Digital Camera Memory Cards Explained

memory cards

Digital Camera Memory Cards

Buying a memory card is usually the first item purchased for your new digital SLR camera. Purchasing a card may seem like a very easy procedure. But that will change once you start researching them. You will see that you have a lot of options ranging from $4.00 to $700.00. With such a wide price range, there is more involved than the card manufacturers just trying to make more of a profit.

With a little bit of research involving the technology involved, you will be sure that you are getting the correct memory card for your digital camera and not wasting too much cash on something that doesn’t make any difference.

SD (Secure Digital)

What has become to be the more popular type of memory card utilized for digital cameras today is the SD (Secure Digital) card. This card is designed for a lot of hardware such as cell phones, digital cameras, PDA devices, and video cameras. More computers and TVs are being built with SD drives installed. There are 3 different sizes of SD cards; the SD card which is about the size of a postage stamp, the Mini SD Card which is a smaller, and the tiniest of the three, the Micro SD Card which is mostly used for cellular phones and smaller pieces of equipment.

The SD Memory Card is compatible with a lot of DSLR cameras as well as most digital point and shoot cameras. It can be bought to contain up to 2GB of storage. The SD Card was created in 1999. These memory cards can be found at inexpensive prices. The more recent designed memory cards that are explained next have more capacity as well as quicker data writing speeds and transfer rates. Even though you can get these memory cards at a capacity of 2GB for as low as $5.00, I do not advise purchasing SD Cards. For $5.00 more you can buy a 4GB SDHC (high capacity) card. The extra storage and speed that you receive for the price is worth it, especially with the higher resolution, quicker cameras and video capable DSLRs being built now. If you run a search on Amazon for an SD Card, the majority of the hits will be for SDHC cards. A fast way to see the difference is to check out the capacity. If the memory card is 4GB or more, it is a SDHC card, and 2GB or less is a SD card.

The SDHC (Secure Digital High Capacity) memory card is the next generation for the SD Card. The SDHC memory card is the same shape and size as an SD card, but it has higher transfer rates and more storage capacity. Most cameras that are being built now are SDHC compatible. Most hardware that is compatible with SDHC cards are backwards compatible with SD cards. It is possible to buy SDHC memory cards that have the ability to store 4GB to 32GB. They make SDHC cards for as low as $7.00. I advise thinking about the storage you need, or may need. It doesn’t hurt to have more than you need and for the cost it is not a bad idea to get more. A 16GB memory card will cost around $36.00 where as an 8GB about $20.00. If you record a lot of video or tend not to upload your pictures immediately after all events, then you may want more capacity. But another important factor when buying a card is transfer rates or the speed of the card. See Speed below.

The SDXC is the newest generation of memory card from the SD Association that increases storage from 32GB to 2TB. The SDXC’s physical dimensions are equal to the SD/SDHC cards. The only difference is on the insides. Most cameras being manufactured today, are going to be built with SDXC compatibility. This ups the storage and speed limits from the SDHC card. Consider that you will pay top dollar for new technology and their will be things to consider before paying top dollar for the newest cards. If you purchase one of the new DSLR cameras available now, you may want to consider a highly rated SDHC card for the first few months then transition up when costs decrease. This will allow time for the SDXC cards to be tested so that research can be done to see if the upgrade is even worth the money for your digital camera.

Based on the SD Card Association’s website there are three speed classes of of SD/SD/SDHC cards (Class 2, 4, and 6). Class 2 SD cards have a minimum transfer rate of 2 MB per second, class 4 have 4 MB/s and class 6 has 6 MB/s. There are class 10 cards available too. The new SDXC cards coming out will be capable of transfer rates of 109 MB/s with possible capabilities of 300MB/s in the future. Manufacturers do increase the transfer rates higher than minimum. A class 6 card can be made to so that transfer rates of 12 MB/s are possible. It is important to read the manufactures explanation of the memory card. Generally speaking, the quicker and more capacity means more cost. Another fact is that just because the builder says that the card can transfer at 12 MB/s doesn’t mean that YOUR digital camera will be able to produce such results. See “Speed”.

CF Cards (Compact Flash)

The CF (CompactFlash) memory cards are bigger in size than the SD memory cards mentioned earlier. They come in two types, CF type I and CF type II. Type II cards are about 2 millimeters thicker than type I memory cards so it is important to check your camera’s compatibility before buying a CF card. Many digital cameras that allow CF cards allow both types, but newer digital cameras manufactured today seem to be allowing only the type I memory cards.

The CF memory cards are a little advanced over the SD cards when it comes to size and speed. Sandisk recently manufactured a 64GB CF-I card that has a transfer speed of 90 MB/s. But this is going to cost you anywhere from $300 to $600. Though the new SDXC explained earlier has abilities of 2 TB of storage and up to 300 MB/s transfer rate (by the end of 2010), they are not available for purchase yet. And when they are, they will be in the 64GB range and cost about $600.00 too. So, if you need the MOST space and speed then a CF card will hand that to you, but for a big price. Also it will most likely out perform your camera leaving you little difference to notice from a slower SDHC memory card.

UDMA – The 64 GB CD memory card talked about earlier has UDMA technology. When looking for a digital camera you might see this as a highlight for the camera in the “storage” category. UDMA (Ultra Direct Memory Access) is a more recent technology that speeds up the movement of data. This technology is only available on CF cards. But not all CF memory cards are UDMA compliant. It is necessary to keep in mind that before you spend extra cash on a CF UDMA card be sure that it will work with your camera. If your digital camera doesn’t support UDMA, it will probably work O.K. but you will not see any increase in performance. A huge benefit of UDMA is the transfer speed to your computer. But you will not see improvement in performance unless you have a UDMA enabled memory card reader.

