There are four different Kindle ereader models available from Amazon right now (actually there are a lot more, but let’s just stick with the current lineup).
Of the four current Kindle models, three have frontlights, and each one is different. Some people call them backlights but since E Ink is opaque that doesn’t work.
Technically speaking they’re more like sidelights since they’re placed along the side of the screen (usually the bottom).
Then a light layer goes over the screen to distribute the light evenly (that’s the theory anyway; they haven’t quite mastered even frontlights just yet).
The entry-level Kindle is the only Kindle without a frontlight.
The Kindle Paperwhite was Amazon’s first ereader to get a built-in frontlight (they released it after B&N came out with the Nook Touch with GlowLight).
The Kindle Paperwhite is now in its third generation. The light has changed some since the beginning; it’s gotten more even since the first gen, but the core technology remains the same.
The Kindle Paperwhite features 4 LED frontlights embedded at the bottom of the screen. You can barely see them if you tilt the device flat and look down the screen. For the most part the Paperwhite’s frontlight is very even, but some shadowy cones can sometimes be seen around the LEDs, like with most frontlights.
The frontlight on the Kindle Voyage has 6 LEDs. Plus the Voyage has a flush glass display that seems to help illuminate the screen a bit more evenly, but the Voyage’s screen is sometimes known for having different-colored hues slightly visible under certain lighting conditions.
The Kindle Voyage also adds an Auto Brightness feature that automatically adjusts the frontlight based on ambient lighting conditions. Additionally there’s a Nightlight feature that gradually reduces brightness over time at night as your eyes adjust to the darkness.
For some inexplicable reason Amazon decided not to include the auto brightness feature on the $300 Kindle Oasis. The thing that separates its frontlight from the others is the fact that it has 10 LED lights for improved light distribution. Plus the lights are embedded along the side of the screen instead of the bottom, which is rather unique.
All the frontlights have a dial to customize the brightness, but the light cannot be turned completely off. Kindles are the only ereaders without an off option for the light so that makes them different.