CFe/SD card logic

This has probably been done to death since the Z6ii came out, but I'm struggling to find the best answer...

I'm a part-time pro that mainly does events. I still have my trusty D750 that I'm about to chop in for a Z6iii.

Now, the Z6ii/iii has dual slots of course, and everyone says that there's no point messing around with ancient SD cards as the CFe is so much faster etc. Which I get. But from what I understand, if you use the SD card in backup mode, the speed will be limited to the slowest card.

As someone that doesn't risk not using both slots in backup mode, am I reading this correctly that, essentially, the SD backup in the ii/iii is therefore pointless if you want the speeds of the super-duper, super expensive CFe? It's one or the other, speed OR backup, but not both?

What does everyone in pro situations do? Go for speed and assume CFe cards never break, or use both slots and just buy the cheapest, slowest CFe card as any speed advantage is going to waste?

Just to add, write speed has never been an issue for me with SD cards in my D750. I don't do sports or 4k video etc. I might take a burst of a handful of shots at any one time – always RAW though.

If you need the backup card as fast as the primary card you buy a Z9.

dacrema said:

If you need the backup card as fast as the primary card you buy a Z9.

Click to expand...

Presumably or a Z8? Either way, I really want a Z6 for every other reason.

My work is less critical, but another option is to copy all of the images from the CFE-B to the SD at the end of the shoot. That is what I'll be doing.

It is too bad that these cameras can't use the CFE-B as the primary and then copy the images to the SDHC automatically, maybe when the camera goes to sleep. I'm almost thinking Nikon should have gone with one CFE-B and two micro SD-II's. Maybe even an internal CFE-B or SSD.

Station Grey said:

dacrema said:

If you need the backup card as fast as the primary card you buy a Z9.

Click to expand...

Presumably or a Z8? Either way, I really want a Z6 for every other reason.

Click to expand...

A Z8 puts you in the same situation as a Z6iii, Z6ii, Z7ii, D850 or D500: one card slot is XQD/CFexpress and the other slot is UHS ii SD.

If you are fine with the D750, which has two SD card slots, that means you are not really shooting 20 fps RAW. In that case you can continue capturing RAW and put the same NEF file onto each card, and the slower SD will not slow you down anyway.

If you capture RAW at a fast frame rate so that the SD card becomes a bottleneck, and those images are important, my solution is to shoot RAW + JPEG: put the RAW (NEF) files onto the CFexpress/XQD card and JPEG files onto the SD card. You can adjust the JPEG quality so that the SD card won't be a bottleneck, but unless you have a really slow SD card, JPEG fine should be ok. However, the fastest V90 type SD cards tend to be more expensive than CFexpress Type B cards, on a per G basis, and yet the SD cards are slower.

In such a set up, you have your RAW files on the CFexpress card, which are very reliable, but in the unlikely event that the card fails, you still have a JPEG on the SD card. It is not ideal, but at least it is extremely unlikely that you will lose everything. That is the best practice I am aware of unless you go to a flagship camera body.

I typically just leave the SD slot open. If I have something very important, I use a Z9 and put RAW files onto both CFexpress cards.

I think the simplest logic to understand is that the slow SD card is only a problem if you are continuously shooting at the highest frame rate for long enough bursts that you fill the camera’s buffer. If that happens then frame rate slows until the buffer clears, which happens at the speed of the slowest card.

The Z6iii is said to have a buffer so large it is essentially unlimited, so unless you are standing on the shutter button in full auto an entire shoot, you won’t see an issue with the SD card being a bottleneck.

With my Z8 I can shoot about 40 frames of RAW before I start to see slowdown, and if I simply release the shutter button and mash it right back down the camera has already recovered. But I seldom do that.

For all intents and purposes this is a non-issue.

Station Grey said:

This has probably been done to death since the Z6ii came out, but I'm struggling to find the best answer...

I'm a part-time pro that mainly does events. I still have my trusty D750 that I'm about to chop in for a Z6iii.

Now, the Z6ii/iii has dual slots of course, and everyone says that there's no point messing around with ancient SD cards as the CFe is so much faster etc. Which I get. But from what I understand, if you use the SD card in backup mode, the speed will be limited to the slowest card.

