Nikon Z7 & Z6 Single Card Misunderstood

If you have read about new Z7 and Z6 mirrorless cameras from Nikon, you will most likely have also read about all the controversy around the card slots. Many people complaining about Nikon’s choice to only supply a single card slot, instead of a dual card slot system, into their two new cameras.

This has stirred up a lot of anger among the comments and animosity towards the new cameras. Most of this is because many are simply not quite grasping the technical details behind Nikon’s decision. Once understood it will become more clear and the value of their choice, will become more appreciated.

As I have already written a tech spec comparison between the Nikon Z7 vs Sony A7R III, I am going to use them as the example case here, although the same applies to the Nikon Z6 as well.

Let’s get right into it shall we.

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Well no, not actually.

XQD Cards are physically larger than SD Cards in height, width and more importantly depth(thickness).

I’ve read a lot of online comments saying: “If my Nikon D500 can have dual card slots then there is no reason the Nikon Z7 can’t either”

They are however forgetting one important fact. The new Nikon mirrorless cameras are much smaller than their DSLR counterparts, which means that space is a high commodity.

For example, the Nikon Z7 is 55.9 cubic inches in size, whereas the Nikon D500 is 85.37 cubic inches. That makes the Z7 34.5% smaller than the D500, while still fitting in all the button, chipboards, sensors, processors and stabilization technology within the camera, as well as making space for storage. When you have a 1/3 less space than before, this isn’t as easy as you might think.

Looking at the comparison pictures below, you can quickly see just how much smaller the Nikon Z7 is compared to the Nikon D500.

Another important factor that many forget, is that a XQD card is slightly larger than SD, so even more space is required from the already smaller camera body, to make room for Dual XQD Cards than it would be for Dual SD Cards. This is why the Sony Mirrorless Cameras are able to offer Dual Card Slots and the Nikon Mirrorless cameras are not.

Then you might be thinking “Well, why not leave the single XQD altogether and use Dual SD like Sony?”

And yes, that was most likely an option and a choice Nikon had to make. They chose XQD.

Also note that dual SD cards in the Sony cameras come with a big sacrifice in speeds, because of how Redundancy Mode works with dual cards.

Redundancy Mode is when a photo is taken, it gets sent and saved to both memory cards instead of just one. This serves as a backup of your images or video, in case one card should fail while out on location shooting.

However, the catch is that when both cards are being used in Redundancy Mode, they both perform as fast as the slowest of the two cards. This means that the XQD Card would only perform as fast as the SD Card.

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So for every ONE SECOND of burst shooting you do with the Nikon Z7, the buffer and memory card have to deal with 765MB of data.

Yes, that means that if you didn’t have a buffer, the memory card would need to run at a speed of 765MB/s in order to compute those 9 images.

As memory cards aren’t that fast yet, our cameras come with a buffer to help them.

A buffer is a short term storage on your camera.

Exactly like RAM on your computer.

It’s there to temporarily store the images while they are written to the memory card (which in computer terms, is the the hard drive of your camera).

Just like your computer, when your RAM is full, your computer comes to a halt until it clears out what it needs to.

In terms of our cameras, once the buffer is cleared and image are written to the memory cards, we can shoot again.

I cover this in more detail in my ProGrade SD Card review, as I compare it to both CFast, XQD and the upcoming CFexpress card speeds

Going back to the XQD speeds on the Nikon Z7 needing 765MB/s for burst shooting without a frame buffer.

If you have a 400MB/s memory card at your disposal, the camera can then deal with that in less than 2 seconds, before its ready to fire again. (765 / 400 = 1.91seconds to be exact)

Can the Sony a7R III do that? I don’t think so.

In fact it takes much longer to clear the buffer especially when dual card mode is enabled.

Why, because it too is limited to its slowest card which in the Sony a7R III’s case is actually a much slower UHS-I card that only writes at a mere 95MB/s.

That means that for the Sony a7R III to clear its 765MB of data, it requires close on 8 seconds to do so. (765 / 95 = 8 seconds).

Now, can you see the value in a single card slot, but a very powerful one?

I certainly can.

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At the same time I’m not saying single is better than dual, they serve different purposes and thus different needs of photographers.

Unfortunately, we cannot have both speed, dual and a small form factor camera body at this stage in time. As technology progresses (as it does), sure, we could see something as small as Micro SD card pumping out double that of a current XQD card speeds in the next few years.

But not right now.

So you have to decide here. Do you want burst speed or do you want the security that you have a backup of your day’s images and videos?

That really depends on you and your nature/industry of shooting.

