Canon SPEEDLITE EL-1 Advanced User's Manual page 107

Difference between Radio Transmission and Optical
Transmission
Wireless shooting using radio transmission provides some advantages over wireless
shooting using optical transmission, such as less interference from obstacles and not having
to point the receiver's wireless sensor toward the sender unit. The main functional
differences are as follows.
Function
Transmission distance
Firing group control
Receiver control
Channel
Wireless radio ID
Receiver controls
* 1-3: Restrictions exist depending on the camera (*1:
Camera Used, Shooting in a Different Flash Mode for Each
from a Receiver Unit, *3:
Radio transmission
Approx. 30 m / 98.4 ft.
Test flash
Modeling flash
Release
Remote Release from a Receiver
1
Up to 5 groups *
(A, B, C, D, E)
Up to 15
Auto, Ch. 1 - 15
0000 - 9999
○
2
○ *
3
○ *
Restrictions on Functions Depending on the
Group, *2:
Unit).
107
Optical transmission
Approx. 15 m / 49.2 ft. (indoors)
Up to 3 groups
(A, B, C)
No restriction
Ch. 1 - 4
–
–
–
–
Test Flash / Modeling Flash