Today’s Question: You had recommended setting your camera [the Canon EOS 7D Mark II] to record to two memory cards at the same time. My camera has this feature, but when I capture video it is still only saved to one card. Photos are going to both cards. How do I fix this for video?
Tim’s Quick Answer: You can’t fix this on the 7D Mark II (or as far as I know on any other digital SLR). While photos can be saved to two cards at once thanks to two cards slots on this camera (among others), you can’t save video to two cards at once.
More Detail: While you can’t record video to two cards, you can choose which card the videos get saved to. The result is that your photos will be saved on both cards, but your videos will only be saved on one of those cards.
In general I would tend to use the fastest media card of the two for saving video. However, I actually opt for the SD card rather than the CompactFlash card as the card that my videos get stored to. That is because my primary computer has a built-in SD card reader. In other words, I prioritize convenience in my overall workflow rather than the performance of the card. And, of course, I use relatively fast cards in any event.
In the case of the Canon 7D Mark II you can choose which card to record videos to from the menu on the LCD. Under the “Set Up 1” menu you can choose the “Record fun+card/folder sel.” option. Then, with the “Record func.” option set to “Rec. to Multiple”, choose the Playback setting and choose the card you want to use for playback. That card will then also be used as the card that video is recorded to.