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How Important is the Speed of a Memory Card?

written by: Caroline Thompson•edited by: Rhonda Callow•updated: 11/23/2010

Choosing a memory card can be daunting with all the choices out there. There are different variables for each card and speed rating is one of those variables. Here is a simple breakdown of why speed is important in a memory card.

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    What is a Memory Card?

    There are many types of memory cards.

    • Compact Flash - Mostly used in professional DSLR cameras.
    • SDHC Cards - Cameras
    • Secure Digital - Memory cards for cameras, MP3 players, PDAs and cell phones. These cards have a switch that lock so data cannot be erased. This prevents the user from accidentally recording over data or from deleting data.
    • Memory Stick - Cameras
    • Gaming - Store games, video and pictures
    • Mobile - For mobile phones.
    • Video Cards - Video and HD video.

    Basically, memory cards store media. That includes text, video, games and images. Most memory cards are mass storage devices. Since they don't have any moving parts, they are great for portability, durability and reliability.

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    Memory Card Speeds

    With all digital media, image size is increasing. Images from cameras are getting larger with higher resolutions, video games are getting larger with more complex functions and better graphics and the same goes for other media that uses memory card technology to store the data. As the size of data increases, the memory card gets slower because of transfer rates. This is why manufacturers have stepped up and started producing larger capacity and higher speed memory cards. According to the Compact Flash Association, "The CF Specification can support capacities up to 137GB." Which means there is room for growth.

    Speed Rating

    Memory card speeds go from 6x all the way to 600x. Here is how to figure what this means in terms of data transfer. The base rate of data transfer is 150 KB/s (150 kilobytes per second). If the card speed is 133x, then the formula would be 133 x 150Kb = 1995000. So the data transfer rate of the card would be 19.95MB/s, or roughly 20MB per second of data transferred. Now you know how to figure the data transfer rate from the rating on the memory card.

    Read/Write Speeds

    Higher speed cards help improve the camera's performance by allowing higher write speeds.

    • Shooting in burst mode and continuous shooting mode - For the sports photographer this is a big plus. Catching fast action shots is the bread and butter of pro sports photographers.
    • Catching those spontaneous human moments - Whether it is at a family event or on a professional shoot, the ability to capture the moment and not have to wait for the image to write to the camera before taking another shot is worth the extra cost of the card.
    • Getting sequence shots - Taking a selection of images in sequence to show an action, such as in horse racing, marine mammals breaching the water, etc.
    • Response time in video games - As video games get more complex and have better graphics, the response time needs higher speed memory cards.
    • Shorter wait times - Being able to shoot without waiting for the images to write to the memory card. This is important in all photography and video applications.

    Higher speed cards also transfer data at faster rate.

    • Shorter download time - This means less waiting for the data to be transferred to the computer.
    • More time for editing - Less time downloading means more edit time.

    Basically, higher speeds allow for better data transfer rate, less wait time, faster download and larger images because the faster write speeds accommodate the larger image size.

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    A Word About Price

    Higher speed memory cards make life easier, but they come at a price. At the high end they can cost over $800. The cost of memory cards depends on several factors:

    • Type (CF, memory stick, etc.)
    • Storage Capacity (8GB, 16GB, 32GB, etc.)
    • Speed (20x, 40x, etc.)

    It pays to shop around. There are many manufacturers of memory cards and the competition between the brands gives the savvy shopper some real bargains.