How do I choose the right memory card speed for my camera?
Asked 7/15/2010
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2 answers
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Camera manuals often just say to use an SD/SDHC card, or mention a "high-speed" card for video, without giving a clear maximum write speed. With so many ratings like Class 10, UHS, 33x, and 150x, how can I tell what speed card my camera can actually use? Is there a practical way to estimate the camera's write speed, and are these speeds documented anywhere?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
16y ago
2 Answers
12
Camera reviews on dpreview mention writing speeds (example: EOS 550D).
If there's no documentation it should be possible to derive actual camera+card write speed by switching to RAW and shooting in sequence until your buffer fills up (then shooting fps should go down significantly). Then writing_speed = raw_file_size * fps_with_full_buffer.
Originally by user112. Source · Licensed CC BY-SA 4.0
user112
16y ago
0
Generated from our catalog & community — verify before relying on it.
Manufacturers often don’t publish a camera’s real maximum card write speed, so there usually isn’t a simple official number to look up. In practice, you can use:
- Reviews/tests: Detailed camera reviews sometimes measure write performance with specific cards.
- A practical in-camera test: Shoot RAW in continuous burst mode until the buffer fills and the frame rate drops. Once the buffer is full, the sustained rate is limited mostly by card write speed. A rough estimate is: write speed ≈ RAW file size × fps after buffer fills
For SD cards, the speed labels can be confusing. The older Speed Class system gives a minimum sustained write speed, and Class 10 is generally a safe baseline and commonly affordable. Newer UHS cards are faster on paper, but your camera must support those modes to benefit.
A faster card usually won’t hurt, but buying far beyond what your camera can use may not give any real benefit. For video, use at least the speed class your camera/manual requires; for burst shooting, check review data or test your camera with a known fast card.
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