Camera displays 'hot card' warning - this is the solution

To get straight to the point, the issue of the "hot card" error message is typically not caused by a fault in the memory card but by using an older CFX card in, for instance, a Nikon Z9 or Nikon Z8 camera. The solution is simple: use a faster card. But how do you know when a card is fast enough?

Hot card warning

'Hot Card' error caused by insufficient write speed

When selecting a CFexpress card for high-speed cameras like the Nikon Z9 and Z8, it is crucial to look for the right type with a high minimum guaranteed write speed. This applies to other cameras as well, which demand fast write speeds, such as the Canon R5C, Canon R5, Canon R3, Canon C500 Mark II, Canon C300 Mark III, Panasonic GH6, Sony A1, and DJI Ronin 4D. These cameras can also experience overheating issues if the write speeds are not sufficiently high.

"These cameras can also suffer from an overheated card if the speed to write the data away is not high enough."

The minimum guaranteed write speed is more important than the advertised read speed when choosing a CFexpress card for high-speed cameras. Even cards with indicated write speeds of 1300 Mb/s or higher may not always achieve these speeds consistently. Therefore, it is essential to pay close attention to the minimum sustained write speed when purchasing a CFexpress card.

Lexar card
OWC card

New generations of cards

With most cards, you'll notice that the latest generation of CFexpress cards comes with improvements in thermal throttling and minimum sustained write speeds. This is to prevent the card from getting too hot. However, the Nikon Z9, for example, still prefers cards that deliver consistent performance, with a minimum sustained write speed of 1300 Mb/s as an absolute necessity. This is more critical than solely focusing on the top speed due to the camera's limited buffer capacity.

Data transfer for 4K and 8K filming

When recording 8K 120P on the RED V-Raptor, the maximum data speeds can reach up to 850 MB/s. This means you'll need a card that can handle and sustain these speeds for extended periods. The Nikon Z9, when recording 8K 60p N-RAW (High Quality setting), also generates high speeds, up to a maximum of 750 MB/s.

"This means you need a card that can maintain these speeds for a longer period of time."

On the other hand, the Canon R5/R5C only requires a card that can support 400 MB/s for recording 8K RAW. Therefore, it's essential to use certified media for certain cameras, as not every random card can achieve the required data speeds.

Cards with sufficient write speed

For Nikon Z and Canon R cameras, you need a Type-B CFX card, while Sony requires a Type-A card. It is very important to buy the right type of CFX card, as they are not interchangeable. This is because these cards have different dimensions, meaning a CFexpress B card will not fit in a CFexpress A slot.

So don't be distracted by the MB/s speed listed on the card. That is almost always the maximum reading speed.

Lexar card
Angelbird card
OWC memory card

Best CFX Type-B cards for Nikon Z9/Z8 and Canon R5:

  • Lexar CFexpress Type B DIAMOND -The latest version of this card has a sustainded writespeed of 1600Mb/s.
  • Angelbird AV PRO CFEXPRESS B SX - This card has a sustainded writespeed of 1480Mb/s.
  • OWC Atlas Ultra CFX kaarten - These cards have a sustainded writespeed of 1500Mb/s.

Featured: OWC Atlas Ultra CFX cards

The OWC Atlas cards are resistant to use in the harshest conditions, including X-rays, UV, shock, drops and extreme temperatures. In addition, they come with the OWC Innergize™ software for checking the health of the card, resetting to factory settings as well as performing firmware updates of the CFX card.

You can also use the OWC Copy That® software for fast and accurate transfer of recordings to backups. With this software, you can streamline the copy process by making fast and verified copies of files to one or more destinations. OWC has this handy compatibility chart to see which card you need for your camera.

Lexar memory card
Angelbird memory card CFX A

Best CFX Type-A cards for Sony E-mount cameras

So for Sony cameras, you need a CFX Type-A card. The advantage is that this slot also fits a regular SD card. The disadvantage is that the maximum achievable speed of a Type-A card is much lower than that of a Type-B card. Because of the much higher writing speed, it is absolutely recommended to use a CFX card instead of an SD card for High-Speed Continuous shooting and 4K or 8K video.

  • Lexar® Professional CFexpress™ Type A Card GOLD Series of 320GB has a minimum sustained write speed of 700Mb/s.
  • Angelbird AV PRO CFexpress™ 2.0 | Type A of 1TB has a minimum sustained write speed of 650Mb/s.

If you compare these minimum sustained write speeds with the speeds of an SD card, you see that SDHC/SDXC simply falls short in terms of speed. In fact, the writing speed of a CFexpress card is more than twice as much. They are fine cards in themselves, but better opt for the CFexpress Type-A if you use a Nikon Z8, Nikon Z9 or other high-speed camera.

  • Lexar® Professional 2000x SDHC™/SDXC™ UHS-II GOLD Series kaart of 256GB has a minimum constant write speed of 260Mb/s.
  • Angelbird AV PRO SD MK2 V90 (SDXC UHS-II) kaart has a constant write speed of 280Mb/s.

Featured: Angelbird AV PRO CFexpress™ 2.0 Type-A

Designed specifically for use with Sony Alpha and FX cameras, the Angelbird AV PRO CFexpress™ 2.0 Type-A card has a minimum sustained write speed of 650 Mb/s. In addition, this card has the highest available capacity in a single 1TB card. With this card, you can achieve critical speed and performance for capturing long, high-data-rate video recordings, stills and burst photography up to 8K RAW.

Thanks to Angelbird's Stable Stream™ technology, the card supports a consistent and uninterrupted sustained write speed of 650 MB/s across its entire capacity. This feature enables super-fast shooting while maintaining all available features and settings of Sony's CFexpress Type A cameras, such as the Sony α1, Sony α7 IV, Sony α7S III, Sony FX3 and Sony FX6. Moreover, the high-capacity card supports 16-bit shooting, offering a wider range of post-production editing options.

Choose the right CFX card size

If you are in doubt between a 500GB, 650GB card or a 1TB card, it is wiser to go for the 1TB card as it has a slightly higher sustained write speed. For example, the OWC Atlas Ultra CFX B 1TB has a sustained speed of 1500Mb/s and the 650GB version has a sustained speed of 1300Mb/s.

6 other tips to prevent camera overheating

Besides a memory card getting too hot, it is more common for the camera itself to overheat. Because the latest cameras have so much technology built in, as well as generating very large data streams with very ultra-high video resolutions and super-fast burst rates, an overheating notification for the camera occurs sooner than you might expect. So this is separate from the notification that the card is too hot. Fortunately, there are some simple things you can do to prevent or delay your camera overheating for longer:

  1. Place a grip under your camera. This places the warming batteries further away from the camera body/sensor.
  2. Change batteries a bit more often, even if they are not yet empty. This allows you to use a cooler battery for much longer.
  3. Use an external battery power supply or AC adapter with cable to the camera. This gets very little battery heat into the camera.
  4. Swivel the LCD to the side of the camera or if this is not possible pull the screen into a 45gr position. The LCD screen quickly becomes very hot and this prevents heat from entering the camera.
  5. Turn the camera off completely between shots and open the battery compartment.
  6. Put the camera on a tripod instead of clasping it with your hands.

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