Memory cards have their speed rating systems. For example, class 6 is the recommended base class for 1080p HD video coming from DSLRs. Those classes however, don’t tell you what is the burst rate on individual shots. Mostly because each image has a different MB size to it depending on many factors.
Jaroslav over at Crazy Lab found an interesting way of measuring the burst rate and comparing different factors that affect the camera to card writing speed. TO make the test constant he covered the lens of his Canon T3i and took pictures of darkness. By recording the shutter sound (or music as some call it) and displaying the waveform in Audacity Jaroslav was able to compare burst-rates of different ISOs, capturing modes and cards.
There are three tests performed Each test has an initial part where the burst rate is almost identical until the camera’s internal buffer gets filled. Then an image is taken only when the buffer has enough space after dumping data to the memory card.
Here are some of Jaroslav’s interesting findings:
Higher ISOs create bigger. This means that the buffer is filled faster (less images) and it takes longer for each image to clear the buffer.
Raw files are bigger, but for some reason, the camera can take faster RAWs, than JPGs (I am not sure if this has to do with the memory card, though).
[stopwatch by julianlimjl]