Bryan Carnathan at The Digital Picture has posted his “Image Quality” results (ISO 12233 chart shooting) from the Sigma 24-105mm f/4 DG OS HSM Art.
It’s a good opportunity to talk about what we can learn from such a test.
The tool allows for direct comparison with another chosen lens. So let’s see how the Sigma lens fares over the zoom range against a direct competitor – the Canon 24-105mm f/4L IS USM.
The Sigma lens has better mid-frame and corner performance wide open. The famous L lens never really catches up as it is stopped down.
Wide open, the Sigma is superior again. Off-center and upon stopping down, the Canon fares a bit better than at 24mm, but never quite achieves the same level of contrast as the Sigma. Such a difference is not likely to be seen easily on real world pictures though.
Small differences here and there, but a tie overall.
The crops give a slight nod to the Canon for overall contrast wide open. Otherwise it’s a tie.
Wide open, the Sigma wins anew. However, the Canon recovers well from stopping down a few stops, whereas the Sigma barely improves.
The Canon has more clarity over most of the frame wide open. The Sigma catches up at f/8.
A bit puzzling, isn’t it?
Sure, but one has to take it for what it is: basically a black & white (lateral CA aside) contrast comparison of two lens samples at a single focusing distance. And it’s impossible to know whether some of the differences mentioned above fall within the unavoidable margin of error.
As paradoxical as it may sound, when two lenses are so close in specs, I find these chart shootings to be marginally useful, only to see if a lens really trounces the other contrast-wise, which is not the case here and quite rare with today’s lenses by the way.
Aside from that, overall rendering, color correction, bokeh, field curvature, distortion, coma, flare, etc… are what makes the image quality, and they cannot be assessed by shooting a fixed flat black and white chart. Extensive “real world” use of the lens is mandatory for that purpose.
Let’s wait for Bryan’s full review – it will be much more instructive.
Buy the Sigma 24-105mm f/4 DG OS HSM at: B&H Photo (the EF mount version is in stock as I write these lines) | Amazon