There’s a lot of hub-bub regarding single versus dual card slots in the world of digital photography these days. But other than more storage space, what is purpose of having dual card slots and who would it benefit?
Single Versus Dual Card Slots: Why Have Two?
The most obvious benefit of having dual card slots in your camera instead of having just one is more storage space / longer time between card swaps. But there are other possible options for using two cards instead of just doubling the available storage, such as:
- Card #1 stores still images / Card #2 stores video files
- Card #1 stores RAW / Card #2 stores JPEG
- Cards #1 and #2 store duplicate data (instant backup)
It’s that last one (instant backup) that many photographers are most keen to use. The other two are interesting options, but most people probably wouldn’t make a purchase decision based purely on in-camera file organization.
Some Recent Cameras That Only Have 1 Slot
Both Nikon and Canon recently released their first full-frame mirrorless camera bodies, yet neither the Nikon Z6 or Nikon Z7 nor the Canon EOS R have dual card slots. This is something that has a lot of photography enthusiasts scratching their heads. Cameras in this price range usually have dual card slots.
Photographers Who Benefit from Dual Card Slots
Event / Sports Photographers
If you shoot paid event photography (weddings, corporate events, concerts, sporting events, etc), you will almost certainly require dual card slots. There’s nothing worse than spending hours shooting a one-time event and losing all the images because a corrupt memory card fails and is totally unreadable. Imagine telling a bride and groom that they will have no or very limited photos of their wedding and/or reception. Yikes!
Such an occurrence might also open up a photographer to legal liability at worst, but at the very least it could damage their reputation. Why take the chance? Go for a body that has dual slots, such as the Nikon D750 or Canon 5DMk3.
Frequent travelers who are serious photography enthusiasts may also appreciate the
“bigger storage” configuration of dual card clots. Those traveling as light as possible may not have the option to offload memory cards on a regular basis. So, having maximum capacity while carrying a minimum of cards may be be a big help while on the road.
Photographers Who Are Probably Okay with One Card Slot
If you aren’t getting paid for your photography, you don’t *need* dual card slots (but you might still *want* this option, of course). Or if you have the luxury of a re-shoot in the unlikely event of a card failure, you can probably skip two slots. The more controlled the environment (studio), the less need there is for memory card redundancy and on-the-fly backup (in my opinion…I’m sure some will disagree).
How Often Do Memory Cards Fail?
For name-brand cards, the general consensus is “not very often”. There is a maximum number of write cycles on any given card (this varies by card type and manufacturer) after which it will be come unreadable. But this is usually on the order of 5,000 write cycles, which means the card can be filled up 5,000 times before it should, theoretically, fail. Some manufacturers claim much higher write cycle counts. You will most likely encounter a manufacturing defect or mechanical failure well before a card becomes unreadable from over-use electronically.
Every time a memory card is inserted, there is mechanical contact with the camera. Eventually, these metal contact wear out and will no longer make an electrical contact (and thus become unreadable). Or, the plastic enclosure of the card could become brittle and break off at the edges, rendering the card unable to read by a computer or other interface device.
But the bottom line is that random mid-photo-shoot card failure is not a common thing. It does definitely happen, but it is certainly not a likely occurrence at any given photographic event.
Summary: Single Versus Dual Card Slots
Even though random and catastrophic memory card failure is generally a highly unlikely event, it remains a possibility. If you are planning to enter the world of paid event photography or travel extensively and like to create photographic travelogues, you will definitely want a camera with dual card slots configured for writing each image to both cards (backup mode). Otherwise, you are likely okay with just one card slot, although having two is never a bad thing.