..continues from here. Even though I am using EF 17-40 on Canon FF camera, I was really surprised to see just how wide 10mm is. Below is the comparison between 18mm and 10mm. Drawing an outline of the 18mm area really gives a "true picture" (no pun intended) of the difference. If you thought Sigma 19mm or even SEL16F28 was wide, look at this, sheesh. Here are a few shots I took yesterday with this lens.