DxOMark has tested the EF 17-40mm f/4L USM lens, the result of this lens is good, close to EF 16-35mm f/2.8L II USM lens.
Compared to EF 16-35mm f/2.8L II USM lens:
Conclusion from DxOMark:
Due to its more glamorous sibling this modest lens is often overlooked though it’s well known for its high-performance by Canon users. As a small, light, highly portable zoom it would make a great choice for travel, landscapes and general-purpose photography. Although not exactly cheap at $839, if portability is a concern it’s a great alternative to the faster model.
Buy EF 17-40mm f/4L USM for $839.00 at Amazon/B&H/Adorama/ebay