As someone that doesn't risk not using both slots in backup mode, am I reading this correctly that, essentially, the SD backup in the ii/iii is therefore pointless if you want the speeds of the super-duper, super expensive CFe? It's one or the other, speed OR backup, but not both?

What does everyone in pro situations do? Go for speed and assume CFe cards never break, or use both slots and just buy the cheapest, slowest CFe card as any speed advantage is going to waste?

Click to expand...

This is not exactly right.

The camera writes images sequentially - the first image to the primary card, then the backup copy to the secondary slot. Each card has a write speed, and the time to write to both cards is the sum of writing to card 1 and then to card 2.

Yes - the SD card is the bottleneck but it's really because you are writing the file twice, and the second copy to the SD card takes a lot longer than the first copy to CFExpress. The top end speed for actually writing on UHS-II SD cards with a Z6iii is around 145 MB/s - which translates to around 4.5 fps. The top speed for a fast CFExpress card is more than 20 fps or 1100 MB/s. So a one second burst of 20 images will take approximately 5.5 seconds to write to both cards with very fast cards - and longer if you have a slow card.

You have several choices. You can reduce the size of your file, but that does add processing time. It's enough using HEIF or JPEG to make a big difference on the SD card slot and therefore to the time it takes to write to both files.

The frame rate is the same whether or not you use backup mode until the buffer fills. But clearing that buffer means writing to both cards - including that slow SD card.

Once the buffer fills, the camera slows to the speed at which it can write images to free up space and use that space for more images. If you write an image to the card, that space is freed up. When I tested the Z7ii I found that simply freeing space in the buffer did not allow peak speed - it operates at a reduced speed until the buffer is completely cleared. I have not tested the Z6iii. But this means your shooting speed is limited for longer in Backup mode because it could take 10+ seconds to clear the buffer. Shooting to just a single CFExpress card, the buffer never fills and you can shoot at 20 fps indefinitely.

Station Grey said:

This has probably been done to death since the Z6ii came out, but I'm struggling to find the best answer...

I'm a part-time pro that mainly does events. I still have my trusty D750 that I'm about to chop in for a Z6iii.
[...]
What does everyone in pro situations do? Go for speed and assume CFe cards never break, or use both slots and just buy the cheapest, slowest CFe card as any speed advantage is going to waste?

Click to expand...

Everyone is probably a little different, but the way I see it: If what you're shooting only happens once, back it up. Full stop.

Weddings and events, I back up everything I shoot to both card slots, and I'll get other redundant photos captured either on other camera bodies (I use two) or via a second shooter. Maybe I'm paranoid, but all it takes is one lost wedding shoot to ruin your business and I don't want to be on social media, TikTok, or elsewhere for the wrong reasons

For the above reason, I have no issue finding and buying the fastest reliable SD card I can to pair with my CFexpress cards. Of course, even the best SD card absolutely pales in comparison to any modern CFexpress card - but in practice even over-shooting like a crazy person on a Z8 has never been an issue. The camera may have slowed down as I've hit the buffer, but it's never stopped completely, and I don't believe I've ever missed a shot because of this.

If you have a Z6iii your files would be about half the size of the Z8/Z9 in the same RAW compression mode, so unless you're bursting an incredible amount, at 20fps+, I don't think you would have an issue with a high-end SD card.

Just remember that JPG and HEIF don't give you all of the nifty if not invaluable Lightroom features. I hope they catch up soon, but I'm not going to hold my breath either. They need to treat HEIF like RAW.

Probably don't want to hear this, but pros in pro situations shoot with a Z9, which can backup to another CFeB card. If you are routinely shooting bursts of long enough duration that you are filling the buffer, it is what it is.

You can shoot with more raw compression (HE or HE*), to make the buffer last longer.

Another alternative is to shoot raw to the CFeB, and jpeg to the SD. This should improve throughput, while still giving a good measure of backup, but I have never tried it to know what the actual difference is.

Station Grey said:

This has probably been done to death since the Z6ii came out, but I'm struggling to find the best answer...

I'm a part-time pro that mainly does events. I still have my trusty D750 that I'm about to chop in for a Z6iii.

Now, the Z6ii/iii has dual slots of course, and everyone says that there's no point messing around with ancient SD cards as the CFe is so much faster etc. Which I get. But from what I understand, if you use the SD card in backup mode, the speed will be limited to the slowest card.

