How the Nikon Zf’s Dual Memory Card Slots Actually Work

The Nikon Zf has two memory card slots, and they take two different card formats. Slot 1 is for full-size SD cards and supports the faster UHS-II interface. Slot 2 is for smaller microSD cards and is UHS-I only.

It’s an unusual combination, and I’ve written before about which memory cards to get for the Nikon Zf.

But what I’m focusing on here is the dual aspect of it. And, more specifically, how to control the way in which the camera uses them.

This post could easily be subtitled “Why You Should Use 2 Memory Cards in Your Nikon Zf,” because I’d argue that there are strong arguments in favor of filling both memory cards. But that’s not actually a requirement — the camera will work just fine with only one memory card slot filled. (If you’re choosing only one, the full-size SD is a better option, especially if you’re shooting video, pixel-shift photos, or burst photos. That’s because the SD slot supports UHS-II, which allows for faster data transfer. The microSD slot only supports UHS-I.)

There are advantages to filling both memory card slots, but it’s not required.

The advantage of filling both slots is that it opens up options on how the second slot is used.

That’s what I’m focusing on here.

Set the primary memory card

The first thing you’ll want to do is assign a primary slot. The default is the full-size SD card slot, and in most cases, that’s a good choice.

But if you want to reverse it, to make the microSD card slot the primary slot, you can find this under:

PHOTO SHOOTING MENU (the camera icon) > Primary slot selection

It’s a simple choice. The default is SD. To change it, just choose microSD instead.

Set the secondary slot function (how the second card is used)

With a second memory card in the camera, you get some extra features.

You can find these under:

PHOTO SHOOTING MENU (the camera icon) > Secondary slot function

Overflow

The default setting is overflow.

And it’s pretty simple: if you run out of storage space on the first card, it will automatically continue on the second card.

Backup

The backup option creates an identical duplicate on each card. It’s a great in-the-field safety precaution. Or if you’re shooting with an assistant, you can hand off one card to them for either safekeeping or for some immediate processing while you keep shooting.

Critical warning: The “Backup Mode” bottleneck

There is one specific scenario where the Zf’s mixed card slots can cause a problem.

If you set the camera to “Backup” mode (writing the same file to both cards simultaneously) and you shoot high-bitrate video (4K60p), the camera is limited by the speed of the slowest card. You can run into much the same issue if you’re shooting in the high-speed Pre-Release Capture (C30) mode.

Since the microSD slot is slower (UHS-I), it can become a bottleneck. Even if you have a blazing fast V90 card in Slot 1, the buffer can only empty as fast as the microSD card in Slot 2 accepts the second copy, so a long burst stalls sooner than it would writing to the SD card alone.

My Advice: If you shoot long bursts, leave the Secondary Slot function on “Overflow” rather than “Backup” — or, if you want the redundancy, put a V30 microSD card in Slot 2 and test how deep your bursts actually run before you rely on it. For video, this menu isn’t the setting to change at all: point Destination (in the video recording menu) at Slot 1.

RAW primary – JPEG secondary

This applies if you’re using the RAW + JPEG option in the Image Quality setting. It will save a RAW version of the image onto the primary card and a JPEG version onto the secondary card.

If you have a different Image Quality setting, such as RAW or JPEG/HEIF, it will save two copies of the same file, one on each card. In other words, it will be functionally the same as the Backup option.

There is a prerequisite for this option to be available: you’ll have to have the Tone Mode set to SDR (which is the default setting). If you set the Tone Mode to HLG, the available option will instead be RAW primary – HEIF secondary. That’s because HLG can only save in HEIF format.

If you have an Image Quality setting for a different kind of file (i.e., RAW), it becomes functionally the same as Backup.

JPEG primary – JPEG secondary

This saves a JPEG copy to each memory card.

So the natural question is how this is any different from using the Backup setting above. And in this case, it’s because the second copy is a smaller version and at the JPEG basic setting. So it’s a smaller, lighter-weight version.

