7.2: Memory Cards
- Page ID
- 151242
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Choosing the Right Memory Card
When planning to record video, it is important to know what memory card to choose for your camera. The instruction manual for your camera will tell you what memory cards are compatible, but it is good to know the most common types of memory cards on the market and to make sure you get the right one for your production. Choosing the wrong card can hinder or completely stop production.
Memory Card Form Factor
The most common types of memory cards for DSLRs and prosumer video cameras are:
- Secure Digital (SD)
- Compact Flash (CF)
- MicroSD
When you start working with high-end professional cameras, you will have to use solid-state flash drives created for specific cameras or CFast cards, which are not interchangeable with the CF cards listed above.
Card Capacity for Video Recording
Not all memory cards are the same. For example, SD and MicroSD cards come in four different formats:
- SD has a storage maximum of 2 GB
- SD HC (High Capacity) has a storage maximum of 32 GB.
- SD XC (Extended Capacity) has a storage maximum of 2 TB
- SD UC (Ultra Capacity) has a storage maximum of 128 TB
The memory capacity needed for a memory card will depend on the video format size you choose and the file size. You can look for bit rate and file size in the user manual for your camera. For example, the Canon T8i DSLR can record in 4K UHD at 24 or 25 frames per second with a bit rate of approximately 120 Megabits per second (Mbps) or approximately 861 Megabytes per minute. For every minute of video recorded, you will use about 861 MB of memory. To choose the right memory card capacity for your production, you need to decide how much recording room you need. For the Canon T8i:
- A 32GB SD card can record about 35 minutes of video
- A 64GB SD card can record about 70 minutes of video
- A 128GB SD card can record about 2 hours and 20 minutes of video
Keep in mind that these are approximate times for the Canon T8i DSLR. Also, these calculations do not account for the audio being recorded.
It is in your best interest to carry more than one memory card with you on a video shoot. If one card breaks or stops working, you will have a backup. This will prevent delays in production and provide plenty of memory.
Read/Write Speed
Every memory card has different read/writes speeds. This indicates how fast information is read from the card and how fast information is written onto the memory card. SD cards display reading and writing speeds using Megabytes per second (MB/s).
We need to convert Megabits per second (Mbps) to Megabytes per second (MB/s). Megabits and Megabytes are not the same; for every 1 megabyte, there are 8 megabits. Using the example from the previous section of the Canon T8i, we need to convert 120 Mbps to MB/s by dividing 120 by 8, which is 15 MB/s. This means for every second of video recording, 15 MB of memory will be used. The card we choose to use with the Canon T8i will need to have a write speed of at least 15 MB/s. If the card does not have that write speed, the video will not be recorded properly and we will have useless footage.
There are several indicators of write speeds on SD cards and we will go over each one.
UHS Rating
UHS (Ultra High Speed) Rating defines bus-interface speeds. The interface is the gold-plated electrical contacts on the back of the SD card. These contacts connect the memory card to the camera to read and write information. On the SD card, they are indicated by a Roman Numeral or the word “Express”:
- I for speeds up to 104MB/s
- II for speeds up to 312MB/s
- III for speeds up to 624MB/s
- Express for speeds up to 3940MB/s
Speed Class
Speed Class will let you know the write speed for the card. The numbers are shown surrounded by the letter C. Here are the numbers and their meaning:
- 2 = 2MB/s
- 4 = 4MB/s
- 6 = 6MB/s
- 10 = 10 MB/s
UHS Speed Class
UHS Speed Class also indicates the write speed for the memory card. The numbers are shown inside the letter U:
- 1 = 10MB/s
- 3 = 30MB/s
Video Speed Class
Video Speed Class indicates writes speed for the memory card for videos that measures up to 90MB/s. These ratings are V ratings and the speeds are as follows:
- V6 = 6MB/s
- V10 = 10MB/s
- V30 = 30MB/s
- V60 = 60MB/s
- V90 = 90MB/s
For most prosumer cameras, a 64 GB U3 (or V30) UHS-I SDXC should work well for beginners. Once again, check your camera manual to see which SD cards are compatible with your camera and decide how much memory you need for a specific production.
- 7.2.1: Formatting the SD (Memory) Card
- Here we will go over the importance of formatting the memory card and how to execute it on a video camera.