In the SPARK manual DJI recommends
Sandisk,
Kingston, and
Samsung "
UHS-1" SD Cards.
UHS-1
In 2010, the classification for the bus interface "
UHS" (
Ultra
High
Speed) was presented.
UHS-1 is the successor to the previous
Normal Speed (speed classes 2, 4 and 6) and
High Speed (Speed Class 10).
SanDisk Extreme PLUS
- developed for Android smartphones, tablets and system cameras
- record in burst mode, videos in Full HD and 4K Ultra HD UHS
- speed class 3 and video speed class 30 for recording videos in 4K UHD
- up to(!) 100 MB/sec reading speed or 90 MB/sec writing speed for faster transferring and recording
- designed for and tested in extreme conditions; temperature resistant, waterproof, shockproof and X-ray proof.
SanDisk Ultra Plus
The only information I found in Google is "
up to 80 MB/sec".
Usually only the fastest value is mentioned in advertising statements and this mostly relates to the irrelevant READING speed.
But WRITING the data is important for videos and photos!
For example:
- When saving single photos for a panoramic montage, the next picture can only be taken when the current one has been written completely to the storage medium.
- With HDR recordings, at least 3 photos are recorded in a row.
- If the SD card is too slow, there will be a "data traffic jam"
For videos, the SPARK takes thousands of photos in an endless stream, each with 1280 * 1024 pixels.
Each pixel requires at least 3 bytes of storage space (information about red, green, blue), so each individual image requires at least 6.2 MB of storage space. 30 frames per second are recorded with the video, that makes 186 MB per second! With the usual 8-bit color depth, we get even more video data per second!
DJI bought the patented video coding format "H.264" not only for the Spark. (Manufacturer's advertising statement: "
H.264 is undoubtedly today's number one video codec. H.264 was developed to provide videos in first-class quality for mobile devices, 4K or 8K televisions, or is used in professional Content ingestion and post production and offers unparalleled compatibility and robustness of a sophisticated codec.")
This compression significantly reduces the data volume, so that the SPARK gets by with a video memory bit rate of just 24 Mbit per second. (The larger and newer DJI drones have a lot more to offer.) 24 Mbit/sec is actually only 3 MB/sec.
When I bought my SPARK I inserted an old SD card into the slot, a slow one that I no longer needed in my mobile phone. And the DJI Go4 app promptly complained that "A very slow SD card is inserted."
Now I'm using a "
SanDisk Extreme Pro" that can WRITE at 90 MB/s. That is far more than sufficient, but the card was on sale at a very affordable price.
I would always recommend the
fastest affordable SD card so that there are no delays in WRITING the image data on board of the drone. It doesn't matter whether reading out at home on the computer takes a few seconds longer or not.
Therefore always pay attention to the WRITING speed, which is for cheap cards usually significantly lower than the advertised READING speed. And you should be skeptical if only the READING speed is given or just a speed value that you don't know whether it relates to reading or writing.