How viable an alternative to a second card slot is an On-the-Go card reader? A camera that writes simultaneously to a second card offers real-world insurance particularly when shooting in challenging one-off contexts. If one card fails the other has already created copies of all the files.
According to some professionals cards fail more often than many of us think. I had a new 32 GB Samsung micro SD card suddenly fail in my Samsung tablet. So it can happen.
Recently I bought the card reader above (£10) and used it to copy my SLR’s 120 image files to my smartphone’s micro SD card. I always shoot RAW + JPEG. The 60 20 MP JPEGs copied across very quickly indeed and each .CR2 RAW file took about 5 or 6 seconds. A fancier phone may do better.
It’s definitely not as convenient as a second in-camera card. I know I’ll have to stop shooting, take out the card, put it in the reader and connect them to my phone or tablet. But it takes just several minutes and it’s good to know all my precious images are safely stored on the phone in my pocket. And of course, in a demanding situation (unlikely for me), another option is to put a second card in the camera while the first is backing up to the phone.