Do You Need Two Card Slots in Your Camera?

If you are new to photography, you have probably noticed professionals talking about the need for dual card slots a lot, sometimes so much so that they will refuse to buy a camera that only has a single card slot. Why is that so important? Do you really need two card slots? This excellent video features an experienced photographer discussing some of the reasons photographers use two card slots and how they can benefit you. 

Coming to you from David Bergman with Adorama TV, this helpful video discusses the issue of dual card slots. While there are multiple advantages to using two card slots in a single camera, the main reason most photographers advocate for it is to protect data in case one card fails. In fairness, modern memory cards are a lot more reliable than those from a decade or two ago, and you can probably safely shoot with a single card slot most of the time. Nonetheless, no card is completely failsafe, and if you are shooting something where you won't get a second chance, such as a wedding, a second card slot is never a bad idea. Check out the video above for the full rundown from Bergman. 

Alex Cooke's picture

Alex Cooke is a Cleveland-based portrait, events, and landscape photographer. He holds an M.S. in Applied Mathematics and a doctorate in Music Composition. He is also an avid equestrian.

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Yes. I've had one card failure, but it was in a 5DIII and the CF card was fine. It is good insurance against an unthinkable result for a professional, especially those that shoot one off events like weddings. I don't shoot paid stuff anymore, but I still want two slots. I made a once in a lifetime trip to Churchill, Manitoba to photograph the polar bears. I can't imagine what it would have been like had I had a camera with one slot and that card failed.

As Dave says, for weddings: yes, you do need to use both card slots.

Had a card fail on me during a wedding last year. Wouldn't be without 2 slots and I'm glad I wasn't that day

In the last 10 years, I've never had a card fail. However, I once accidentally formatted a card when I meant to just run the in-camera sensor cleaner. It was muscle memory since 98% of the time, I only enter the menu to format and sync dates/time with my two bodies. This was on a Euro trip and I lost all my Venice images. I did put the card away and when I got back home, tried 3 different file recovery tools and none could recover any images.

Nowadays, with one of my bodies having dual slots, I use both slots to record simultaneously just to be on the safe side. I feel better knowing I have a in-camera backup. I only have to clean out the old files every 4 to 6 months so it's not really a hassle. I can go longer if I'd stop being a frugal bastard and replace the 256 gb with a 512+. :D

Like the new Hasselblad I would prefer if camera manufacturers would start implementing SSD drives (1TB in the HB). This could alleviate the need for a 2nd card slot (and the purchase of a 2nd set of cards).
I have a Nikon Z7 and do events once a year. But anytime I do it I wish I had a 2nd slot.

I usually use a 2nd card for backup, but take it out, when I shoot BIF, because the SD card in the 2nd slot is much slower than the CFExpress in the primary, hence the memory buffer fills up too fast for longer series

Two card slots are only worth it if both are matched. If one is a higher spec than the other you are limited to the slower card slot if you want to backup your files.

That's a misnomer. I used to think that (probably because of the internet). It's not necessarily true. Mine have different speeds and I don't notice a difference. If I were to shoot sports and/or constantly shooting in long hi-speed bursts, then, the slower card may come into play. But, for normal speed or short busts, it's fine.

Also, depends on the speed of the slower card. The slower card I have writes at 86.68 MB/s. My body (a7iii) is 24 MB. Then, there's the buffer. Just as a test, with two cards in, I held down the shutter for 42 frames in normal speed (it never slowed down)...only 10 were in the buffer when I lifted off the shutter and it emptied in less than 2 seconds.

Of course it depends on the speed of the slower card but if you want to take advantage of the higher speed card, that's when it matters. The two slots on my Sony are mismatched SD card slots but for photography it isn't a problem, mainly if you want to shoot 4K video and back it up is it a problem.

--- "if you want to shoot 4K video and back it up is it a problem."

That's actually also not true. I shoot 4k30p 100 MB/s video with two cards and it's fine. I've done a 5 hour wedding and it's fine.

Just curious, have you actually had these issues that you speak of? Or, just something you read/heard on the forums and Youtube that speculated based on the specs?

Yes I’ve had these issues and read a number of comments saying the same. If you can’t take advantage of the higher spec card then what’s the point. If you need a faster buffer speed for example you’ll be restricted to the slower card. Just because you've never had a problem, doesn't mean this issue doesn't exist.

--- "If you can’t take advantage of the higher spec card then what’s the point."

