Since quite a few of you seem to like interpreting photos, a few points.

You have to get a photo taken from an angle as close to 90° to what you want to guesstimate, in the case of dihedral, as close to directly in front or behind at datum level. There is no point in looking at Gaston's photo as it is taken from well above the datum and to the side. As the wing LE and TE on the Il-2 are not straight, any difference in angle above or below horizontal brings this plan view kink into play and makes it impossible to gauge dihedral by looking at the LE or TE.

This photo from the Squadron In Action, taken from behind but slightly above the datum is better for seeing the dihedral change on the top surface. It is low contrast, but if you place a straightedge on the top surfaces of each side of the centre section and extending to the tip, you will see the slight dihedral.

Aerodynamically speaking, dihedral is effective as a stabilizing force from pressures on the bottoms of the wings. The decreasing thickness from root to tip add up to the effective dihedral. Just sayin'.

Dihedral provides lateral stability insomuch as any yaw or wing drop will increase the lift on the advancing wing and reduce it on the retreating wing which produces a rolling couple. This rolls the aircraft against the yaw and levels an aircraft which is side slipping - more dihedral, the stronger the effect, but too much dihedral and too little fin area will produce Dutch rolling, where the aircraft snakes and rolls from side to side The fin and rudder provide directional, or weathercocking, stability.

Swept wing aircraft need less dihedral than straight winged aircraft as the sweep on the advancing wing effectively produces more lift even with zero dihedral, but are more prone to Dutch roll than straight wing aircraft.

BTW, Chuck, I enjoy your cartoon assisted builds - great stuff!