Canon SPEEDLITE 220EX Instructions Manual page 22

FP Flash
High-Speed Sync Guide Number Table
Shutter Speed
ISO 100
1/125 13.3/43.6
1/180 12/39.4
1/250 10.7/35.1
1/350 9.1/30
1/500 7.7/25.3
1/750 6.5/21.3
1/1000 5.4/17.7
1/1500 4.6/15.1
1/2000 3.8/12.5
1/3000 3.2/10.5
1/4000 2.7/8.9
• The Speedlite 220EX Guide Number changes
according to the high-speed sync operations. The
flash range decreases as the shutter speed
increases with FP flash.
• The limit of the flash range can be calculated with
the following formula: Guide Number ÷ the dis-
tance calculated from the aperture setting.
22
Guide Number (m/ft)
ISO 200 ISO 400
18.8/61.7 26.6/87.2
17/55.8 24/78.7
15.1/49.5 21.4/70.2
12.9/42.3 18.2/59.7
10.9/35.8 15.4/50.5
9.2/30.2 13/42.6
7.6/24.9 10.8/35.4
6.5/21.3 9.2/30.2
5.4/17.7 7.6/24.9
4.5/14.8 6.4/21
4/13.1 5.4/17.7