Different card-to-computer transfer speed rates with same card

R

RicardoAlves

New member
Hi, I use booth a Nikon D700 and a D4s, and when I'm importing the files to my internal PC hard drive i got completely different transfer rate speeds from the 2 cameras cards. I import the files via a Transcend RDF8 card Reader (USB 3.0) to my computer through the USB 3.0 port and using the Windows 7 explorer. For example, the same 8GB Sandisk Extreme Pro CF card in both cameras, gave me this results: D700: Full card loaded with +/- 290 files (NEF + JPG). Transfer rate speed to computer around 30 MB/s and takes about 4 min to import all the files! D4s: Full card loaded with +/- 190 files (NEF + JPG). Transfer rate speed to computer around 14 MB/s and takes about 12 min to import all the files! If the card capacity and speed is the same, why there there's this difference in speed rates from the files of the D700 and D4s? Does anyone have a clue? Thanks,
 
W

WayneF

Senior Member
RicardoAlves said:
Hi, I use booth a Nikon D700 and a D4s, and when I'm importing the files to my internal PC hard drive i got completely different transfer rate speeds from the 2 cameras cards. I import the files via a Transcend RDF8 card Reader (USB 3.0) to my computer through the USB 3.0 port and using the Windows 7 explorer. For example, the same 8GB Sandisk Extreme Pro CF card in both cameras, gave me this results: D700: Full card loaded with +/- 290 files (NEF + JPG). Transfer rate speed to computer around 30 MB/s and takes about 4 min to import all the files! D4s: Full card loaded with +/- 190 files (NEF + JPG). Transfer rate speed to computer around 14 MB/s and takes about 12 min to import all the files! If the card capacity and speed is the same, why there there's this difference in speed rates from the files of the D700 and D4s? Does anyone have a clue? Thanks,
Click to expand...

I have no clue, it certainly seems very surprising. Both cameras have a USB 2.0 port themselves, but if using a card reader instead, which camera would no longer be any factor. They are just files, and the card reader does its own thing. The D4S files are slightly larger, but does not seem enough to matter much. But all else equal, then the computer is surely involved in the speed though, guessing some difference in procedure?

But another question is why the fastest was only 30 MB/second? That is the USB 2.0 speed limitation, and about 30 MB/second is all we will ever see on a USB 2.0 port or reader. USB 3.0 should be much faster, I see around 110 MB/second with a Lexar USB 3.0 reader (Win7, D800, 73 files, each file about 35 MB, 2.36 GB total).

Here is a free USB card speed test: UsbFlashSpeed.com: We know everything about USB Flash speed!

It will test and show USB card and reader speed. USB speed will vary drastically with block size accessed, which it shows. Possibly each camera could format the card a bit different, but I really doubt it myself.

Looks like this: (green is read speed, red is write speed). Card is Lexar 1000x compact flash.

usb.jpg




Chkdsk would show formatting block size (in a command window, on the card reader drive):

C:\>chkdsk g:
The type of the file system is FAT32.
Volume NIKON D800 created 6/26/2014 11:47 AM
Windows is verifying files and folders...
File and folder verification is complete.
Windows has checked the file system and found no problems.
31,252,352 KB total disk space.
32 KB in 1 hidden files.
64 KB in 2 folders.
2,485,472 KB in 73 files.
28,766,752 KB are available.

32,768 bytes in each allocation unit. <<-------------<<<<
976,636 total allocation units on disk.
898,961 allocation units available on disk.
 
Last edited:
Horoscope Fish

Horoscope Fish

Senior Member
FredKingston said:
Are you sure the file sizes are the same??????
Click to expand...
This was my first thought, too...

Isn't it normally the case that the same "volume" of data will transfer faster if broken down into smaller files, versus transferring the same "volume" of data in one large file? I thought that was the case but now my head hurts and I'll admit I didn't get enough sleep last night.

That, and I think we all know I have a tendency to just make shit up.

...

...
 
W

WayneF

Senior Member
16 vs 12 megapixels. D4S raw file 14.1 MB, D700 raw file 11 MB (12 bit compressed). It does not seem a large difference, 28%, not comparable to the problem description. The disks divide both into disk sectors, probably 32KB for FAT32 flash drive, probably 4KB for NTFS hard drive. And USB also has overhead dependent on block size.

It does sound like something is bad wrong, in both cases.
 
R

RicardoAlves

New member
Thank you all for the replys and feedback!

