Never Shoot Without Dual Card Slots

Never Shoot Without Dual Card Slots

In the past few weeks, Nikon and Canon have released their new mirrorless offerings, the Z7 and R, to much fanfare. Despite the great specs and form factor, I won't buy either for one simple reason: neither one has dual card slots. I never shoot anything without dual card slots, and neither should you.

When shooting for clients, shooting for myself, or just casually taking a few pictures of my kids, I always shoot with two camera card slots. I am fanatic about not losing any files, be it for clients or just myself. If it is worth shooting, it is worth protecting those files.

In the time between starting this article and finishing it, I had two photoshoots. In the second one, a compact flash card actually corrupted and was not recoverable. I tried several different software solutions, but all of them failed to recover the images on the card. 

Screenshot of Image Rescue Software for memory card recovery

Image Rescue was unable to recover my corrupted memory card

Even though that card corrupted during the shoot, I didn't lose a single file because I shot everything to two memory cards. I wouldn't have even tried to recover the files if I was not in the middle of writing this article because every image was safely on my other card. 

My clients pay me to deliver, and I sure couldn't ask them to redo a wedding because the kiss didn't save to my memory card correctly. 

Constant improvement by card manufacturers have led to fewer card failures, but they still happen. I'm not exactly smart enough to explain how flash cards work or what makes them fail, but I do know someone who is smart enough to understand them. Jeff Wischkaemper is a research professor in the Department of Electrical and Computer Engineering at Texas A&M University. Dr. Wischkaemper also happens to be a talented amateur photographer, so he understands the importance of memory cards to photographers.

"We used CF cards in an industrial product for over a decade. This was not a photographic application, but the primary function of the of the cards was to store files of similar size and composition to images. The CF cards were, without question, the weakest part of the system. Virtually all cards experienced some data corruption after years of use - many of them experienced complete corruption of the entire card, to the extent that no data could be read or written," Dr. Wischkaemper said.

I am all about minimizing risk and there are several ways you can do that. You can minimize risk by buying good memory cards from authorized retailers. I have less failures in my Lexars and Sandisks bought from an authorized retailer such as B&H than I have had with other brands bought in other places. I don't even want to know how many counterfeit memory cards I have used over the years because I didn't buy exclusively from authorized retailers. 

Another way you can minimize risk is changing out memory cards before they fail. As Dr. Wischkaemper said, eventually they all cards he used suffered some corruption or data loss. Replace the cards before they corrupt. Sell them or keep them as emergency backup. You can also do what I do and have a bowl of old cards on a shelf for no particular reason other than I might one day use that 1GIG 80x card from 2005.

In addition to both those ways, you should always shoot dual card slots. I only use new cards purchased from authorized retailers and I change them out regularly. But cards can still corrupt at any given moment, so every time I take a picture, it is written to card slot A and card slot B.

I choose to use raw to card A and JPEG card slot B for a couple reasons, but the main reason is when I shot Canon, I noticed that sometimes the raw file would corrupt when I was hitting the buffer, which was often on the horrible buffer and slow write speeds of the 5D Mark III. But while the raw file would be corrupted, the JPEG file on the other card slot would be unaffected and could be edited normally.

More likely than a card corruption problem, though, is human error. I've heard countless stories of camera bags being stolen, memory cards falling out of pockets, or photographers thinking they backed up the card, then shooting over it without getting all the files.

A lot of photographers suggest using smaller cards and changing them out more frequently. Delkin recently announced three new XQD cards and the smallest size was 64GB. At the time of writing this, B&H didn't offer any XQD memory cards smaller than the Sony 32GB. XQD is the only card format in the new Nikon Z7.

I actually think shooting with smaller cards and switching them out will make you more prone to lose images, because I think the more likely event is human error than card corruption. 

