Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
Measuring SD Card Performance
Posted By: dosdan, 10-21-2010, 03:36 AM

Since there are fake SD cards available in eBay, I think it worthwhile being able to check that your SD card performs reasonably.

I've found a free performance utility on the German c't electronics magazine website. The program is very small, simple to use and has an option to show English language. It's H2TESTW.

H2testw, Download bei heise

One use is to completely fill and read back a SD card to verify both its capacity and its data integrity.

The use I want to look at here is its measurement of read & write speed.

The SD Class speed rating is good for DSLR usage because it specifies the minimum sustained write speed in MB/s. It's easy to interpret.

Class 2, 4, 6, 10 = a minimum sustained writing speed of 2, 4, 6, 10 MB/s.

Just to make things more interesting, SD speed in the specification document is measured with a MB of 10^6 (1,000,000), while the capacity is measured with a MB of 2^20 (1,048,576). See the bottom of page 6 in

Older SD cards are more difficult to interpret. They use a "x" rating e.g. 60x which is compared to the CD standard speed of 150 KB/s. So 60x is 9 MB/s. The confusing thing is that this can be either the read or write speed, and since the reading speed is usually faster than the writing speed, some manufacturers measure that. So being able to actually determine the true writing speed of an old SD card yourself is a good thing.

Here is the measured speed in MB/s of the SD cards I've got here (1000 MB test file):

Labelling Write Speed Read Speed Comments
Kingston 2 GB "0715" (YYweek) 6 13.6 Both Kingston cards look the same. Used in a Zoom H4 digital audio recorder
Kingston 2 GB "0947" 8.915.2 Used in a Samsung P&S camera
Apacer 2 GB "60x" 3.7 8.8 Used in K100DS
Apacer 8 GB Class 6 8.4 15.9 Two owned - same speed. K20D spare cards
Transcend 8GB Class 10 "20MB/s"16.220.3 K20D main card


The "60x" rating on the label is justified for the Apacer 2 GB card if you use 10^6 Megabytes: 9 MB/s. However, using the modern Class rating, this is only a Class 2 card. (There's no Class 3.)

The Apacer & Transcend 8 GB cards easily meet their class rating.

The max. reading speed of the Transcend (20.8 MB/s in 10^6 Megabytes) in my cheap A-power All-in-1 mini card reader seems like it's close to top reading speed for a USB 2 card reader. Compare the results to those measured in this translated 19 SDHC card roundup at the German Hardware-Infos website where the following 3 card readers were used:
  • SanDisk ImageMate All-in-One
  • Sapphire Card-Reader/Writer Sapphire Card-Reader/Writer
  • takeMS 64in1 Card-Reader/Writer takeMS 64in1 Card-Reader/Writer
Google Translate of SDHC roundup

The highest reading speed measured was 21,895 KB/s. If that's 2^10 Kilobytes, that's 22.4 MB/s in 10^6 Megabytes.

The question is often asked "Should I buy an expensive SD card?" I'm not into DSLR video and I don't buy top brand SD cards. If video in a DSLR is important to you than the answer may well be "Yes". However, even the Transcend Class 10 card was not expensive when I bought it off eBay from a vendor in the Isle of Man. I've never had either a electronic or mechanical failure for with a SD card, so the advice of only buying top brand-name SD cards may well be a waste of money for non-video usage.

"Should I use a Class 10 card in my camera for non-video usage?" I pull the SD card out of the camera and transfer the files via an external card reader. Doing this, the Class 10 card tested here produces a 27% faster transfer (reading) rate than the class 6 card which is obviously a good thing.


Last edited by dosdan; 03-22-2011 at 12:07 PM.
Views: 27,482
04-02-2014, 05:48 AM   #16

Join Date: Sep 2006
Location: Millstone,NJ
Posts: 6,491
SanDiskís New Extreme Pro SD UHS-II Cards are Worldís Fastest SD Cards

SanDisk has released new UHS-II SD cards with write speeds up to 250MB/s and read speeds up to 280MB/s. This new line gets its major speed boost from the UHS-II bus interface. Most SD-compatible cameras currently on the market support UHS-I, at best; however, we are just starting to see new cameras with UHS-II support (like the Fuji X-T1).

The new UHS-II bus interface offers the ability to build cards with up to 312MB/s transfer speeds, which is a big jump from the maximum theoretical speeds on the UHS-I interface at 104MB/s.

The new UHS-II cards have a second row of pins to support the higher data transfer rates. The first row of pins are identical to the standard SD cards weíve seen on the market over the past several years and allow UHS-II cards to function normally in older, non-UHS II devices. Of course, if you donít have a UHS-II compatible device, you will not see the speed benefits from the UHS-II bus interface.

UHS Speed Class symbols, such as U1 and U3, indicate minimum write speeds for real-time video recording. For UHS rated cards, you will find the numeric class rating within the letter ďUĒ on the cardís label. (See the U3 labeling in the top image.)

Compressed 4K video capture data transfer rates will vary among cameras depending on what codec the camera uses. The new U3 Speed Class should be plenty fast enough to handle Sonyís XAVC-S 4K codec (used in the new Sony FDR-AX1), which captures 4K video at a 150Mb/s data rate. The U3 Speed Class at 30MB/s minimum write speed translates to a 240Mb/s data rate. While the 30MB/s minimum write speed may seem low, itís worth noting that the SD Association has not established a speed class rating higher than U3 at the time of this cardís release.

Photographers need to keep in mind that the U1 and U3 ratings are practically meaningless for still photography. The max data transfer rates can vary widely among cards with the same U1 and U3 ratings.

Additionally, while there are UHS-I cards that offer a U3 speed class rating, it is unclear whether the U3 rating on these new SanDisk cards is valid for non-UHS-II devices. For more about SD card types and ratings, see the resource article Demystifying SD Cards.

The new SanDisk Extreme PRO UHS-II cards should be available in April in 16GB to 64GB capacities for $119.99 to $299.99.
Memory Cards, SD Cards | B&H Photo Video


  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
apacer, card, cards, class, gb, kingston, mb, mb/s, read, sd
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
k10d - can i adjust green-button-exposure measuring? teson Pentax DSLR Discussion 9 07-07-2010 08:39 AM
sd card question and Pentax K7 performance Mr. Ben Pentax DSLR Discussion 8 06-30-2010 08:28 AM
measuring dynamic range Gooshin Digital Processing, Software, and Printing 1 10-15-2009 07:01 PM
Measuring trigger voltage xandy Pentax Camera and Field Accessories 16 01-21-2008 09:48 AM
Measuring light xandy Pentax SLR Lens Discussion 21 11-13-2007 01:43 PM

All times are GMT -7. The time now is 06:55 AM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]