What SD card for the D7100?

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Liteman

Senior Member
I've just bought a D7100 and a couple of Sandisk 32Gb 30MB/s cards. I found that the camera took a long time writing the images to the card and have now decided to change the cards for faster ones (good old Amazon have agreed to take the cards back for a full refund). I don't plan to make a lot of use of the video facility but do shoot everything in RAW and quite often use the camera in continuous shooting mode. My question is, do I need to go for the 95MB/s card or will the 80MB/s card give me sufficient write speed?
 
Horoscope Fish

Horoscope Fish

Senior Member
Well bear in mind the card can only write as fast as it's written to by your camera's buffer. Also, things like Noise Reduction can impact processing time that takes place prior to writing but delays things just the same. The D7100 has also been bashed by some as having too small a buffer, which causes a log-jam when shooting in "Continuous" modes. All this being the case I'm not sure how much an Uber fast card/s would help. Personally, I typically use San Disk Extreme's, rated at up to 45 MB/s. The key phrase here, though, is "up to". My quad-core PC writes to those cards at around 20MB/s via a USB 2.0 port. Just recently I scored a pair of 32GB Samsung cards that are rated at something like 48MB/s for about half of what the San Disk cards go for.
 
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WayneF

Senior Member
Liteman said:
I've just bought a D7100 and a couple of Sandisk 32Gb 30MB/s cards. I found that the camera took a long time writing the images to the card and have now decided to change the cards for faster ones (good old Amazon have agreed to take the cards back for a full refund). I don't plan to make a lot of use of the video facility but do shoot everything in RAW and quite often use the camera in continuous shooting mode. My question is, do I need to go for the 95MB/s card or will the 80MB/s card give me sufficient write speed?
Click to expand...

You need to understand the ratings used on the cards. The 30MB ratings apply to the read speed, when in your computer USB slot, if the USB is fast enough. The write speed is more nearly the Class 10 number, which means 10MB/second, minimum. Technically, Class 10 means the slowest of Read or Write is at least 10MB/second, but which is always Write.

Your link to the Ultra card says: Speed : up to 30MB/s read speed; write speed lower (write speed is always slower).

30MB/sec is about a 200X card. The X number is read speed too, being this X times 150KB/second, the original CD read speed. The memory card speed rating system probably could be improved today. :D The write speed is not well specified, since it so much depends on the device doing the writing.

Here is good link to card write speeds in cameras:

It says the Sandisk Ultra card write speed measures 13MB/second in the D7000 camera (other cameras may have different speeds). That would qualify for Class 10 being minimum of 10 MB/sec.

Now a D7100 JPG might be 16MB size, so this 13MB/sec speed should take about about 1.2 second to write. A burst of 5 files would take about 5x16/13 = 6 seconds to finish writing. A Raw file may be around 30MB, so it would take 2.3 seconds to write on this card. The test chart above says the D7000 can write 27MB/sec with a fast enough card (if that might be important). That is a 95 MB/sec card, which again is read speed, but to which the D7000 can write 27MB/sec, it says (it is reliable). If you only take one image every minute or so, how could it matter?

But for example, the D800 can write about 69 MB/second to the fastest compact cards. It can depend on what is doing the writing.

Video is much slower, it has the entire recording time to write the file, and any Class 10 card is plenty for video. Faster cannot help video (it only records so fast).
 
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Liteman

Senior Member
Thank you both for responding. I looked at WayneF's link which adds to the confusion by it's sheer size, however it did allow me to see relative data for the various cards. I have plumped for the Lexar Professional which probably means I've got more money than sense but it does seem to have some pretty good reviews, and after spending £850 on a camera it seemed a bit daft to skimp on the "business end" of the kit - a bit like the old days of good enlargers with cheap lenses!
 
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WayneF

Senior Member
You will want a USB 3.0 card reader. USB 2.0 cannot go faster than almost 30MB/sec, and the 95MB/sec is the read speed. You can appreciate read speed when you have several hundred files on the card to be downloaded.
 
Patrick M

Patrick M

Senior Member
It also makes a big difference if you take RAW as well. If like me, you're shooting to get a series of possible snaps for a web share, then use just JPEg, then Basic and Small. That's the smallest you can get and also the fastest for writing through the buffer. It's worth experimenting.
 
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NikonVincent

Senior Member
i read some expert saying that the amount of time the buffer takes to "dump" a full buffer onto the SD card is heavily dependent on the SD card's speed. hence it would make sense to buy a super fast card like the Extreme Pro. i can't remember the expert who wrote that, but i believe it was Thom Hogan.

​hope this helps.
 
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WayneF

Senior Member
The 45 MB/sec and 95 MB/sec numbers are read speeds, in your card reader. You will need a USB 3.0 reader and port to achieve either maximum speed (USB 2.0 only runs maybe 30 MB/sec at most, regardless of how fast the card is). Read speed can seem important when you have a few hundred files to download.

For write speed in the camera, the write speed is less, and which depends on the card, and also on the camera model.

Here is the best data for write speed, actually tested in a D7000:

Rob Galbraith DPI: Nikon D7000

A Large Fine JPG in D7100 is around 12 MB. So if the write speed were 12MB/sec, it would take one second (after the shutter completed). A burst of five would take five seconds. If that is acceptable to you, you don't need faster.

Both the 45 MB/sec and 95MB/second are shown to write around 24MB/sec. If you need more, I think faster is not as yet available (not in SD format). The 95 card can go faster in a D800, but is limited by the D7000 camera.

A RAW file might be 20 to 28 MB, so you would feel a burst of five harder.

Video is SLOW, and is NOT a speed consideration. Nikon says (in the link you posted) that Class 6 is enough for video (6 MB/second). Video has the entire record time to write the file.


Now
 
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Liteman

Senior Member
I finally plumped for the Lexar Professional 600X (90MB/s) cards as I shoot mainly RAW which produces some pretty large files. I Took a trip to the London stage of the Tour of Britain cycle race and found that, even when using RAW the continuous shooting mode was OK to capture the action without slowing down too soon. Where the action was very fast, I switched to Jpg Fine and the shooting rate was pretty machine gun like! I take the points raised about the need to use USB3, unfortunately my PC doesn't have USB3 so download speeds aren't too fast, but its really at the shooting stage that I was looking for the extra speed, I'll just have to possess my soul with patience once I get back home to download them!
 
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