lens which has a much bigger range than the Sigma Art lens and no need to switch to APS-C mode. In both instances the Full Frame combinations are lighter and smaller than the APS-C camera with Sigma 17-40 attached.
A photographer choosing to shoot with an A7Cll or A7CR and the Sony lens also has an advantage because of the superior IBIS (SteadyShot Inside) found in the A7Cll and A7CR cameras and the Dynamic Active SteadyShot (courtesy of the Firmware 2.00 upgrade) compared to the Active SteadyShot found in the A6700 camera.
My feelings towards this new Sigma lens are mixed. I feel the 17-40 F1.8 DC Art is a welcome addition that only serves to increase the choice available for APS-C photographers, but it also serves to highlight certain advantages of using a full-frame system. There are many lightweight APS-C lenses that highlight advantages for using an APS-C system but the Sigma 17-40 F1.8 DC Art lens is not one of them. What I hope for in the coming years, is for Sony to release some innovative APS-C lenses to compete with Sigma’s F1.8 AP S-C prime lenses (and maybe some more compact zooms). All we can do now, is to cross our fingers and wait.
I will not be adding this new Sigma lens to my own APS-C kens lineup as the APS-C prime lenses I already own, together with the Sigma 18-50 and Sony 16-55 zooms, serve me well. If movie shooting is a priority for you, I would be tempted to wait for a Sony wide-aperture equivalent zoom lens which will allow you to get the maximum benefits from the in-camera Active SteadyShot and the impressive Dynamic Active SteadyShot which may appear in a possible firmware upgrade for the A6700 and/or Sony’s next APS-C camera.
Premium and Premium Plus Patrons might be interested to check out the 1-hour 'Full-Frame or APS-C' seminar and the 'Lens Choice 2' seminar where I discuss lens choice in great detail so Alpha photographers can make some educated decisions about purchasing the appropriate gear to meet their own needs and workflows.
Full Frame or APS-C: https://www.patreon.com/posts/99699910?collection=34689
Lens Choice 2: https://www.patreon.com/posts/81162455
Premium Plus Patrons can discuss this topic in more depth on the Q&A forum.