Large cards are all I use — large enough where I do not need to switch out cards during a shoot. I know cards aren't going to fall out of my camera and because I use two cards, I know that me losing my cards is much more likely than both cards being corrupted and unable to recover any files. My cards are only formatted at home, placed in my camera, and only come out when it is time to ingest. Never will I format a card during a shoot.

When you have formatted cards for years, it becomes a habit you can do without thinking and so if you never format during a shoot, you will never format the wrong card out of habit. After a shoot, my used primary cards go into a Think Tank Pixel Pocket Rocket and that stays tethered to me. My secondary cards stay in the cameras. If someone steals all my gear after a shoot, I still have the primary images.

I am really excited to see what my friends, colleagues, and sworn enemies do with these new Nikon and Canon mirrorless cameras. With the great EVF and cool new features, I think we are going to see a lot of great stuff that had not been done with DSLRs. But you won't see it from me. I won't take the risk. I may fall behind the times on this new technology but the risk of losing irreplaceable images for a client is going to be substantially lower.

For years, photographers shot single images on single frames of film. If you ruined the film by not properly rewinding it or in the development process, it was gone and there was nothing you could do. Luckily, times have changed and technology has advanced.

I'll bet you Robert Capa wishes he had a second copy of all the images he shot as he landed with Company E on Omaha Beach for the first wave of attacks on D-Day. Of 106 frames Capa took on D-Day, only 8 were salvaged after the darkroom assistant turned on too much heat while drying the film.

If I lost 94% of my clients files from a wedding or portrait shoot, I doubt they would be comforted much to know that Robert Capa's film was melted almost 75 years ago so no big deal. It happens, right? It doesn't have to happen. We have the technology to do better and our clients deserve better than for us to risk their files with one card slot when there is an option for two.

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Previous comments
Matei Horvath's picture

Thomas, great article. I know you're gonna get a lot of bull from a bunch of 'Uncle Bobs' but hey. I have a ccorrupted XQD card (64GB Sony by the way) ON MY DESK, to remind me to always use a backup card. I always do, shoot Nikon. I have actually turned down second shooters who had cameras with just one card. To anyone who's gonna argue my point, you really don't have to do this at all. I'm really not telling you guys what and how to do your job. This is simply how I DO IT.
Hardware breaks. I've had at least a dozen cards corrupt in different stages of shooting, saving, etc with some images that were lost forever. I'm actually better at taking pictures than apologizing. Will have to wait for the next gen.Just my 2c

Mr Hogwallop's picture

Does Sony actually make their XQD cards? Or are they relabled third party cards?
I would stick to cards made by card/memory makers and cameras and lenses made by camera and lens makers...but that's me.
I retire cards regularly and put the old ones aside for emergencies, I am surprised that you have had so many cards fail but I don't know how / what you shoot.

Ian Goss's picture

I am continually amazed by arrogant writers on this site insisting that readers DO SOMETHING!

I have a Sony, a Panasonic, and an Olympus digital camera—all of ’em have a single memory slot.

I believe in quality over quantity. People spend all this money on their cameras, then go and spend pocket change on the cards. Having two cards slots is great, only if both cards are reliable. One key thing I stay away from is any card that requires a microsd adapters. I've had times where I thought I lost a day worth of photos, only to find out the adapter went bad. Keep in mind this was samsung branded! I learned my lesson with that!

Great article OP. If someone can afford dual card slots, it's definitely the way to go. Better safe than sorry! But starting with quality cards should be a no-brainer!

RIP all the lost files

Tom Robbrecht's picture

I've been shotting digital for the past 15 years, of which a number of years professionally and I've never lost a single image due to data corruption or a bed card. Perhaps I'm lucky.

Coulda sworn write speed decreases when writing to two separate card slots.....

Thomas Campbell's picture

You are absolutely correct. Some cameras (looking at you Cannot 5D Mark III) are very seriously hampered by it.

