Difference between 20mm, 24mm and 30mm

The lady at Lozeau was trying to push me to get the 24mm instead of the 20mm (they didn't have any 20mm Sigma Art in stock). Glad I did find another shop in Montreal that had the 20mm! What a difference.

30mm (35mm equiv on FF) Also the iPhone equiv. mm.

24mm, not too bad. But what's the point ?

 20mm ! Now that is a much better picture!

20mm ! Now that is a much better picture!