1. I don't understand your convoluted flip-flopping. You apparently find value and purpose in it because you yourself are using both slots, "The two slots on my Sony are mismatched SD card slots but for photography it isn't a problem"

2. Read speed matters. When off on location, having the faster cards does help when copying files. They can be up to 1.5x faster. And, those are the not so expensive ones.

--- "Just because you've never had a problem, doesn't mean this issue doesn't exist."

I'd like to think you know not all cards are the same. If you are having issues, you're most likely using very low spec'd or non-compliant cards. They matter.

Below is a chart of the cards I have. All are UHS-II except the bottom 3. The 3rd from bottom (Samsung) is what I use for backup. Other than the 32 gb cards, they all work for 4K recording.

Maybe I've just been lucky (and maybe one of my cards will fail tomorrow), but I've only had two cameras in my many years of shooting digital (5D Mark IV & Fuji XT-3) that have dual card slots. Other cameras (Canon 30D, 5D Mark II, XPro-1 to name a few) only had one slot and the cards never failed and I've never accidentally formatted anything. I am pretty careful about my backup strategies though. I never go on a shoot without my laptop and external drives (even if I'm not shooting tethered) and always backup the day's shoot as part of my packing up routine. I am smart enough ... and pragmatic enough ... though to realize that card failure on a paid shoot is not an option that you want to allow for, so multiple cards in the camera (just like multiple cameras in your bag) is an absolute minimum to guard against a "just in case" scenario. Honestly ... these days, I worry more about my bag getting jacked on a shoot more than I do my cards failing.

I flat fail to understand the logic in having two different media types on a single camera body. If you're going to do shoot video, use two CFExpress cards; if you're going to shoot stills, use two SDXC cards. My G9 bodies use two SDXC cards, and they're set up to back each other up in case one of my cards dies. I do wish that camera manufacturers would get this concept understood.

With CFExpress B cards it is probably a size issue with dual identical slots. Plus SD cards are mostly cheaper and that could be an incentive for customers. Also if you travel and need more storage you probably will get an SD card more easily than an CFExpress B or A card.
These might be reasons. But Sony uses 2x CFExpress A that also serve as SD Card slots. That is also clever.

Ever notice with articles about dual card slots, the comments are mostly about backup or card failure. The video talks about a number of reasons for two card slots other than backup...

People fixate on "failure." Card failure is possible, but the more likely thing to happen is human error; losing a card, inadvertently formatting, etc.

In the last decade I've had exactly one card fail. But I've also had a card misplaced (found it later) and I've had one that was fumbled when handing it to an assistant and it fell down a storm drain in the street. There was no way of retrieving it. In both instances it was not too distressing because I had my secondary card as a backup.

I see how dual card slots can be a benefit. But I've never had a card fail during any shoot so I doubt I'll use both slots simultaneously. There have been a few occasions where I mismanaged my CFExpress Type B cards (i.e., forgot to dump the card onto my PC before heading out to the next shoot) and ran out of space so I had to improvise and stick in a SD card to continue shooting.

Been shooting weddings etc for over decade, and all I care about, two card slot is not in my mix of things to worry about, I use more than one camera.
If it fails just switch to a spare and move on.
Had card fail, only twice, switched to a new one, and performed recovery when I got home.
Just make sure to get a genuine brand high speed card and you will be fine.
I don't know what the fuss is about.

The problem lies in the fact that some shots are fleeting, lasting maybe 30 seconds. In the time you realize that a card has failed and you make the switch could be the time that Dad was walking the bride up the aisle and you miss it. I know it hasn't happened to you, but do you want to stand in front of the bride, groom, and bride's mother and tell them that you missed that shot?

Yes, it's rare, but if it happens, it's hard to explain away something that you had control over and that you decided it wasn't worth the worry. I mentioned before that I don't do paid stuff anymore, but two slots are still mandatory for me. I mentioned my trip to Churchill above which is something I'll never do again. Had I had one card and it failed, there's no telling how many polar bear shots I would have lost. It's just not worth it. But, it's horses for courses.

"You will be fine" is not at all reassuring. First of all, your "genuine brand" card may turn out to be not so genuine. And as David notes, you may not realize a card has failed until 30 seconds or more have gone by. In that time, you may have lost essential photos. Furthermore, a card can physically fall apart, so that it won't even fit into a card reader for recovery software to work. I've had genuine Sandisk Extreme cards peel apart like junk.
Two slots are mandatory for me for a wedding or anything similar. I shoot RAW to both.

Exactly! There are other reasons for dual card slots besides mitigating card failure.

Saying I've never had a card fail so why do I need two card slots is like saying I've never been in an car accident so why do I need a seatbelt.