John Dynia's picture

I shot film, I always had 2 bodies with me. Now with digital its the same, 2 bodies, two flashes. I carry back up cards as well, just like in the old days when I carried more film than I needed. But nothing is perfect. I once worked in a lab and the power went out and we had to crank the film out by hand. The unforeseen can always happen, that's life. You reduce the risks as much as you can but you cannot eliminate them entirely.

To me, with so many pro cameras offering dual slots, I think there *could* be some E&O exposure if you used one slot and your card corrupted. For my own work or nickel-and-dime client work, I would chance one card, but certainly not for anything more significant.

Just stopping by for the comments ;)

Michael Dougherty's picture

Yikes, I've shot hundreds of thousands of images since 2004 and never thought to use a dual card slot. I did have a card failure one time but I simply used a rescue disk program to retrieve the images. On any trip I will unload my memory cards onto my computer and SSD drive every night. I also never delete images in camera and always format the memory card after placing it back into the camera.

Must look up my old Hasselblads and Nikons and check they still have dual film slots.... I mean, we never ever winged it back in the day using cameras with just ONE roll of film in it...
I those days you actually earned 5 and 6 figure sums... for one shoot... shot it on film, then gave the film to someone else..... to develop...! (Admittedly we developed odd rolls then even rolls... just in case.)

Yet we all survived, the ads were great, no one died.....

Instead of using 'twin card slots' as the Northrups and the articles author says..

Why not just reduce your risk and shoot on several different smaller sized cards, just like with film...

Then if you lose a card (2GB,4GB) you haven't lost the whole day.

My first digital camera was an Excellent Fuji S2 DSLR, a 1GB micro drive card was $99 (on sale) that was probably 2002/3 In that time, 15 yrs or so I've only lost one card, a micro drive, as it was in my pocket when we went into the sea.!

Since then not one CF or SD card has failed.

I don't buy cheap cards,
I don't buy dodgy looking fakes
I buy only one brand of card (v well known)
I carry them in proper card cases
I rotate them regularly
I use a good quality card reader

Just simple steps to keep things working


Spend less on gear, more on travel

Niels Veeneman's picture

Thats nice now i need a new camera with two card slots #OMG

John Skinner's picture

2001 Nikon D1 professional body -- one slot.
Nikon entire D2 lineup of professional bodies -- ONE SLOT
It wasn't until the D3 that the two were offered up.

I've shot well over 1 million images on those D1 and D2 series cameras, and truth be told, I can't ever remember loosing ONE image on 4 of those bodies. So the one card slot thing is getting old now. If not for the fact that crappy pro-sumer models have stated adding two slots for people insisting on making movies (of all things) on DSLR bodies instead of using an actual video model, who knows where we'd be.

If you're having memory failure at these rates, I'd suggest rethinking your entire workflow and buying habits. The numbers <> failures just don't support all of this hype. My only beef here is, these body makers can't start charging over 3K with such limited feature sets. It's frankly insulting the general public should see value for the money here.

Mr Hogwallop's picture

...and the guy up the page a bit has had a dozen cards fail. I had a couple fail in the early 2000s but they were Lexar, and really spendy! Since then the tech has improved so it would be safe to use lexar again but why change?
I have lost a few cards, physically misplaced them. Usually they showed up but a few were gone forever.

Are you trolling us? Because this is how you troll us.

Juan carlos Chu Zhang's picture

reason the card failed : you used a lexar card

try high end sd cards smh

Emmet Adriaans's picture

Dear Fstoppers,

If you are going to publish an article like this please designate this as "Opinion: Never Shoot Without Dual Card Slots"

Thank you,


Franklin Knox's picture

This brings to mind my wedding photography days. I carried 4 Rolleiflex cameras. I shot every important photo on 2 cameras and alter shots on all 4.

16mm Camera's picture

Don't do X because of Y...engage.

Jaran Gaarder Heggen's picture

If people are so afraid of losing images because of card errors... WHY THE H do they not set up an onsite live WIFI backup where image files get copied directly to a WIFI enabled NAS...
and if they are so conserned about safety, the single point of failure is still the camera...