In an exclusive video we give you the lowdown on memory cards. Discover all about card types, classes, read and write speeds, plus what to consider when buying and using memory cards

With a huge range of cameras – from compacts to digital cinema cameras – now offering video shooting at HD or 4K the choice of memory cards to use is perhaps more crucial than ever. In this video we’ll take a look at the different types of memory cards, what the classes of memory card mean, their speeds and what to consider when buying memory cards for shooting video…

Card formats
The two most common card formats have been Secure Digital (SD) and CompactFlash (CF) cards. SD cards are used in all types of cameras – from point-and-shoots to pro digital cinema cameras. The smaller microSD cards are now often utilised in cameras such as HD camcorders and aerial cameras. CF cards are more robust and durable and are often used in pro DSLRs and cinema cameras.

Many of the current cameras that record digital video offer dual memory card slots. For example, the Canon EOS 5D Mark III DSLR includes one SD card slot and one CF card slot, whilst the EOS C100 Mark II digital cinema camera features two SD card slots. Probably the key advantage of dual card slots is that once one card is full of data you can continue recording to the other.

Read and write speeds
The speed of a memory card pertains to both its read speed and its write speed. Write speeds describe how quickly images or video can be saved to a card. The read speed denotes how fast data can be retrieved from a card – for example, when transferring footage to a computer. Generally read speed is always faster than write speed but write speed is absolutely essential for video as you will need your cards to have both the speed and capacity to deal with recording large amounts of digital video data.

Speed classes explained
Speed is shown on cards with either a multiplication value – each ‘x’ value represents .15MB/sec, so 2000x multiplied by 0.15MB/sec denotes 300MB/sec – or the more recent Class rating. The speed Class rating was based on requests from movie and video companies as video recording in different formats and resolutions requires certain write speeds when recording to a card. The Class ratings denote the minimum write performance to record video – a Class 2 card can handle sustained writing of data at 2MB/sec, a Class 4 card will handle 4MB/sec and so on… up to Class 10 as the fastest.

There are also so-called ‘UHS Speed Classes’, which indicate how quickly video content can be transferred onto a memory card. UHS-I enables maximum transfer speeds of 104MB/sec, while UHS-II enables speeds of up to 312MB/sec. Within the UHS Speed Class there are two designations, U1 and U3, which represent minimum write speeds of 10MB/sec and 30MB/sec respectively.

The CFast era
As you’ve no doubt gathered, speed is of the essence for shooting video and CFast 2.0 cards are the current leaders in terms of speed. The original CFast 2.0 card, launched in 2013, promised read speeds of 450MB/sec and write speeds of up to 350MB/sec. Both CFast and XQD cards were created by the CompactFlash Association to replace the CF card format as it had reached its maximum performance capabilities. In their current 2.0 versions XQD cards have a theoretical limit of 500MB/sec and CFast cards 600MB/sec. Both are ideal for shooting 4K video and beyond.

When buying memory cards for shooting video you should always consider the following:

What your camera supports
It may seem obvious but you should be aware of the fastest card speed that your camera supports. Check the instruction manual or manufacturer’s website to ensure your card matches what the camera is capable of.

The required write speed
For write speeds memory card maker SanDisk recommends Class 2 cards for standard video, Class 4 for HD Video, Class 6 and upwards for Full HD video, UHS U1 for Full HD video supporting real time video recording and U3 for Full HD and 4K Video supporting real time video recording.

The maximum capacity you’ll need
Ask yourself how long you plan to shoot for and how many cards you’ll need to do so? Make sure you have enough storage capacity to cover your shoot. You never want to be caught short of storage when shooting, so always bring one extra card above your estimated capacity!

The best card reader for your workflow
Buying the fastest memory card available won’t do you much good if you have a slow reader. For example, if your computer has a USB 3.0 port, buy a good USB 3.0 reader to take advantage of fast read speeds. This can save you significant time when transferring your footage and means you can start on your edit much sooner.

To find out more just click on the video window at the top of this page to watch our exclusive video on memory cards…