posted on Mar 5, 2010 at 10:59AM
Head-2-Head Lens Review: Canon EF 16-35mm f/2.8L II USM vs. Canon EF 17-40mm f/4L USM
Subjective Quality Factor (SQF)By Ted Dillard
The Subjective Quality Factor (SQF) of the lens is a mathematically-derived rating that aims to characterise at how the image will appear to the eye, taking into account all the characteristics of human vision. Very simply, it is a rating to indicate how the optics will appear, even “feel” to the viewer at certain viewing distances.
Once again, we’re seeing the Canon 17-40mm f/4 lens take the slight edge on the 16-35mm f/2.8 at wide-open.
At two stops down, the results are even more dramatic. The EF 17-40mm f/4 appears sharper at