9 out of 10 points and recommendedOptically very good with excellent build qualitySome barrel distortion at 20 mm. Not HSM
Sigma has produced an excellent 2x wide angle zoom lens with the 20-40 f2.8 EX DG.reviewed November 5th, 2005
While the range may not suit users of DX (APS-C format) cameras, it is very useful for full-frame film or digital. By not going ultra-wide, Sigma has avoided the corner softness that often affects such lenses. Throughout the range, sharpness is excellent, contrast is good and colour is good albeit slightly warm. This is also a lens that is not prone to vignetting; there is only very slight vignetting wide open at the wide end and no vignetting at the long end.
A disadvantage is that at 20 mm there is some barrel distortion but it is not excessively significant. In Photoshop CS2 is is necessary to correct the distortion by 1% to 2%.
Auto-focus is accurate. This lens does not have a High Speed Motor and consequently there is no full-time-manual focusing when in auto-focus mode. To implement manual focusing youhave to pull the focus ring towards you and also set the AF/MF switch to MF. Despite the lack of HSM, focusing is fast.
I would highly recommend this lens to anyone looking for a zoom lens in this range.
5 out of 10 points and recommendedA nice little travel lens, better than you might think.Flare at w/a, auto-focus a little tricky.
This is the latest incarnation of Sigma's popular 7x zoom for film cameras (and full frame digital too, perhaps). It's a "twin" of the well-thought-of 18-125 for DX digital cameras and has much the same characteristics.reviewed November 5th, 2005
You need to stop it down for good image quality. Wide open it's soft in the corners and while it's usable for film it's unacceptable on a full-frame digital camera under about f8. Overall image quality is above-average for this type of consumer zoom.
Auto-focus is tricky at wide angle. The trick is to zoom in to focus and hold the shutter button halfway while zooming out to compose the shot. Focus using this method is usually spot-on.
Without the lens hood (supplied) it is very prone to flare at the wide end (as is the 18-125).
The benefit of this lens is that it covers a very good range, you can leave it on the camera all day and if you pay attention to the aperture and the focus method you will get good pictures.
[Tested on Canon EOS 33 and Canon 5D]
8 out of 10 points and recommendedSharp, bright, good soft focus effect if required.None I can think of.
This lens is a hidden gem. You will only find it on the shelves of specialist dealers. It's less than a third of the price of Canon's 135 f2L and comparable optically.reviewed November 6th, 2005
Without the soft focus engaged the lens is sharp over the frame. On an APS-C camera it has a field of view equivalent to 200 mm so you can use it for sports and it will take Canon (or Sigma) teleconverters to extend the reach. On full-frame it is an ideal portrait lens and useful for street candid shots. It's fairly light (390g) and unobtrusive.
The soft focus effect only works at apertures from f2.8 to f4. The soft focus ring has two click settings but you can set it between the stops. A setting of 1 at f4 produces a dreamy but focused effect that's hard to achieve with software.
I also use it as a macro lens with an extension tube.