Canon EOS 7D Mark II (G) Instruction Manual page 255

Effective Range of Built-in Flash
ISO Speed
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400
ISO 12800
ISO 16000
H1
(equivalent to ISO 25600)
H2
(equivalent to ISO 51200)
When you use the built-in flash, detach any lens hood and keep at least
1 meter/3.3 feet away from the subject.
If a lens hood is attached or if the subject is too close, the built-in flash
will be obstructed and the bottom of the picture may look dark.
Do not perform flash photography when the built-in flash is held down
with your finger or not fully raised for some other reason.
If you use a super telephoto lens or large-aperture lens and the bottom of
the picture looks dark, using an external Speedlite (sold separately, p.259) is
recommended.
EF-S18-135mm f/3.5-5.6 IS STM
EF-S15-85mm f/3-5.6 IS USM
Wide Angle: f/3.5
1-3.1 / 3.3-10.3
1-4.4 / 3.3-14.6
1-6.3 / 3.3-20.6
1.1-8.9 / 3.6-29.2
1.6-12.6 / 5.2-41.2
2.2-17.8 / 7.3-58.3
3.1-25.1 / 10.3-82.5
4.4-35.6 / 14.6-116.7
5.0-39.9 / 16.4-130.9
6.3-50.3 / 20.6-165.0
8.9-71.1 / 29.2-233.3
D Using the Built-in Flash
(Approx. in meters/feet)
Telephoto: f/5.6
1-2.0 / 3.3-6.4
1-2.8 / 3.3-9.1
1-3.9 / 3.3-12.9
1-5.6 / 3.3-18.2
1-7.9 / 3.3-25.8
1.4-11.1 / 4.6-36.5
2.0-15.7 / 6.4-51.6
2.8-22.2 / 9.1-72.9
3.1-24.9 / 10.2-81.8
3.9-31.4 / 12.9-103.1
5.6-44.4 / 18.2-145.8
255