Sigma A 24-105 mm f/4 DG OS HSM
- solid and stylish casing,
- very high image quality in the frame centre at all focal lengths,
- good image quality on the edge of the APS-C/DX sensor,
- decent image quality on the very demanding edge of full frame,
- very good correction of the longitudinal chromatic aberration,
- slight distortion at longer focal lengths,
- low astigmatism,
- negligible vignetting on the APS-C/DX sensor,
- efficient image stabilization,
- good, sensible autofocus.
- significant vignetting on full frame,
- high chromatic aberration near the maximum relative aperture at the shortest focal length,
- pronounced wide angle distortion on full frame.
Once again the Sigma company proved they can produce a high quality lens. Although it is not always able to compete successfully against its brand-name rivals (failing to do so when it comes to the chromatic aberration, vignetting or autofocus), in most categories it still gets higher notes. It gives you sharper images in the frame centre, it is more even and provides useful images also on a very demanding edge of full frame without the necessity of stopping down the aperture. For a lens with such parameters it is a huge achievement; neither the Canon nor the Nikkor managed to perform so well and here the Sigma truly deserves a standing ovation for its performance.
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Now I admit I saved the fly in the ointment for the very end. The Sigma 24-105 mm wasn’t the object of rumours and speculations because, to tell the truth, nobody expected and/or needed it. Launching it on the market is a bit like trying to compete with a stronger opponent against the odds. Let’s face it – the rival lenses, produced by Canon and Nikon, are very solid; it’s true that they are hardly flawless but still they can be called a very well done constructions. The situation of the Sigma is especially difficult when it comes to the Canon line-up; not only the EF 24-105L is cheaper than the Sigma on its own, you can also buy it in a kit with a camera for a very affordable price. The Nikkor is a bit more expensive than the Sigma but it comes with a wider focal range and smaller filters, 77 mm in diameter, which are cheaper and more common than the 82 mm ones you need for the Sigma.
To sum up: if you buy the Sigma 24-105 mm OS you will enjoy that lens for sure. The question is how many people decide to do so when the brand-name competition is so strong and the prices in that segment -very similar. The time will show…