As someone that doesn't risk not using both slots in backup mode, am I reading this correctly that, essentially, the SD backup in the ii/iii is therefore pointless if you want the speeds of the super-duper, super expensive CFe? It's one or the other, speed OR backup, but not both?

What does everyone in pro situations do? Go for speed and assume CFe cards never break, or use both slots and just buy the cheapest, slowest CFe card as any speed advantage is going to waste?

Click to expand...

As you said, it's either going to be speed or backup (security) -- unfortunately it's hard to get both and not impact burst shooting too much unless you d rop your frame rate or lower your file format to HEIF compressed RAW (or just shoot JPEG). On a good note, CFE/XQD cards are a bit more reliable and robust than SD cards, so you shouldn't have any issues providing you buy quality, certified cards (Delkin Black may be an exception as they are not technically certified/tested for the Z8 but a lot of people have them and swear by them, and I'd avoid sandisk CFE cards even though they are certified/tested---they're just slow and tend to run hot and that can cause problems. Lexar and ProGrade are the other two brands to consider too).

--
PLEASE NOTE: I usually unsubscribe from forums and comments after a period of time, so if I do not respond, that is likely the reason. Feel free to PM me if you have a questions or need clarification about a comment I made.

skyrunr said:

My work is less critical, but another option is to copy all of the images from the CFE-B to the SD at the end of the shoot. That is what I'll be doing.

It is too bad that these cameras can't use the CFE-B as the primary and then copy the images to the SDHC automatically, maybe when the camera goes to sleep. I'm almost thinking Nikon should have gone with one CFE-B and two micro SD-II's. Maybe even an internal CFE-B or SSD.

Click to expand...

Agreed... manually doing a backup is an option (is that even a function though?)... and yes, doing backups on the fly would be best for me, but I suppose that takes processing power that might be needed for bursts.

As mentioned in another post above, the camera's buffer might actually negate the issue after all though.

shuncheung said:

Station Grey said:

dacrema said:

If you need the backup card as fast as the primary card you buy a Z9.

Click to expand...

Presumably or a Z8? Either way, I really want a Z6 for every other reason.

Click to expand...

A Z8 puts you in the same situation as a Z6iii, Z6ii, Z7ii, D850 or D500: one card slot is XQD/CFexpress and the other slot is UHS ii SD.

Click to expand...

Yeah, I realise now the difference between Z8/Z9, I hadn't checked before. I assumed the same just because everyone describes the Z8 as a mini Z9

shuncheung said:

If you are fine with the D750, which has two SD card slots, that means you are not really shooting 20 fps RAW.

Click to expand...

Well that's true as the D750 max is 6.5 fps

shuncheung said:

In that case you can continue capturing RAW and put the same NEF file onto each card, and the slower SD will not slow you down anyway.

If you capture RAW at a fast frame rate so that the SD card becomes a bottleneck, and those images are important, my solution is to shoot RAW + JPEG: put the RAW (NEF) files onto the CFexpress/XQD card and JPEG files onto the SD card. You can adjust the JPEG quality so that the SD card won't be a bottleneck, but unless you have a really slow SD card, JPEG fine should be ok. However, the fastest V90 type SD cards tend to be more expensive than CFexpress Type B cards, on a per G basis, and yet the SD cards are slower.

In such a set up, you have your RAW files on the CFexpress card, which are very reliable, but in the unlikely event that the card fails, you still have a JPEG on the SD card. It is not ideal, but at least it is extremely unlikely that you will lose everything. That is the best practice I am aware of unless you go to a flagship camera body.

Click to expand...

I never use JPEGs, but you're right that they'd be fine as a backup for emergencies, so this is a method I might test. Still a shame as I like my current old camera having full RAW backups - albeit at a slow burst speed.

PLShutterbug said:

I think the simplest logic to understand is that the slow SD card is only a problem if you are continuously shooting at the highest frame rate for long enough bursts that you fill the camera’s buffer. If that happens then frame rate slows until the buffer clears, which happens at the speed of the slowest card.

The Z6iii is said to have a buffer so large it is essentially unlimited, so unless you are standing on the shutter button in full auto an entire shoot, you won’t see an issue with the SD card being a bottleneck.

