To PopPhoto Flash:
I am looking at buying a Canon Powershot G9. I’ll need a big memory card but the SDHC
cards seem slower than the high-speed SD cards.
How do you determine what speed is needed if you want the camera to have the
shortest possible time between shots? What specs should I look for and how is it interpreted if it is not obvious?
To give you a helpful answer, I will need to cover a few aspects of the camera since your question really touches on a few different points that are loosely connected.
As you know, the Canon Powershot G9 is a 12.9-megapixel camera that produces large JPEG files, and can take both SD and SDHC cards. SD (Secure Digital) cards and SDHC (Secure Digital High Capacity) cards work the same way, the difference is, as the name implies, SDHC cards have a higher capacity and are 2GB or larger.
Other than the size of the card, you also want to consider the write speed (the time it takes the camera to write the file information from your picture to the card). Memory card write speeds are grouped by class: Class 2, Class 4, Class 6, etc., each writing the relative megabytes per second to the card, i.e. Class 2 writes 2MB per second, Class 4 writes 4MB per second and so on. SDHC cards used to be slower than SD cards, but technology has caught up and there isn’t that much difference now. Of course, if you’re shooting in RAW, write time is anywhere from 1 to 3 seconds per file, and if you’re shooting in RAW+JPEG, write time is going to be even slower. I would recommend a brand with a track record, either a SanDisk, Lexar or the newcomer Kingston. Since you are concerned about speed due to the file sizes, you should get a 2GB SDHC card, Class 2 or higher (which will cost about $40-$50).