The length of time of which the eyes stop—the duration of the fixation—varies considerably from person to person.
眼睛停留的时间，即注视的持续时间，因人而异。
2
The length of the stops, when the eye fixates, varies from about 100 to 600 milliseconds and during this stop the brain starts to process the visual information received from the eyes.
当眼睛注视时，通常需要100至600毫秒，在每个点注视时大脑就开始处理从眼部接受到的视觉信息。
3
Camera lenses have two general attributes: f-stop and focal length.