FAT32 – When looking for a digital camera, you might see “FAT32 Enabled” in the storage description. If you are looking at cameras now and you notice this, it might be because you are considering at a digital camera that was designed a while ago but is still being built today. FAT32 is a file system that took over the old file system which was used by digital cameras and memory cards (FAT or FAT16). Once the limit of the memory cards broke the 2GB wall the necessity for a more efficient file system was noticed. The FAT32 system is more efficient allowing mass storage up to the levels needed today. So a FAT32 is no longer a feature that needs to be boasted as an attractant for consumers, because all digital cameras being built now are FAT32 compliant.

Sony Memory Stick Pro Duo

The Memory Stick Pro Duo is a memory card developed by Sony. It is one of the latest versions of the Sony Memory Stick. If you are thinking of buying a Sony DSLR you might have observed that it is a choice to use for storage of your pictures. Sony is the developer of the card so it only makes sense that they have a slot for it on their cameras. They MemoryStick Pro Duo can be bought up to 32GB with a transfer rate of up to 36 MB/s. They cost more than the SDHC cards. The Sony DSLR models have dual slots for memory cards. You can use both a Sony Memory Stick Pro Duo or a CF memory card in the A850. In all other Sony DSLRs you have the choice between a Pro Duo or an SD/SDHC.


The speed of the card is as important as the space. The question when it comes to speed is; How important is speed to your photo shoots? If you shoot a lot of sport photography or children playing and like to use the burst feature on your DSLR, then the transfer rate is something to be considered. The transfer rate is the rate at which the memory card can write data from the camera. The camera has a rate at which it is able to move data to the memory card too. You need to consider both. If your camera is only capable of moving data at 7 MB/s, then buying a memory card that has the capability to move data at 30 MB/s is not logical. Knowing how the transfer rate works with a particular piece of hardware can allow you save cash by not purchasing a card that was designed for a quicker camera.

For example; the Nikon D3000 boasts a burst rate of 3 frames per second. Also the D3000 has a buffer of 100 frames. The buffer is a temporary holding spot for the pictures in the camera’s memory prior to it being transferred to the memory card. The camera is able to write to it’s own memory quicker than to the card, so this enables you to take the subsequent shot fast instead of waiting for the transfer to finish. Beings that the camera’s image processor itself restricts the camera to 3 frames per second, a quicker card will not improve this performance. And since the buffer can carry 100 frames, you most likely don’t need to worry about going over the limit.

However, this only applies to jpeg files. If you own a Nikon D3000 and decide to shoot NEF (RAW) files, the buffer allows 6 frames to be stored before you are restricted by the transfer rate of the card. Once the buffer is maxed out, your rate is dependent on how fast the camera and memory card work together to transfer the files onto the card. If you burst those first 6 frames, you will get 3 frames per second for 2 seconds but then the burst rate will decrease a lot depending on the transfer rates of the camera and card. So if you own a D3000, and you want to shoot RAW files and you know you will need to burst more than 6 shots at a time, then you will need to invest in the fastest card for your camera. Where as if you know that you are going to shoot jpeg all the time or you know that you don’t need burst speeds that continue over 6 shots, you can keep some cash and buy a slower card without noticing any lack of performance.


Though I think transfer rate is equally important, storage space seems to be the biggest priority for memory card buyers. If you research a card manufacturer’s website, you will notice a lot of charts showing how many images and minutes of high def video each size memory card can hold. You need to think of your mission as a photographer.

I prefer to have some back up. I would like to have 2 or 3 cards with me that have the capability of holding 500 RAW pictures a piece, instead of 1 that can hold 1000. These solid state memory cards are very strong. They can handle being dropped, stepped on and there are stories that many have survived being submersed in water for a day as well as a cycle through the washing machine with no data lost. But you can’t recover lost images from a lost card. So I advise carrying extras with you. Shooting RAW uses more space over jpeg. But just because you take jpeg images now doesn’t mean you won’t start shooting RAW in the future. Also, just because you are not utilizing your memory card for video now does not mean you will not buy a new HD Video Camera nest month. With storage costing so little today, I advise paying the extra $10 or $25 for more capacity. This allows you to use the card for longer and maybe other pieces of hardware. Regardless, using a DSLR, with the burst rates they are capable of, I do not advise getting a card that will hold less than 500 images.

Visit my site to see a chart that gives some examples of how many images a particular card will hold depending on the setting of the camera. The more megapixels, the less images. Also if you are taking RAW pics you can expect the quantity of photos that can fit on the memory card to be reduced by more than half.

About the Author
This articles was written by Joe Watson from lrcamera dot com. “I practice photography as a hobby. I love to learn and write what I learn. I hope this helps anyone out there with a new DSLR camera.”

Like This Article?

Don't Miss The Next One!

Join over 100,000 photographers of all experience levels who receive our free photography tips and articles to stay current:

4 responses to “Digital Camera Memory Cards Explained”

  1. paul says:

    my camera comes up with right protected on my card so I bought a new one and that says the same, can anyone explain why.

  2. coolphotographer says:

    the button on the side is a “lock” it keeps you from deleting any of the pictures on the card

  3. Tina says:

    Could you explain what the little white plastic button on the left side of the memory card is for exactly,
    and why its there?

  4. swaminath says:

    great blog!!! thanks.

    so if the speed of my SD memory card is slow. it may kinder my cameras performance also right?

Leave a Reply

Your email address will not be published. Required fields are marked *