Apple iPad Camera Connection Kit – What’s faster USB or SD Card?

I’ve just bought a Sony DSC RX100 camera with an Apple iPad Camera Connection Kit. The kit contains an USB adapter and a SD Card adapter. I intend to copy photos to my iPad for review and backup purposes during my holidays. My son argued that the SD card adapter must be faster since the SD Card has a read/write capability of 45 MB/s and the USB 2.0 connection is limited to 35 MB/s. – Sounds reasonable, but nonetheless I had to test that…

… so I shot 300 photos with a total size of 2’155’522’108 bytes. Here are the result of some copy scenarios.

#Copy ScenarioTime in secondsTransfer rate in MB/s
1Copy photos from MacBook Retina card reader to a Mac OS folder using cp47.743.1
2Copy photos from RX100 camera connected via USB adapter to a Mac OS folder using cp211.79.7
3Copy photos from SD card adapter to my iPad 3 using Photos app221.19.3
4Copy photos from RX100 camera connected via USB adapter to my iPad 3 using Photos app279.87.3

My son was correct, the SD card adapter delivers better throughput results than the USB adapter. Further investigation is required to figure out why the transfer rates are far below the theoretical maximums. However, for me both options are good enough and the transfer rates are acceptable.

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