Almost all cameras use removable memory cards to store photos and video. A few smaller devices use fixed in-built memory instead, but these are relatively rare.
Memory card types
Memory cards come in many different types, though many have slowly been phased out and others are very specialised.
The most common type is the SD/SDHC/SDXC card. Physically these are identical, though the technology inside is different. SD cards are the oldest and rarely used now because they are quite slow and have limited capacity. SDHC cards are faster with a higher capacity, and the most common type overall. SDXC cards are the latest type and offer potentially the highest capacities and speeds. Older cameras may not be able to use the newer types, so check the specs.
SD cards come in two higher speed variants. UHS-I cards are designed for high-speed data transfer using the regular design, while UHS-II cards have an extra row of pins and even faster data transfer. You need a camera with UHS-II compatible card slot to take advantage of the speed of UHS-II cards.
Many action cams, 360 cameras and ‘wearable’ cameras use smaller microSD cards. These are about the size of a fingernail but otherwise follow the SD standard – you can insert a microSD card in a regular SD memory card slot using a simple low-cost adaptor. Many microSD cards come with an SD adaptor.
Before SD/SDHC/SDXC cards became so widespread, Compact Flash cards were popular, especially in enthusiast/pro cameras. These are larger and are no longer supported by many new cameras. A new CFast type offers higher speeds and capacities, but it looks as if it might lose out to other emerging formats, notably CFexpress.
CFexpress looks like it might be the next big development for fast, high-capacity memory cards. Physically, it’s identical to the XQD memory card format already in use in professional Nikon and Panasonic cameras. It’s likely that cameras that use XQD cards will soon be updated to use CFexpress cards.
A couple of memory card formats have fallen by the wayside. For a while, Olympus promoted its xD Picture card format, with memory cards about the same size as a microSD card, but these are no longer used. Sony makes its own Memory Stick and smaller Memory Stick Duo memory card type, but has long since swapped to memory card slots that take both these and regular SD/SDHC/SDXC memory cards, so that almost all users will use SD/SDHC/SDXC cards in Sony cameras as a matter of course.
Many computers and laptops have SD card slots for transferring photos and video directly; otherwise, it’s useful to have a card reader connected to the computer so that you can slot in your memory card and copy images across.
Memory card capacity
Memory card capacity is measured in GB (gigabytes) and is important for both stills and video photography. Many photographers shoot RAW files rather than JPEGs and these can take up a lot of space, particularly with the latest high resolution cameras.
Memory card capacity is also important for video, especially as 4K video is becoming the new norm and high end 6K and 8K cameras will follow.
Memory card speed
Memory card speed is quite important for stills photography but very important for video. In stills photography, a faster memory card means that the camera’s memory buffer clears faster after a burst of continuous shooting and it may even improve the buffer capacity a little. It also helps when copying large numbers of files to a computer.
Memory card makers will quote a card’s speed in terms of maximum read/write speeds. These are a useful indication of the memory card’s best possible data transfer speeds and its general performance, but are not helpful for videographers.
With video, memory card speed is much more important. This is because the video must be recorded to the memory card in real time – the camera’s memory buffer is no help here. What this means is that the memory card’s maximum speed is not as important as its maximum sustained speed. Videographers need to know that the recording speed will not drop below a minimum value. If it does, the camera will ‘drop’ frames and the video will appear to stutter.
This means that memory cards have a second speed rating, or ‘class’ rating. This specifies the minimum sustained write speed for the memory card. There are three main standard here.
For lower-end memory cards, there are Class 4, Class 6 and Class 10 ratings that meet the minimum requirements for standard HD video capture, full HD and basic 4K capture. Beyond this there are U1 and U3 ratings.
Confusingly, there are also ‘V’ ratings based on minimum sustained recording speeds, so that you can get V30, V60, V90 cards that can record at a minimum speed of 30MB/s, 60MB/s and 90MB/s respectively. These speed ratings are used mostly by professional videographers.
Right now, memory card speed ratings are confusing. ‘Class ratings’ work well enough for consumer cameras, ‘V’ ratings might be better for professional cameras and ‘U1’ and ‘U3’ ratings are somewhere in the middle.