Resolution when purchasing movies from the iTunes Store - DVD & Blu-ray versus SD & HD

Hello,

So I'm browsing the iTunes store on my iPhone 11 Pro and notice that movies and TV series are advertised as HD or sometimes SD. Given all the devices I might use for play back support a minimum of Full HD (1920 x 1080) and I have a fibre Internet connection, I wanted to know what "HD" means on the iTunes Store app. Assuming I don't have any configuration forcing the selection of SD media over HD and that my Internet connection is fast enough for practical downloading of GBs of data per hour (I don't tend to stream but watch offline instead).

It might sound like a dumb question at first but while modern offerings are commonly available up to 4K resolution, older films or TV series may never have been available even at Full HD. Really ancient stuff might be available as SD only, no matter how good your Internet connection and playback device.

First question. In common parlance HD can mean either 1280 x 720 pixels (aka HD) or 1920 x 1080 (aka Full HD). Which one does the iTunes Store app mean? I could not find any indication by tapping on the HD icon by each movie, searching the help or contacting Apple Support.

Next question. In the iTunes Store app what resolution in pixels does SD denote please?

Final question. Comparing to resolutions quoted outside of the iTunes Store app, would one be right to equate SD to DVD resolution and HD to Blu-ray resolution?

Please note that I've avoided the word "quality" because this is influenced by the accuracy and amount of data captured per frame in the first place as well as other factors (clearly image quality will vary from one movie to the next when two movies may have been originally captured on film in different decades). What I'm really trying to grasp is how Apple's resolutions compare to the terms one might find quoted on physical media.

Many thanks in advance for any advice,

Andrew

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