With my Z8 I can shoot about 40 frames of RAW before I start to see slowdown, and if I simply release the shutter button and mash it right back down the camera has already recovered. But I seldom do that.

For all intents and purposes this is a non-issue.

Click to expand...

This is the most useful reply for me, and something I hadn't really considered.

Essentially, 20fps is something I'd use very very rarely... but nice to have available on occasion. If the buffer is large enough then presumably it'll be plenty for the occasional burst anyway, and then it can write at its leisure.

I guess the conclusion is that I'll have to do some testing when I get the camera and both cards... if the buffer can handle a few bursts then I'll use the SD for RAW backup... if not then I'll consider JPEG backup.

Thanks all, that was very useful. And yes, I understand that pros would just buy the Z9, but my point was that even a lowly mid-range D750 was capable in its day of shooting RAW to two equal cards at full speed, so it seems a annoying that the improvements in burst rate haven't been matched with dual fast cards in the equivalent model. But perhaps, as above, it's a non-issue. Could it be even that a fast CFe card only really comes into its own as being necessary for video?

ericbowles said:

Station Grey said:

This has probably been done to death since the Z6ii came out, but I'm struggling to find the best answer...

I'm a part-time pro that mainly does events. I still have my trusty D750 that I'm about to chop in for a Z6iii.

Now, the Z6ii/iii has dual slots of course, and everyone says that there's no point messing around with ancient SD cards as the CFe is so much faster etc. Which I get. But from what I understand, if you use the SD card in backup mode, the speed will be limited to the slowest card.

As someone that doesn't risk not using both slots in backup mode, am I reading this correctly that, essentially, the SD backup in the ii/iii is therefore pointless if you want the speeds of the super-duper, super expensive CFe? It's one or the other, speed OR backup, but not both?

What does everyone in pro situations do? Go for speed and assume CFe cards never break, or use both slots and just buy the cheapest, slowest CFe card as any speed advantage is going to waste?

Click to expand...

This is not exactly right.

The camera writes images sequentially - the first image to the primary card, then the backup copy to the secondary slot. Each card has a write speed, and the time to write to both cards is the sum of writing to card 1 and then to card 2.

Yes - the SD card is the bottleneck but it's really because you are writing the file twice, and the second copy to the SD card takes a lot longer than the first copy to CFExpress. The top end speed for actually writing on UHS-II SD cards with a Z6iii is around 145 MB/s - which translates to around 4.5 fps. The top speed for a fast CFExpress card is more than 20 fps or 1100 MB/s. So a one second burst of 20 images will take approximately 5.5 seconds to write to both cards with very fast cards - and longer if you have a slow card.

You have several choices. You can reduce the size of your file, but that does add processing time. It's enough using HEIF or JPEG to make a big difference on the SD card slot and therefore to the time it takes to write to both files.

The frame rate is the same whether or not you use backup mode until the buffer fills. But clearing that buffer means writing to both cards - including that slow SD card.

Once the buffer fills, the camera slows to the speed at which it can write images to free up space and use that space for more images. If you write an image to the card, that space is freed up. When I tested the Z7ii I found that simply freeing space in the buffer did not allow peak speed - it operates at a reduced speed until the buffer is completely cleared. I have not tested the Z6iii. But this means your shooting speed is limited for longer in Backup mode because it could take 10+ seconds to clear the buffer. Shooting to just a single CFExpress card, the buffer never fills and you can shoot at 20 fps indefinitely.

Click to expand...

I just did a quick test of a 100 image burst writing to a Delkin Power CFEXpress 1TB card. Writing to the CFExpress card only, it took 5 seconds to shoot 100 NEF frames. Writing to the CFExpress card and a UHS-i SD card (a UHS-I Sandisk 95MB/s - a very fast UHS=I card) in backup mode, it took 13.8 seconds because the high frame rate quickly filled the buffer and could only write images as buffer space was freed up. With a fast SD card (Lexar 1667x UHS-II 256 GB), shooting in backup mode for 100 images took just 5.6 seconds, but the buffer did fill at the end of the burst so a longer burst would be more adversely affected.

