Customize your Netflix account settings
If you suspect your picture quality isn't what it should be, the first thing to do is check your own Netflix account's streaming settings. To do this, head to My Accounts > My Profile, tap Playback Settings, and make sure you've selected "High," as that's the only setting that will enable you to see things in HD or Ultra HD (assuming the TV/tablet/phone/laptop you're watching on supports 720p resolution or higher).
Watching in Low or Medium is fine if you don't want to blow through data on a mobile device, and Auto can prevent obnoxious buffering stalls by throttling the quality based on your current connection speed. But there are better ways to manage those issues (more on that later).
Also, if you subscribe to Netflix's lowest-tier $7.99-per-month streaming plan, you're actually only capable of streaming content in Standard Definition (SD). If that's you've been craving a more vivid experience, consider splurging an extra two bucks for the HD. Note: once you upgrade to high-def, it may take a few hours to take effect.