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Closeups are generally speaking taken in Macro mode.
Since human eyes (except when immobilized for surgery by very fancy drugs not commonly available) have an inherent twitchiness to them, aside from blinking, you also need to set the camera to take pictures very rapidly, and thus with rather wide aperture.
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If not I shall explain further.
First put the camera in Macro Mode.
Then you can set the f/stop factor, or speed, and/or aperture (it varies from mode to mode, so you have to be in Macro Mode first.)
Are you in Macro Mode now?