Lens Comparison at 55mm

EF refers to the EF 28-80mm f/3.5-5.6 IV, while EF-S refers to the EF-S 18-55mm f/3.5-5.6 II, and Sigma refers to the Sigma 17-70mm F2.8-4 DC Macro OS HSM.

The 7D camera was set to ISO 100. All lenses were set to approximately 55mm focal length, physically supported and used without image stabilisation. Two regions were compared as highlighted here:

f/5.6 EF EF-S Sigma EF EF-S Sigma

The 28-80mm lens is showing chromatic aberrations, the Sigma seems to have slightly better contrast than 18-55mm, but at the same aperture has a narrower depth of field as seen by the blurring of the trees behind the roof.

f/9 EF EF-S Sigma EF EF-S Sigma

Again the 28-80mm is showing slight aberrations, and possibly the 18-55mm is too? The 18-55mm lens and Sigma are roughly the same sharpness in the centre, but the Sigma wins at the edge of the frame.

f/20 EF EF-S Sigma EF EF-S Sigma

All three lenses look fairly similar at f/22, but the Sigma is ahead for contrast and colour.

f/32 EF EF-S Sigma EF EF-S Sigma

f/32 might slightly favour the Sigma, but all three lenses are a little fuzzy now. The colour and contrast on the Sigma look the best.