Sigma 18-35mm f/1.8 DC HSM review
The centre third of the lens is home to a focussed-distance window with markings in both feet and metres, together with an AF/MF slider that displays a white panel when AF mode is selected. This feature was welcomed in the previous 35mm f/1.4 review as it provides an ultra-quick way to confirm the focussing mode without having to read the markings adjacent to the switch. This advantage may not be fully appreciated by readers with perfect eyesight but those who wear glasses for reading, and an even wider cross-section of people when the light level falls very low, would quickly recognise its value when using the lens in the field. This is a little touch that offers no drawbacks but indicates the lens designer's ambitions to consider the needs of all users, not just the healthiest cross-section of buyers.
The rear of the lens contains the zoom ring, which sits well clear of the lens hood when the petal-type shade is reversed for storage. Given the modest zoom range, the rotation of about 75 degrees is ample to yield suitable control but the ring is placed slightly too far back to be truly comfortable in use. In addition, the mechanism felt a little stiff on the review lens.
Technical testing produced a very strong set of MTF results that showed the zoom performs best at its longest focal length. That said, its performances at 18mm and 24mm were also very good and should not be taken as being in any way disappointing. It might be said that having lower (but definitely not "low") resolution at the zoom's maximum aperture could be a significant failing in a lens that is being sold on its maximum aperture setting but there was no evidence from field testing to suggest that users will detect any visible sign of this slight dip.