What do SDHC memory card class designations mean?
April 3rd, 2008 by Scot Drew
You may have noticed that SDHC memory cards are available in different speed classes (2, 4 and 6). Each class designation directly reflects the minimum sustained Data Transfer Rate (DTR) of the card.
- Class 2: minimum DTR of 2 MB/second
- Class 4: minimum DTR of 4 MB/second
- Class 6: minimum DTR of 6 MB/second
These cards are the perfect solution for today’s SDHC-compatible devices that run MPEG-2, MPEG-4 and other high-quality video compression used by HD and DVD video.
May 6th, 2008 at 10:08 am
[...] the video. Now maybe there is some user error involved but my experience tells me the problem is in the speed of the card as my old Lexar platinum card worked fine for [...]
June 26th, 2008 at 12:59 pm
Sandisk sells the Class 4 “featuring fast 15MB/sec Read/Write speeds”. So which is it, 4MB/sec or 15MB/sec? Shouldn’t this be a class 15? or at least a class 6?
SanDisk Ultra® II SDHC 32GB High Performance Card
SDSDRH-032G-A11
High speed card featuring fast 15MB/sec Read/Write speeds
http://www.sandisk.com/Products/ProductInfo.aspx?ID=2582
June 27th, 2008 at 3:08 pm
Based on information provided by Wikipedia the speed class rating is the minimum write speed. Sandisk is claiming up to 15MB write speed.
The SD Speed Class Ratings specify the following minimum write speeds based on “the best fragmented state where no memory unit is occupied”:
 Class 2: 2 MB/s
 Class 4: 4 MB/s
 Class 6: 6 MB/s
SDHC cards will often also advertise a maximum speed (such as 133x or 150x) in addition to this minimum Speed Class Rating. One critical difference between the Speed Class and the maximum speed ratings is the ability of the host device to query the SD card for the speed class and determine the best location to store data that meets the performance required.
“Maximum speed” ratings are unofficial and have no formal evaluation process.
Source: Wikipedia http://en.wikipedia.org/wiki/Secure_Digital_card
Hope this helps.
July 5th, 2010 at 9:01 am
[...] quickly so you can move on to the next shot. Memory card speed is displayed on packaging with a Class rating. A Class 6 SD card is currently the [...]
September 12th, 2010 at 6:36 am
what is the best maximum capacity and maximum clas memory card and which make is the best of my foll 2 nokia handsets :
Nokia N 97 Mini
Nokia 5800 music xpress
December 12th, 2010 at 12:09 pm
my Samsung digital camcorder is giving me an error message from 2 – 7 minutes or less, depending on the resolution…”Low Speed Card Please record a lower resolution” It doesn’t matter what resolution I use either.
I saw a Extreme SanDisk class 10, 32GB, SDHC card rated at 30MB/s. Would this work in my Camera?
December 12th, 2010 at 12:15 pm
Oh and I have a PNY Optima, class 4, 8GB, 120 Min. HD, SDHC card in it now.
December 13th, 2010 at 10:58 am
Hi Ernie,
The owner’s manual for your camcorder should include requirements for compatible memory cards. Most HD camcorders require a class 6 or higher rated SDHC memory card for recording HD resolutions. With the class 4 card you currently have you will need to set the Video Resolution of the camcorder to 480/60p. Using a SDHC memory card such as the Delkin Devices DDSDPRO3-32GB 32GB Class 10 SDHC memory card will allow you to record at the higher HD resolutions.
January 23rd, 2011 at 12:27 am
I purchased a Nikon D5000 with an HD video facility. The sales assistant recommended a Class 6 card, which I bought. Now I find that the videos will not play on my Macintosh Computer in any application. Could the problem be the card? And will a Class 10 card help?
January 24th, 2011 at 3:15 pm
Hi June,
The question might be more which Mac you are using. It has to be an Intel Core duo processor or better, running iLife ’11 I believe. Or a version of final cut might work as well. The problem cannot be the card as it is just a data storage device. The speed will only effect what you can record. The difficulty you’re having is more likely a compatibility issue between the recorded video format and your computer.
March 27th, 2011 at 7:01 am
I am trying to decide if I should buy a class 6, which I have for my panasonic camera or a class 10 for my husband’s canon camera that takes video also. Is there that much difference and is a class 10 always better than a class 6? Thanks.
April 8th, 2011 at 3:53 pm
Hi Diana,
Good questions. To start with your class 6 SDHC memory card has a data transfer rate of 22MB per second while a class 10 card is rated at 23MB per second and while technically the class 10 card will have a slight speed advantage for most cameras there will not be a noticeable difference.
Thanks,
Matt
August 1st, 2011 at 1:01 pm
I ordered a SanDisk Ultra SDHC 16GB, Class 4, 15 MB/S write speed (?) for a camcorder. I received a SanDisk 16GB, Class 6, 20 MB/S write speed. Apparently an upgrade or is Sandisk just recognizing that the card should be a Class 6? I have also asked SanDisk. (No price difference).
To June with the Nikon – I also have a Nikon (not a D5000 but a recent model) and a MacBook (W Intel Core 2 Duo). Videos from camera upload into iPhoto (iLife11 or earlier version) not iMovie. Videos then can be imported into iMovie for editing. Photos stay in iPhoto. This should work OK. No need to use the Nikon software for this.
October 9th, 2011 at 3:23 am
someone should tell these camera companies to get their act together..
make their cameras specs known…they do not..
December 21st, 2011 at 10:08 am
i have nikon camera recent model i bought sd card class 10 pro 16 GB i want to know which one is better for quality and longer viedo full hd quality sd pro 16 GB class 10 or cd 8 GB class 6 ?
December 21st, 2011 at 12:50 pm
Hi Shervin,
That’s a great question. According to the owner’s manual for your P500 camera Nikon recommends a minimum class 6 rated SD memory card for recording videos. They also state the maximum recording time for a single video is either 4GB or 29 minutes. The image quality will not be affected by the memory card. However, the class 10 rated card will allow data to be recorded faster which reduces the possibility that the camera will need to stop recording because the buffer is full.
More complete details can be found on pages 157-166 in the camera owner’s manual.
Please let us know if you have any additional questions.
Matt