Is this SD card fast enough for 4K video on a mirrorless camera?

Hey Kendall! For 4K at 30 and 60 on a mid range mirrorless you want a card rated V30 and U3. That guarantees at least 30 MB per second sustained writes, which covers the typical bitrates for long takes. If your camera has an all I high bitrate mode you would need V60, but for most mid range profiles V30 is solid. Use a full size SD instead of a microSD in an adapter to reduce dropped frames.

Get SanDisk 128GB. It is a full size SD rated U3 and V30, so it can keep up with 4K without buffering or stopping & and it has been reliable for long continuous clips on many mirrorless bodies.

Think in terms of sustained write rather than the big burst number on the label.

For 4K 30 and many 4K 60 profiles your target is V30 with the U3 symbol which means the card can hold 30 MB/s continuously.

That covers most long GOP codecs up to about 150 Mb/s.

If your camera has an all I or high bitrate log mode that pushes past that range aim for V60 to give yourself headroom.

I once chased the biggest number on the box and kept getting drops on long takes and it drove me nuts.

Hi Kendall, Pick V30 with U3 for 4K at 30 and most 60, since the 30 MB per second floor keeps up with typical 100 to 150 megabit codecs to prevent dropped frames. Go V60 for high bitrate all intra and use a full size SD card instead of microSD with an adapter to avoid hiccups.

I shoot long ceremonies and interviews and the reliable setup has been a full size SD with a V30 and U3 mark. That keeps up with 4K 30 and the common 4K 60 profiles on mid tier bodies. For the rare high bitrate all I mode I swap to V60.

A few practical things that help avoid buffering. Format the card in the camera before important sessions. Do not run cards to 100 percent full because performance can dip near the end. Keep the slot door closed and the camera cool when possible since heat can slow cards. Do this and you should get hour long takes without stops. No drama.