We got some variable results with SD cards in some recent fieldwork – cameras not taking photos as regularly as possible, transfer rates not as advertised – and some research turned up even more disturbing news about SD cards and what to watch out for.
SD cards are cheap because they are fundamentally made of cheap, error-prone memory, and rely on a microprocessor in each card that manages the data and thus what your computer sees. This has huge security consequences. Watch the youtube video in the link.
There are hacked SD cards that are labelled at high capacities, will report a higher capacity when plugged into your computer, but actually have a fraction of that capacity available.
- Capacity, classes and speeds must be checked with real-world tests.
- Sustained write and read speeds vary from advertised.
- Actual size of the card must be measured, and checked for errors.
- Formatting in your laptop may not prepare the card properly and can lead to problems – use a specialised application such as SD formatter or only format the card in your camera or other SD-specific device.
- This may not be really necessary, but doesn’t hurt.
This post will be updated with tools and code for testing SD cards; am experimenting with a few different tools.