Write Speed vs Read Speed for Burst Photography

How does the camera buffer capacity influence the necessity of high write speeds?

The camera buffer acts as a temporary holding area for image data before it is written to the memory card. If your buffer is large, like the 100-plus RAW file capacity found in high-end sports cameras such as the Nikon Z9, you can sustain long bursts even if the card is relatively slow. The camera simply dumps data into the RAM until the buffer fills up. Once that limit is reached, the camera’s burst rate drops to the speed at which the card can clear the buffer.

However, if you shoot with a compact camera that has a shallow buffer, you hit that performance wall almost immediately. In these cases, a high-speed card is the only way to maintain a steady frame rate. The nuance here is that high-resolution sensors generate massive files that fill buffers faster, making high write speeds mandatory regardless of initial buffer size.

What is the difference between sequential write speed and sustained write speed in the context of continuous shooting?

Sequential write speed represents the peak burst capability, while sustained write speed is the minimum speed a card maintains during prolonged recording.

Look for cards that guarantee a high sustained write speed to avoid stuttering during long sequences.

Does a faster memory card allow for a longer burst duration before the camera slows down?

Yes, a faster card allows the camera to clear the buffer more quickly, extending the burst duration. For example, upgrading from a 90MB/s card to a 250MB/s card can double the number of frames captured before the camera’s internal frame rate begins to throttle.

How do file formats like RAW versus JPEG affect the required data transfer rates during high-speed photography?

RAW files contain significantly more data than JPEGs, requiring much higher transfer rates to prevent the buffer from filling during rapid shutter actuations.

Match your card's write speed to the file size of your chosen format to keep the buffer clear.

What role does the camera's internal processor play in determining the bottleneck for burst performance?

The internal processor manages the translation of raw sensor data into image files, often acting as the primary bottleneck before data even reaches the memory card.

• 10 frames per second: At this speed, the processor must encode and move massive amounts of data in milliseconds, often limiting the burst duration regardless of card speed.
• Image resolution: Higher megapixel counts increase the processing load, forcing the camera to compress more data per shot.
• Bit depth: Shooting in 14-bit rather than 12-bit increases the file size, which forces the processor to work harder to move data through the internal bus.
• Noise reduction: Applying heavy in-camera processing tasks slows down the throughput to the card.

Are there specific memory card standards, such as V60 or V90, that are optimized for high-frame-rate burst shooting?

Yes, the V90 rating is specifically designed for high-frame-rate recording, guaranteeing a minimum sustained write speed of 90MB/s. This standard is necessary for cameras shooting 4K video or high-speed continuous bursts, as it prevents the camera from hanging when the buffer fills up during intense action.

How does the speed of the memory card interface, such as UHS-II or CFexpress, impact the clearing time of the camera buffer?

UHS-II and CFexpress interfaces use additional pins or lanes to increase the throughput between the camera and the card, significantly reducing the time it takes to empty a full buffer. Many people assume that a faster interface will increase the camera's maximum burst frame rate, but it only affects how quickly the camera recovers once the buffer is full. If your camera is limited by its internal bus, even the fastest CFexpress card will perform no better than a standard UHS-II card.

Is there a point of diminishing returns where increasing memory card speed no longer improves burst shooting performance?

Performance plateaus occur once the card's write speed exceeds the maximum throughput capacity of the camera’s internal controller.

• 250 MB/s: Most modern professional cameras reach their internal throughput limit at this range, making faster cards redundant for burst shooting.
• Camera bus: The physical hardware inside the camera dictates the maximum speed, and once the card exceeds this, no further gains are possible.
• Heat management: Extremely high-speed cards generate heat that can trigger thermal throttling in the camera, potentially slowing down performance during long sessions.
• Diminishing returns: Spending extra on top-tier cards offers no benefit if the camera cannot physically write data any faster than its current ceiling.