Canon EOS 90D, Instruction Manual, Page: 426 / 888

214
ISO Speed Settings for Still Photos
o
Image noise (such as dots of light or banding) may increase and apparent
resolution may decrease at H (equivalent to ISO 51200), because this is an
expanded ISO speed.
o
ISO 100/125/160 or an expanded ISO speed cannot be selected when
[
z
: Highlight tone priority]
is set to
[Enable]
or
[Enhanced]
(
=
219).
o
When shooting with a high ISO speed, high temperature, long exposure, or
multiple exposure, image noise (rough grain, dots of light, banding, etc.),
irregular colors, or color shift may become noticeable.
o
When shooting in conditions that produce an extreme amount of noise, such
as a combination of high ISO speed, high temperature, and long exposure,
images may not be recorded properly.
o
If you use a high ISO speed and fl ash to shoot a close subject, overexposure
may result.