Samsung's various models for the S21 aren't all the same. If the price and physical size didn't clue you in, the spec sheets likely did. And nestled among the list of different named standards and numbers is a curious tidbit that escaped detection on launch day: While the lower-end Galaxy S21 and S21+ support 960 fps super slow motion video (in bursts up to 0.5s), the ostensibly more premium S21 Ultra, with its upgraded cameras, doesn't — or least, it doesn't natively.

If that sounds familiar, that's because last year's S20/S20 Ultra had a similar arrangement.

It's not super straightforward if you aren't familiar with how it all works, but hidden in a footnote in the video recording section of the spec sheet, Samsung illuminates the difference:

"On Galaxy S21 5G and S21+ 5G, users can record approximately 0.5 seconds of video captured at 960 fps with approximately 16 seconds of playback. On Galaxy S21 Ultra 5G, users can record approximately 1 second of video captured at 480 fps and digitally enhance the video to 960 fps with approximately 32 seconds of playback."

Put simply, that means the smaller S21 models can record 960 fps natively, instead of relying on digital interpolation to create the frames between the 480 fps it can record, as with the S21 Ultra. In some cases, the difference probably won't be noticeable, but it gives the smaller models a leg up when it comes to recording slow-motion video.

The distinction is curious. As noted by Android Authority, there isn't a chipset-level difference between phones, and the Snapdragon 888 that these phones share (in the US) should support 960 fps capture at a hardware level.

After publication, Samsung told us that the reason for the S21 Ultra's digitally upscaled slow-mo video has to do with the phone's larger image sensor, which operates at a lower shutter speed when recording video. Rather than artificially limit the smaller phones, which can reach a higher shutter speed, Samsung elected to give them the full 960fps recording capability and use its frame rate conversion tech on the bigger phone, implying that the difference between the two wasn't very perceptible.

I know this sounds like an odd explanation, but so far as we can tell, it's legit. This DP Review article detailing the difference between shutter types claims that the performance of electronic shutters (as you'd have with smartphone video), can be affected by not just pixel count, but pixel/sensor size, and the S21 Ultra does have a bigger primary sensor with a very high pixel count compared to the smaller S21 and S21+.

If you plan on using the feature, it might be a good idea to keep this distinction in mind when choosing a model. Though the "digitally enhanced" 960 fps is probably enough, slo-mo aficionados may be better served by the cheaper model.

Samsung has provided us with more details regarding the slow-motion video on the S21 Ultra, and confirmed that the larger sensor in the bigger phone is responsible for the difference in performance. Our coverage has been updated with these details.