Messerschmitt Bf.109F - German users, part one

The development of the Bf.109F had begun in 1939. After February 1940 a new engine, the DB 601E had been developed to be used in the Bf.109. Engineers of Messerschmitt took two Bf.109Es airframes and fitted the new engine in them. That way, the first two prototypes, dubbed V21 and V22, kept the trapeziform wing shape of the Bf.109E, but by "clipping" the tips, total wingspan was reduced by 61cm (2ft).
V22 became in fact the testbed for the pre-production version of the new DB601E engine. Smaller wings had detrimental effect on the handling so V23, a new prototype was fitted with new, semi-eliptical wingtips, which would become the standard wing planform of all Bf.109 versions. A fourth prototype was built, V24, flew with the clipped wings but with a modified "elbow"-shaped supercharger air-intake which was chosen for production, and a deeper oil cooler bath beneath the cowling. On every of these prototypes, fuselage was cleaned up and engine cowling was modified to improve aerodynamics.

Sources:
1. https://en.wikipedia.org/wiki/Messerschmitt_Bf_109_variants#Bf_109F
2. Signal Squadron - Aircraft In action 57 - Messerschmitt Bf-109 in Action Pt.2
3. Salamander Books - The Comple Book of Fighters