I may write an instructional blog about digital photography, but that doesn’t mean there aren’t lessons to be learned every day. For example, I learned this week that the kind of flash memory card you buy matters drastically more than I thought it did.
Before today, I thought that the speed of your memory card was primarily set by what type of memory card it was, whether it was CF or SD or SDHC or that kind of thing. It frustrated me to still be using a camera that takes SD because in my case, it was agonizingly slow.
Sure a person could go out and by an expensive Extreme IV card or some thing like that, but I thought only professionals would notice the difference. After all, its the same type of memory, how big could the difference be right? Huge!
To illustrate what I’m talking about I am going to start by briefly talking about the kind of flash memory that most camera’s use. Usually if you have a digital camera you will use one of two main kinds of memory cards. SD cards are used for consumer level (and please don’t take that to mean inferior quality or bad) camera’s, while professionals use CF cards almost exclusively. There are exceptions to this rule, but with recent higher capacities in SD cards it will usually hold at least for the camera’s now on the market.
My camera uses SD (which stands for Secure Digital in case you’re curious) cards. It is a smaller card that allows the camera itself to be smaller. My camera is older and cannot support cards larger than 2gb, and not even some of those, but newer camera’s should be able to support larger capacities like 4 and 8 gigabytes.
Other cameras use CF (Compact Flash) cards, which despite their name are in fact larger than SD cards. These larger cards allow for higher capacities and faster read and write speeds, though as I recently found out, newer SD cards are narrowing the gap.
For my discovery to make any sense we have to talk about what read and write speeds are and why they matter.
As the name implies, read and write speeds are a measurement of how fast a card can store data (write speed) and how fast it can transfer it back out (read speeds). The way these speeds are measured is usually in one of two ways. The first way, that I don’t enjoy very much, is as a multiplier of “x”, i.e. 1x, 2x and so on. It can be difficult to find out exactly what 1x is, but it’s usually taken to mean 150kb/s, or 150 kilobytes per second. Cards now come in speeds like 60x or 20x with some on either side of that figure. A card with an x multiplier of 60 has a rated speed of about 9mb/s or 9 megabytes per second (One megabyte being about 1,000 kilo bytes).
The second way cards are rated, and the way I will use, is to just give the speed in kilobytes or megabytes per second. A card that reads and writes at 150kb/s is sixty times slower than a card that reads and writes at 9mb/s.
Take a look at this web site and we can see the kinds of read and write speeds that people getting with their cards now days. The important thing that caught my eye was how widely the numbers vary. Looking at the chart I can see test results that range from 21mb/s all the way down to 3mb/s and less. That’s a HUGE difference!
In practical terms lets say we are dealing with a 4 gigabyte card that is full of photographs. A gigabyte is a thousand megabytes, so if your card is operating at 3mb/s it should take you about 22 minutes to get all of those photo’s onto your computer, probably a little more. But lets take that same data transfer of 4gb and do it at 21mb/s. That knocks your transfer time down to about 3 MINUTES! WOW!
Having discovered the wide disparity between the speeds of these cards I decided to see how my own cards were performing. I went to this web site and downloaded a card speed tester1. The results were not good, but at least I know now why I was so frustrated every time I needed to download pictures to my computer.
Can you guess how fast my cards transfer? I’ll give you a hint, its not 21mb/s, it’s not even 3mb/s. All of mine came out to less than 900kb/s! How bad is that? Remember that at 3mb/s it took more than 22 minutes to transfer 4gb, well at 900kb/s it would take about 74 MINUTES! Almost an hour and fifteen minutes! As I said above I don’t actually have 4gb cards as my camera only supports 2gb or smaller, but still, that’s 37 minutes per card. If you’re like me, and you can go out shooting and fill up two 2gb cards and part of a 1gb card, that is a LOT of time to wait to get your pictures on to your computer.
I paid about ten dollars each for my memory cards, and I thought I was getting a decent deal, but the days of cheap memory cards are over for me. Of course this means that my photography habit just got even a little bit more expensive than in already was. Long term I was planning on eventually trying to make a little money with my camera, but it looks like my habit could soon outstrip the profit potential of selling photographs. I may have to skip it and start selling easier products with a higher profit margin…… like cocaine or some thing. Do you think there are photography clubs in jail?
- 1 The program is Windows only and in German by default. Click the little button in the upper left to switch to english. The download link can also be difficult to find. Look for the blue link that says "Direct Download Of Software For version 1.4 of H2testw". It's just above the start of the comments.
- If you have a Mac you don't need to download anything. Open the Activity Monitor, Click on disk activity below the process list, and click on the data button below the moving graph. Then transfer a large file to the card and as it writes you can see the write speed to the left of the moving graph.