After a couple of more testing and USB 3.0 updates in my computer (both NEC/Renesas and card reader), I can get now around 30-40 MB/s transferring the files of the D4s. Maybe there was something running on my computer when I got the 15MB/s speed rates!?

Still, there are some odd things I can't quite understand:

1- I don't see much difference in terms of speed copying files to my computer from a 30MB/s card (Sandisk Ultra) compared to a 160 MB/s card (Sandisk Extreme Pro UDMA7);

2- I don't see much difference in terms of speed copying the files to my computer from the same card (160 MB/s Sandisk Extreme Pro UDMA7) to different hard drives in my computer (WD 320GB SataII, WD 500GB SataIII and a Samsung SSD 250GB 840 EVO SataIII);

3- If I run a test using UsbFlashSpeed.com: We know everything about USB Flash speed! to my cards and hard drives the write/read speeds are much higher.

So what's the weak link in the chain?
 
W

WayneF

Senior Member
RicardoAlves said:
3- If I run a test using UsbFlashSpeed.com: We know everything about USB Flash speed! to my cards and hard drives the write/read speeds are much higher.

So what's the weak link in the chain?
Click to expand...


That's a tough question, certainly I don't know. No clue if this is correct, but ....

The difference is the speed test heroically tries all block sizes, and shows a graph about how the USB speed varies drastically with block size. Which block size does the card use?

The computer copy is influenced by the card block size, which was set up by formatting.

Again, as shown, chkdsk will quickly show the cards sector size. FAT32 ought to be 32KB.

If you are doing anything special about formatting the cards, then don't do that. Simply let the camera format them the way it knows to do it.

A camera format now and then is the best way to delete files, a clean reset so to speak.
 
Last edited:
R

RicardoAlves

New member
WayneF said:
That's a tough question, certainly I don't know. No clue if this is correct, but ....

The difference is the speed test heroically tries all block sizes, and shows a graph about how the USB speed varies drastically with block size. Which block size does the card use?

The computer copy is influenced by the card block size, which was set up by formatting.

Again, as shown, chkdsk will quickly show the cards sector size. FAT32 ought to be 32KB.

If you are doing anything special about formatting the cards, then don't do that. Simply let the camera format them the way it knows to do it.

A camera format now and then is the best way to delete files, a clean reset so to speak.
Click to expand...

I do format all my cards in camera!
 
Horoscope Fish

Horoscope Fish

Senior Member
I'd just like to point out that formatting your SD card in your camera does not accomplish the same thing, nor is it the same thing as, formatting an SD card in your computer whether it be a MAC or PC. We're talking about two things here:

1) The Native File Format: It happens to be a format called FAT32. It stands for File Allocation Table. Others formats that are used in other applications are FAT16 and NTFS but SD cards, and your camera, use FAT32. It's a standard. You can't write anything to an SD card that has not been formatted because the formatting is what creates the underlying structure. Formatting is like taking a blank sheet of paper and turning it into graph paper. Each little box on our sheet of graph paper is now a container for data. Without those boxes our blank sheet of paper can't organize anything. Our SD cards are blank sheets of paper until they are formatted using FAT32. This step turns our blank SD card into a card that can hold data using a folder system. It doesn't HAVE a folder system yet though because different devices (cell phones for example) use different folder systems. This is why the device has to create it's own folder system. It will do so on the framework of FAT32 (the grid-lines on our sheet of paper).

2) The Folder System: The folder system is written to the card only after the card has been formatted (turned into a sheet of graph paper). The folder system uses, organizes and keeps track of which boxes on our graph paper already hold data, what data they hold and what boxes can hold new data. Fortunately SD cards come from the factory already formatted in FAT32 for us so most of us have never had to deal with formatting.

The crucial difference is this: When you "format" the card in-camera what you're really doing is re-creating the file-system, or emptying out all the boxes on our grid paper. The grid-lines themselves remain untouched and unchanged. If you want to actually reformat the SD card, if you want to erase all the grid-lines and start with a truly fresh sheet of paper, you HAVE to reformat the SD card in your computer using the FORMAT command (no, not "Quick Format", that's not the same thing). Formatting your SD card in your computer is the ONLY way to truly erase the card and start from scratch. What your camera calls "formatting" is actually overwriting the existing folder structure. Which is fine, but it's a totally different operation than reformatting the card. The folder-system I reformat pretty much before every new shooting session. I re-format my SD cards maybe two or three times a year.

....
 
Top