Those who’ve bought a lot of movies from the iTunes Store got a pleasant surprise during last week’s keynote. Any movies which iTunes makes available in 4K will be available at that resolution to existing HD purchasers at no extra cost …

But MacRumors noticed an important piece of small-print in an Apple support document.

4K movies are only available for streaming.

If you’re watching on the new Apple TV 4K, the difference will be academic to anyone whose broadband speed is fast enough to cope. Apple says that you’ll need a minimum download speed of 25Mbps.

But if you have a slower speed, or were hoping to download 4K versions to watch offline on other devices, you’ll unfortunately be out of luck.

Don’t get too upset at Apple, though: it’s likely this is a restriction imposed by studios as a quid pro quo for allowing Apple to make the 4K streams available at no extra cost.

Photo: David Paul Morris/Bloomberg