Sure just pass whatever ID or login you want.
You can even lookup multiple people at once
https://api.twitch.tv/helix/users?login=twitch&login=twitchdev
Will return, for example:
{
"data": [
{
"broadcaster_type": "partner",
"created_at": "2007-05-22T10:39:54Z",
"description": "Twitch is where we come together live to make our own entertainment. Unabashed fans, welcome home",
"display_name": "Twitch",
"id": "12826",
"login": "twitch",
"offline_image_url": "https://static-cdn.jtvnw.net/jtv_user_pictures/bdc19970-3a3b-4516-9f23-4203d59f0a5d-channel_offline_image-1920x1080.png",
"profile_image_url": "https://static-cdn.jtvnw.net/jtv_user_pictures/e3bf8782-a962-4829-afd0-6cc9c3853778-profile_image-300x300.png",
"type": "",
"view_count": 334996079
},
{
"broadcaster_type": "partner",
"created_at": "2016-12-14T20:32:28Z",
"description": "Supporting third-party developers building Twitch integrations from chatbots to game integrations.",
"display_name": "TwitchDev",
"id": "141981764",
"login": "twitchdev",
"offline_image_url": "https://static-cdn.jtvnw.net/jtv_user_pictures/3f13ab61-ec78-4fe6-8481-8682cb3b0ac2-channel_offline_image-1920x1080.png",
"profile_image_url": "https://static-cdn.jtvnw.net/jtv_user_pictures/8a6381c7-d0c0-4576-b179-38bd5ce1d6af-profile_image-300x300.png",
"type": "",
"view_count": 10944104
}
]
}