Canon Speedlite 270EX - Manual (Page 13)

11
Flash head (normal position)
The Guide No. is 22/72 (ISO 100 in meters/feet). The
maximum flash coverage matches an EF 28mm wide
angle lens (EF-S 18mm).
Flash head (pulled forward)
The Guide No. is 27/89 (ISO 100 in meters/feet). The flash
coverage matches an EF 50mm (EF-S 32mm) or lenses
with longer focal length.
Switching Flash Coverage
When shooting with a lens wider than EF 50mm (EF-S
32mm), the periphery of the picture becomes extremely
dark.
See p.19 for guidelines about the flash shooting range.
COP
Y