The other limitation I see in the 18-35 f/1.8 is the limited focal length range relative to the other APS-C-only 17 or 18mm to something zoom lenses. While I'm loving what Sigma is doing with their lenses right now, I'm not yet a fan of limiting the usefulness of a lens to one of these categories

Frequently, wide aperture lenses used on the largest sensor format camera they support, show significant amounts of vignetting – which negates some of the wide aperture advantage. There's a comment in the introduction part of this review that doesn't make sense to me. I think it's wrong, but perhaps I'm missing something. Dpreview states, "it will also offer effectively the same light-gathering capability as an F2.8 lens on full frame", "meaning the same total amount of light is used to capture the image", "APS-C shooters will be able to use lower ISOs... substantially negating one of the key advantages of switching to full frame." From this example, we can see that the 9-blade aperture delivers rather smooth out of focus highlights with a touch of bright edge. New cameras may or may not work with this lens, and off-brand lens makers only sometimes will update lenses to work on new model cameras. Even though the diaphragm is round at large apertures, sunstars are quite good at moderate to small apertures. Bravo!With the sun in the corner of the frame, the Sigma 18-35 shows very little flare from a wide open f/1.8 aperture. Only the ribbed rubber surface portion of the zoom ring extends beyond the lens barrel diameter and Most 16, 17 or 18mm-to-something-mm lenses show very noticeable barrel distortion at their widest focal length. Flare slowly increases as the aperture narrows until becoming noticeable at f/8 and by f/16, strong flaring is obvious. Bokeh is a word used for the out-of-focus areas of a photograph, and is usually described in qualitative terms, such as smooth / creamy / harsh etc. In the Sigma 18-35mm F1.8 DC HSM lens, Sigma employed an iris diaphragm with nine rounded blades, which has resulted in very nice bokeh in our view. We do realise, however, that bokeh evaluation is subjective, so we've included several 100% crops for your perusal.

What makes a standard lens ideal for you? Certain important qualities are required, such as fast maximum aperture, versatility for snap shots, portraiture and indoor photography plus a good combination of a wide range of focal lengths in a compact design. SIGMA 18-35mm F1.8 DC HSM is the first zoom lens ever to achieve a maximum aperture of f1.8 throughout the zoom range. It is a wide aperture, standard zoom-lens for digital single lens reflex camera's with APS-C size sensor's. *1The lens has a focal range equivalent to 27mm - 52.5mm in a 35mm format and it can cover the angles of view of multiple fixed focal length lenses. This wide aperture, standard zoom lens enables the photographer to expand creative possibilities on any occasion. Zooming to 24mm improves sharpness. At f/1.8 the lens scores 2,470 lines, and it peaks at f/4 at 2,690 lines. At 28mm the lens manages 2,457 lines at f/1.8 and improves to 2,562 lines by f/4. Zooming all the way in to 35mm delivers 2,399 lines at f/1.8 and peaks at 2,528 lines at f/4. Edge performance when zoomed in a bit is consistently good; better than 1,800 lines at every tested focal length and aperture. What makes a standard lens ideal for you? Certain important qualities are required, such as fast maximum aperture, versatility for snap shots, portraiture and indoor photography plus a good combination of a wide range of focal lengths in a compact design. SIGMA 18-35mm F1.8 DC HSM is the first zoom lens ever to achieve a maximum aperture of f1.8 throughout the zoom range. It is a wide aperture, standard zoom-lens for digital single lens reflex camera's with APS-C size sensor's.The lens has a focal range equivalent to 27mm - 52.5mm in a 35mm format and it can cover the angles of view of multiple fixed focal length lenses. This wide aperture, standard zoom lens enables the photographer to expand creative possibilities on any occasion.By the way, you may enable Movie Cropping and shoot “4K Crop” video with any lens, not just APS-C. I’m simply pointing out that — unlike still photos — 4K video on the R5 is higher quality than you may expect. No overheating in 4K Crop The were 15 other identical images, but I couldn't see the point of boring you with the rest of the samples. It is easy to overlook any focal length range deficiencies when getting an f/1.8 max aperture available over the entire focal length range. This lens is too big and heavy for what it does, and its zoom range is foolish. 18-35mm is very useful for full-frame —but this lens can't handle full-frame; it only works from 28mm to 35mm on full-frame. That performance is from a very low DPP sharpness setting of "2" – the lowest setting I regularly use with the 60D.

I have not tested this on Canon, which would not be able to correct it without a lens profile, which does not exist. In this set of evaluations, we’ve compared the Sigma zoom with the highest performing full-frame primes of the same focal lengths – 18mm, 24mm and 35mm. While it might seem a little unusual, the lenses (all high speed models) reflect the state of the art in that format and when mounted on an APS-C DSLR offer the same angle of view (at each focal length) as the Sigma. The "DC" ("Digital Camera") in the name means that this lens is compatible only with ASP-C/1.6x FOVCF sensor format DSLR cameras.

Sigma provides as many focus distance markings as can reasonably be fit into the space available for them in the window. Unlike a prime lens with a single focal length, the Sigma is variable. You may zoom in-and-out without physically moving your camera setup. This offers greater flexibility, speed and creative control when composing a shot — especially when mounted on a tripod. One problem we might expect to see, given the lens's sheer physical length, is shadowing of the built-in flash at wideangle. This is indeed visible; on recent SLRs like the Canon EOS 700D, which lift the flash quite high above the lens, we saw some shadowing right at the bottom edge of the frame at focus distances. At the distances you'd most likely use the flash (~2 metres) it's pretty minor though, and effectively disappears if you zoom in a little bit, to just 20mm. With a minimum focusing distance of 28cm and a maximum magnification ratio of 1:4.3, this lens is excellent for close-up photography.