You’ll notice the small arrow to the right of the option. If you drill down to that, you get an option of saving the second copy as either a Medium (4528×3024 pixels) or Small (3024×2016 pixels) file (both are with JPEG basic compression settings).

This smaller, lighter-weight version can be useful in some workflows, especially for photojournalists or sports photographers who need to transmit files quickly from a location. But it’s worth emphasizing that with this specific combination of settings, the secondary slot isn’t just a backup in this mode; it’s creating a lower-quality file.

If you have an Image Quality setting for a different kind of file (i.e., RAW), it becomes functionally the same as Backup.

Best settings by workflow

Workflow	Recommended Slot 2 Setting	Why?
General Travel	Overflow	Maximizes storage; set-and-forget.
Wedding / Paid Work	Backup	Safety first; if one card dies, you have a copy.
Sports / Action	JPEG Primary – JPEG Secondary	Send small JPEGs to editor immediately; keep high-res on Card 1.
High-Res Video	Overflow (Video to Slot 1)	Avoids the microSD speed bottleneck.

Things worth knowing

There are some fine-print quirks worth knowing about.

• If you have anything other than Overflow selected, the number on the top screen that shows how many images you can fit on the remaining space will refer to the memory card with the least remaining space. When the first card runs out of space, the shutter will stop working.
• All of the above refer to saving photos. There’s a separate section for specifying where video files should be saved.
  
  You can find it under:

VIDEO RECORDING MENU (video camera icon) > Destination

• I recommend setting the Video Destination to Slot 1 (SD) by default. Since Slot 1 is UHS-II and Slot 2 is UHS-I, you almost always want high-bitrate video going to the faster SD card to avoid buffer issues or stopped recordings.

• Technically, it’s possible to use two microSD cards in the Nikon Zf by using one in a microSD-to-SD cartridge adapter. However, I don’t typically recommend that approach because I’ve seen too many times something has gone wrong by adding the extra potential failure point of the adapter.

It’s also worth knowing what that adapter does and doesn’t do. It’s a passive shell — it re-routes the pins to the full-size footprint and has no controller of its own, so it adds no speed. A UHS-I microSD card in an adapter sitting in the UHS-II SD slot is still a UHS-I card running at UHS-I speeds.

Which memory cards should you get?

The good news is that neither of these is an exotic memory card format, and you can get fast, large-capacity cards at very reasonable prices. So not only does it make sense to fill both slots, but you can do so without it costing an arm and a leg.

I have a much more detailed post on memory cards for the Nikon Zf, but here are some quick recommendations for each slot.

Something you might notice with these is that the full-size SD cards listed are faster but their maximum storage capacities are lower. And these microSD cards (which are UHS-I) are slower but have higher maximum storage capacities.

One thing not to spend money on is a UHS-II microSD card for Slot 2. UHS-II needs a second row of pins on both the card and the slot, and the Zf’s microSD slot is UHS-I only, so a UHS-II microSD card just falls back to UHS-I speeds. The bus always runs at the speed of whichever is slower, card or slot, which is also why a UHS-II SD card only pays off in Slot 1.

If you’re using the Overflow setting, the cards do not need to be the same storage capacity, so you can have a lower-capacity (but faster) card in the full-SD slot and a slower but higher-capacity card for overflow in Slot 2.

If you’re using any of the other options from above, the shutter will only work so long as there is space on both cards. Put another way, as soon as one card fills up, the shutter will stop working, even if there’s plenty of space still on the other card. So, in that case, it makes sense to use matching storage capacities, but it’s not technically a requirement.

Full-size SD cards

microSD cards

You can see some of the photos I’ve taken with the Nikon Zf in these posts:

– Nikon Zf Sample Images (a varied collection of color and black and white photos taken under various conditions)
– Nikon Zf High ISO Sample Images (focusing specifically on high-ISO images taken in low-light conditions)
– Nikon Zf ISO Range Sample Images (sequences shot throughout the ISO range to help with assessing image quality at various ISOs)
– Shooting Panoramas with the Nikon Zf (focusing on stitched panoramas)