SANTA MONICA, Calif. Buying movies and TV shows to watch on the Kindle Fire will be a lot more appealing now that Amazon’s tablet computer sports a much more vibrant screen.

The screen in the Fire’s new HD models is such a major improvement that I can’t see why you would purchase a regular model, even if it means saving $40.

The HD models were among the new devices Amazon unveiled Thursday. They start at $199 for the smaller one, with a screen that measures 7 inches diagonally. Those will start shipping Friday. Two models with larger screens will go on sale in November.

Amazon is also refreshing the regular model. It promises to be 40 percent faster than the original one, which came out last November. It comes with a price cut to $159, instead of the original $199. The regular Kindle Fire also will start shipping Friday.

The new offerings bring the HD Fire into closer competition with Apple’s market-leading iPad. The HD screens will have a higher resolution than the regular Fire, just as Apple introduced a higher-resolution screen earlier this year. The larger models will have 8.9-inch screens, slightly smaller than the iPad’s 9.7 inches.

By the numbers, the difference between the HD and the regular screens doesn’t seem that big.

The smaller Kindle Fire HD has a screen resolution of 1280 by 800 pixels. Both last year’s 7-inch model and the upgraded regular version with better innards have screens with 1024 by 600 pixels.

That doesn’t come close to the latest iPad, which has a resolution of 2048 by 1536. Nonetheless, this upgrade feels like a big leap for Amazon. It means a sharp picture instead of one that seems made up of lots of pixels, a welcome relief that feels even better when you consider the price. At $199, compared with $499 for the latest iPad, I can see this being a popular stocking stuffer this Christmas.

Amazon has also made a couple of important design changes in its new HD models. For one, the speakers are now on both sides of the device when held in landscape mode like a movie screen, meaning you can watch movies in Dolby Digital Plus stereo sound without headphones. The old Kindle Fire had stereo speakers off to one side when held that way, and that hasn’t changed with the upgraded non-HD model.

Both the upgraded Kindle Fire and the new HD 7-inch models also come with a full suite of new features that are nifty but not game-changing.

Both devices will feature the X-Ray series of features that provide insights into the book or movie you’re enjoying.

An on-screen tap during a movie will list actors in the scene. With more clicks, you can learn more about them from Amazon’s movie information service IMDb. In books, X-Ray has been a popular feature on the Kindle Touch e-reader. That now works on Kindle Fire and gives you a bird’s eye view of where characters or ideas appear later on in a book.