Restore SD Card Speed

SD Card Maintenance:

Restore SD Card Speed with a Full Format

If you’ve noticed your SD cards slowing down and buffering—especially when shooting in burst mode or transferring large files—it might be time to give them a little maintenance. Even high-speed cards can start lagging after heavy use, but there’s a simple fix that can bring them back to life: a full format.

Quick Format vs. Full Format

Most photographers know to quick format their cards in-camera before every shoot. This clears the file table, which tells the camera where data is stored. However, it doesn’t actually erase the data—the old blocks remain in use. Over time, this build-up can seriously slow down your card’s read/write performance.

Real-World Example: Sony A7RIV with 300MB/s Cards

I run 300MB/s SD cards in my Sony A7RIV. Lately, some of my older cards started showing heavy buffering during burst shooting—especially with 123MB RAW files. I ran speed tests and saw significant slowdowns:

Before Full Format:

• Newest card
  • Sequential Read: 287MB/s
  • Write: 144MB/s
  • Random Read: 51MB/s
  • Write: 3.1MB/s
• Slow card
  • Sequential Read: 88MB/s
  • Write: 70MB/s
  • Random Read: 12MB/s
  • Write: 1.9MB/s

After Full Format:

• Slow card 1
  • Sequential Read: 208MB/s
  • Write: 154MB/s
  • Random Read: 31MB/s
  • Write: 3.0MB/s
• Slow card 2
  • Sequential Read: 271MB/s
  • Write: 152MB/s
  • Random Read: 36MB/s
  • Write: 3.2MB/s

The Result?

Massive improvement. Burst shooting is now buffer-free, and the cards feel like new again. These cards are 2–3 years old with countless writes, but after a full format, they’re still performing at 200–270MB/s. While I’ll replace them soon, they’ve got plenty of life left.

How to Check Your Card’s Speed

You can test your SD card’s performance with disk speed utilities:

• Mac: DiskMark
• Windows: Tools like CrystalDiskMark or ATTO Disk Benchmark are popular alternatives.

Your card’s label should list its top sequential speed—usually 170MB/s, 280MB/s, or 300MB/s. Use those numbers as a benchmark during your tests.

Final Tip:

Do a full format every few months (using your computer, not just in-camera) to keep your SD cards performing at their best—especially if you’re doing high-volume shooting like weddings, sports, or time-lapses.