Why does memory card write speed create a bottleneck in burst shooting?
When you hold down the shutter for burst shooting, images fill the camera’s internal buffer (temporary RAM) at high speed. The buffer then writes images to the memory card. If the card writes slower than the buffer fills, the buffer overflows and the camera slows down or stops shooting until the buffer clears — you miss the decisive moment.
How the buffer and card work together
The camera captures images at full speed into a fast internal buffer — typically holding 30-100+ images depending on the camera.
Simultaneously, the camera writes from the buffer to the memory card. The card’s write speed determines how fast images leave the buffer.
If you shoot 20 frames per second and each RAW file is 50MB, the camera needs to write 1,000 MB per second to keep up. No SD card can sustain this. Even fast CFexpress cards can only maintain 400-700 MB/s sustained write.
Result: the buffer fills faster than it empties. Eventually the camera slows to the card’s write speed — maybe 5-8 fps instead of 20 fps.
Card speeds that matter
SD UHS-I (up to 104 MB/s): Fine for casual photography. Buffer clears slowly. Long waits between bursts.
SD UHS-II (up to 300 MB/s): Good for enthusiast shooting. Most cameras work well with V90 UHS-II cards for photo bursts and 4K video.
CFexpress Type B (up to 1,700 MB/s): Professional standard. Buffer clears almost instantly. Used in flagship cameras for maximum burst depth.
CFexpress Type A (up to 800 MB/s): Sony’s compact format. Fast enough for professional work in a smaller card.
Fast memory cards at Camera Shop Egypt
How to minimize the bottleneck
Buy the fastest card your camera supports: The card is the cheapest upgrade that directly improves shooting speed. A V90 SD or CFexpress card transforms burst performance.
Shoot compressed RAW: Compressed or lossy RAW files are 30-50% smaller than uncompressed RAW with minimal quality difference. Smaller files = more images in the buffer and faster write times.
Clear the buffer between bursts: Wait for the card activity light to stop before starting a new burst. Shooting into a full buffer produces erratic frame rates.
Use JPEG for extreme burst situations: Sports photographers sometimes switch to JPEG for maximum burst depth when every frame matters more than RAW editing flexibility.
Check your camera’s buffer depth specification for both the card type and file format you use. A camera rated at 110 RAW frames with CFexpress may only hold 40 RAW frames with a UHS-I SD card. The card makes that much difference.
