Why do people insist on posting images of bookshelves to demonstrate how "sharp" a lens is? There was not one detail in those images that was resolved differently by either lens, mainly due to the dearth of any high frequency detail that might show up resolution differences. If it wasn't for the distortion differences, I might have actually thought that they were samples from the same lens.
I think I'll wait for the results from Roger Cicala to decide whether the Sigma is a worthwhile upgrade. I would recommend that in future, you either do reviews properly or stop publishing this rubbish as CR's "official" review.
Out of 23 "reviews" this is the first and *only* time we posted photos of my dusty bookshelves. I certainly don't insist on it, or like it, but it does show difference of detail in the corners, vignetting and other real-world variables.
Roger is an incredible technical reviewer with all the right tools to measure and analyze lenses and I too look forward to his reviews and articles. I just pay less attention to the charts and more to how it works for me professionally. The final image is what matters to me and my clients. I'm also open to hearing your take on what entails a "proper" review for my future rubbish.
Please accept my apologies for my last comment, it was harsh and rude; I appreciate anyone who takes the time to post a review and take the flak for it!
I wouldn't expect anyone who isn't properly set up for it to attempt quantitative testing, nor given the number of technical review sites available, would I feel the need for it. I would prefer to see you use large crops from photos taken in your professional style, like the photos that you used to illustrate the review, to demonstrate your points.
I won't mention the name of the website that uses the "bookshelf-of-doom" to "show" lens "sharpness", suffice to say that I don't put any credence in their reviews!