While I had my Sigma 24-70mm f2.8 lens, and since I almost knew that I wouldn’t be keeping it for very long, I thought it would be a good thing if I were to compare the Sigma with the next lens I replaced it with – whatever that may be. The lens it replaced is the Canon 28-105 f3.5-4.5 USM MkII lens, and here’s my thoughts on both lenses

The Sigma 24-70mm f2.8 EX DG Macro
First impressions of this lens were – wow its massive. Its heavy, large and feels very expensive. The f2.8 throughout the zoom range appealed to me a lot and the fact that the barrel does not rotate upon focusing was another bonus. After using it for a short while I found that it was sometimes missing focus, for example, if something happened quickly I just grabbed the camera turned it on and pressed the shutter button. I heard it beep, so its in focus – right? But it wasn’t. The shot was missed.

I did some testing with this, and found that wide open at f2.8 at 24mm was VERY soft. Unusable photos. I am not sure if this is simply because its "being soft" at f2.8, or if the lens has back-focus problems. Either way, I wasn’t pleased. f2.8 at the telephoto end (70mm) seemed to be OK, still a little soft, but the photo’s were certainly usable for me. Anything above f2.8 and its pin-sharp at all focal lengths.

Apart from those problems, this lens seemed to be great. I liked the fact it was large, I felt like a professional photographer, and my camera looked like one. The focus speed wasn’t too bad. It was slow, and it is noisy, but I could live with it.

The Canon 28-105mm f3.5-4.5 USM MkII
I was planning on replacing the Sigma (above) with the Canon 28-135mm USM, but Jessops didn’t have any in stock, and I desperately wanted a lens in this range on the day I went looking for it. First impressions with this lens is the fact that its so tiny and light compared to the Sigma. Its roughly the same dimensions as the Canon 18-55mm kit lens when set at 28mm.

First time using this, I found the focus to be – WOW – insanely fast. Incredible focus speed, so so so quick and so quiet. I have the 18-55mm USM kit lens as well as the Canon 75-300mm USM lens, but both of those are no where near the speed of this. It hasn’t yet missed a beat on focusing, and all the photo’s I’ve taken so far (about 80) are all pin-sharp.

Compare time
And finally, along side each other, here is a comparison between the two lenses above. Its not exactly the best comparison ever, since I didn’t set the focal distances to all the same, but it gives you a good idea.

Conclusion?
Without doubt, the 28-105mm is the sharpest. I know this review/test isn’t the greatest one out there, but its from my personal experience with all these lens’s – no ball. You can quite clearly see that the Sigma is off focus at 70mm f2.8 and again at 24mm f2.8. Smaller apertures on this lens don’t seem to have this problem, but have it wide-open and its bad. The Canon is also sharper with smaller apertures (as you’d expect from any lens) but even when wide-open, the sharpness is still bearable, and a quick sharpen in your favorite photo editing software will sort this no problem.

If you want to ask a question, just comment below and I’ll reply to you.