"The Sigma 24-105mm f/4 is extremely well-built. It almost feels like a Zeiss lens. Autofocus is extremely quick throughout the entire range of the lens and image stabilization on this lens work wonders. Not to forget that the image quality of this lens is fantastic and that the lens is absolutely sharp. In the conclusion, the reviewer writes :
If I could only have one lens with me, this would be it. This lens.The Sigma 24-105mm f4. I emerged from testing this lens thinking this just may be the most well-rounded, practical lens I have ever used. It’s not about glitz or glamour. The Sigma 24-105mm f4 is about getting the shot. This lens is really good. It is civilized and can be put to work everywhere. Sigma put a lot of thought into this lens and it’s appreciated."
Well, I agree with the reviewer that the 24-105mm focal length is a great, well-rounded lens to have on a full frame DSLR but I am not convinced enough to ditch my Canon and rush out to buy the Sigma. Canon introduced the EF 24-105mm f/4L IS in 2005. Although in the subsequent years, there has been coatings and optics advancement, the perceptible difference in marginal improvement is very small, in my opinion. However, an additional one or two stop of IS improvements on the Canon would be greatly appreciated. I have owned the Canon EF 24-105mm f/4L IS for years and am very happy with it. You can see Travel and Wildlife photos taken with the lens worldwide on my website MichaelDanielHo.com