Many wedding photographers live by the safety factor, which is very understandable. When a bride is paying you that much money to shoot the most important day of her life, you best make sure you have a backup of everything in case something fails. Wedding photographers also don’t need the speed of XQD cards. So for you, dual SD cards are more important than one XQD card. Rather go with the Sony a7R III, Sony a9 or Sony a7 III in that case.

Same for landscape photographers. You are in no rush either and hiking out for 4 days to get that perfect shot, only for your memory card to fail is a killer. It’s thankfully never happened to me personally, but has clearly happened to others before.

Here again, dual cards are my recommendation. Go with any of the Sony cameras.

For a professional wildlife or sports photographer who needs the fastest write speeds and lowest buffer clear times that they can get, the Nikon Z7 by far the better choice compared to the Sony a7R III, thanks to its ultra fast XQD memory card.

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Let’s spice things up and include the Sony a9 in this equation,

The Nikon is able to shoot 45.4MP image at 9fps with a 2sec buffer clear, whereas the Sony is only able to achieve its 20fps because its shooting 24MP and because of its Stacked Sensor which is required to achieve this feat.  The a9 also costs more because of this extra sensor.

And even then, the stacked sensor does nothing to help clear the buffer which can take up to 110sec when in dual card mode.

Currently the Sony a9 shoots:
24MP images that are 48MB in size with a maximum write speed of 95MB/s. This means that (95 ÷ 48 = 1.97) images are written per second.

Currently the Nikon Z7 shoots:
45.4MP images that are 85MB in size at 400MB/s. This means that (400 ÷ 85 = 4.7) images are written per second.

Remember, the Nikon Z7 shoots 43% higher resolution at 9fps without a stacked sensor, so let’s shift some numbers to compare them evenly:

First, let us make them the same MP and thus file size.

As we are reviewing the Nikon Z7, let’s bring the a9 up to its file sizes.

Thus, if the Sony a9 were to shoot 45.4MP images that are 85MB in size at 95MB/s, then only (95 ÷ 85 = 1.12) images are written per second.

Nikon Z7 = 4.7 images per second
Sony a9 = 1.12 images per second

Thanks to just the XQD card in the Nikon Z7, without any form of Stacked Sensor, is able to outperform the Sony a9 by 4.2 times in buffer to memory speeds.

So while the a9 is sitting there clearing its buffer, the Nikon is ready to knock out another round. This is why the Sony a9 has such a big 225 image buffer and the Nikon only has a 23 image buffer. Simply because the Nikon Z7’s write speeds are so fast, it will hardly ever need anything bigger.

That is truly amazing.

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Hopefully you guys understand the decision by Nikon.

I for one think it was a good one.

We already have dual slots from Sony but we don’t have a Full Frame mirrorless with the speeds of XQD. This opens up doors for us as consumers, to choose which we want and not just have the same in every camera. XQD also uses the same platform as the upcoming Cfexpress cards, meaning that once CFexpress card become available, such as those by ProGrade, Nikon just need to implement a firmware update to allow you to use CFexpress instead of XQD, giving you a whopping 1000MB/s write speeds. You can find more info on this in my ProGrade SD Card Review

Of course you don’t have to use dual card slots on the Sony cameras, which will give you 300MB/s if you buy the Sony SD Cards, but that defeats the purpose of dual vs single slots altogether. However, the benefit is that with the Sony cameras, you have the option to go with one 300MB/s Card or dual 95MB/s cards, whereas with Nikon, you can only choose 400MB/s.

Again a trade off wither may. Either a 100MB/s (25%) increase in single card write speeds or a 95MB/s (1/4) card write speeds in dual card mode.

A nice solution would be to include an additional XQD or SD Card in battery grip for the Nikon Z6 and Z7 cameras. Whether that is even technically possible, im unsure. But if it is, It could be a great solution for many photographers that want to use the Nikon mirrorless cameras, but also want dual card slots.

This also means that you would also get the best of both worlds:

The speed of XQD and the security of dual cards, thereby opening up the cameras to all genres of photography and photographers.

Please leave your thoughts in the comments but be respectful.

If the dual card slots of the Sony cameras are what you need, you are welcome to also check out my other comparisons

Sony a7 III vs Sony a9
Sony a7 III vs Sony a7R III

As you are a dual card slot photographer, you will most likely be shooting weddings. If so make sure to not miss the the new Sigma range of prime lenses for Sony E-Mount

Also check out the soon to be released Atomos Ninja V which pushes your videography to the next level by not only offering a better screen that can be used as a selfie/vlogging screen, but and makes the Nikon Z7 & Z6 cameras true 10-bit HDR capable. If you are interested in HDR, then you need to learn more about ProRes as well