There is a big difference in slow and fast CFEXpress cards. Here is a screen shot of test results for two CFExpress cards and an XQD card in the Z7ii. The Z7ii a slower processor and can't use the added speed of the fastest CFExpress cards like the card I used for testing. The left axis is frames shot in a full second, and the horizontal axis is the sequential second of a 30 second burst. As you can see, the Delkin Power 128 GB card was about the same as the Lexar XQD card, but the ProGrade Gold 128 GB card was very slow. You won't see this kind of variation in a Z6iii if the card is reasonably fast, but I found the ProGrade Gold 128GB card to be exceptionally slow in testing the Z7ii, Z6, and D850.







--
Eric Bowles
https://bowlesimages.com/

ericbowles said:

ericbowles wrote:I just did a quick test of a 100 image burst writing to a Delkin Power CFEXpress 1TB card. Writing to the CFExpress card only, it took 5 seconds to shoot 100 NEF frames. Writing to the CFExpress card and a UHS-i SD card (a UHS-I Sandisk 95MB/s - a very fast UHS=I card) in backup mode, it took 13.8 seconds because the high frame rate quickly filled the buffer and could only write images as buffer space was freed up. With a fast SD card (Lexar 1667x UHS-II 256 GB), shooting in backup mode for 100 images took just 5.6 seconds, but the buffer did fill at the end of the burst so a longer burst would be more adversely affected.

Click to expand...

That's excellent, thank you very much!

By chance, my current (twin) SD cards in my D750 are those exact USH-I Sandisks, so that's a very interesting test.

I suppose that proves that, ignoring video, a fast SD card will be more than enough for almost anyone's real-world stills shooting. In reality, even my Sandisks would probably be plenty for the kind of shooting I do, but to take advantage of the newer tech I'm spending out on (plus my Sandisks being many years old), perhaps it's worth buying a newer, faster SD card like yours, setting to backup and having that peace of mind, at a little cost.

Just checking, but your test was with RAW I assume?

Thanks again.

Station Grey said:

Station Grey said:

ericbowles wrote:I just did a quick test of a 100 image burst writing to a Delkin Power CFEXpress 1TB card. Writing to the CFExpress card only, it took 5 seconds to shoot 100 NEF frames. Writing to the CFExpress card and a UHS-i SD card (a UHS-I Sandisk 95MB/s - a very fast UHS=I card) in backup mode, it took 13.8 seconds because the high frame rate quickly filled the buffer and could only write images as buffer space was freed up. With a fast SD card (Lexar 1667x UHS-II 256 GB), shooting in backup mode for 100 images took just 5.6 seconds, but the buffer did fill at the end of the burst so a longer burst would be more adversely affected.

Click to expand...

That's excellent, thank you very much!

By chance, my current (twin) SD cards in my D750 are those exact USH-I Sandisks, so that's a very interesting test.

I suppose that proves that, ignoring video, a fast SD card will be more than enough for almost anyone's real-world stills shooting. In reality, even my Sandisks would probably be plenty for the kind of shooting I do, but to take advantage of the newer tech I'm spending out on (plus my Sandisks being many years old), perhaps it's worth buying a newer, faster SD card like yours, setting to backup and having that peace of mind, at a little cost.

Just checking, but your test was with RAW I assume?

Thanks again.

Click to expand...

Yes - Z6iii shooting RAW.

Those older UHS-I cards are good for a D750 or even a Z50 that can't use UHS-II speed. But in the Z6iii or Z8, I would certainly get a UHS-II SD card for the second slot. I was surprised how little adverse impact there was from using Backup mode with very fast cards.

Thanks

ericbowles said:

{snip}

I just did a quick test of a 100 image burst writing to a Delkin Power CFEXpress 1TB card. Writing to the CFExpress card only, it took 5 seconds to shoot 100 NEF frames. Writing to the CFExpress card and a UHS-i SD card (a UHS-I Sandisk 95MB/s - a very fast UHS=I card) in backup mode, it took 13.8 seconds because the high frame rate quickly filled the buffer and could only write images as buffer space was freed up. With a fast SD card (Lexar 1667x UHS-II 256 GB), shooting in backup mode for 100 images took just 5.6 seconds, but the buffer did fill at the end of the burst so a longer burst would be more adversely affected.

{snip}

Click to expand...

Was that test with High Efficiency* ? Those are much smaller than the lossless compressed raws, and should write to the SD card proportionately faster than lossless.