by Linus Kleen
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Cameras rarely specify exactly what speed cards you should be using in them - I just checked the manual for my DSLR, and all it says is to use an SDHD card, and a "high speed" card should be used for recording video. On the other hand, there are a number of different rating systems for memory card speed (33x! 150x! Class 2! Class 10!) and price seems increases with speed. Is there any way to test the maximum write speed the camera is capable of? Are the read/write speeds documented anywhere? |
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Camera reviews on dpreview mention writing speeds (example: EOS 550D). If there's no documentation it should be possible to derive actual camera+card write speed by switching to RAW and shooting in sequence until your buffer fills up (then shooting fps should go down significantly). Then writing_speed = raw_file_size * fps_with_full_buffer. |
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For SDHC cards there are "Class" ratings that indicate the speed. There is a table on wikipedia that compares the ratings, but the class # is the key. I have used Class 10, which is fairly affordable, but still quite fast. It will never hurt to have a faster card, so given a choice you always want the higher class. Update: There is a new designation of "Ultra High Speed" (UHS) which have a theoretical limit of 104MB/s and a version two coming (UHS-II) which has a theoretical limit of 312MB/s |
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