Holiday 2012: Memory Cards


Memory cards are the standard devices for recording your images to when using a digital camera. They are descendents of film in a way, and are the medium in which your imagery sits before viewing. They differ from film, of course, in that they are flash storage devices, similar in idea to external hard drives that are used with computers. Memory cards permit re-recording and overwriting so as to allow infinite use, and do not require dedicated power sources to store or contain data.

What are the basic memory card formats?

Memory cards are available in a variety of shapes, sizes, capacities, speeds, and so on. The most important and first rule to follow is to purchase a memory card that is compatible with your device. Most cameras are compatible with CompactFlash (CF), Secure Digital (SD), or Memory Stick style cards, although other types do exist (such as miniSD, microSD, XD, and XQD). Consult your manual or check your camera to see which type or formats are accepted. Once the general format has been determined, you can then begin to consider the different types and features that are offered.

Recently, and especially in professional-grade cameras, dual memory card slots have been integrated into the design allowing you to use up to two memory cards at a time. The most common combinations are two SD slots, one CF and one SD slot, or one Memory Stick and one SD slot. Another combination, which is currently only featured on the Nikon D4, is having one CF card slot and one slot to accept the newly introduced XQD memory card.

Which memory card capacity is best for me?

Expanding on the memory card format, cards come in different capacities ranging from as little 1GB up to 256GB. A card’s capacity is fairly self-explanatory, though it should be noted that not all cameras support card capacities over a certain limit. Even though there are memory cards available in capacities up to 256GB, many entry-level and intermediate-grade cameras cannot support these cards. Before assuming it is best to buy a card with the greatest amount of space, make sure you are working within your camera’s limits. Another note regarding using cards with such great capacity is that it is often preferred to have several small-capacity cards rather than one large-capacity card. Splitting the amount of memory you bring with you across numerous cards gives you the versatility to use individual cards for different tasks. For instance, if traveling, you can use one card per day to keep a succinct and orderly record of which day’s photographs are on which card. On the other hand, if working with HD video or other shooting-intensive applications, a large-capacity card might suit you better so you can avoid running out of space and having to switch cards as often.

Another consideration when deciding upon card capacities is the type of files you generally shoot, and how large your average file size is. If you are working with a small 12 megapixel point-and-shoot camera and only shooting JPEG files, you can record upwards of 8,000 images to a single 32GB memory card. But if you are working with a full-frame DSLR and recording both RAW and JPEG file types simultaneously, you might only get 500 or so images per 32GB memory card.

Are memory card speeds and classes important?

Another determinant for choosing a memory card is how fast its read and write speeds are. This, again, is dependent on your shooting needs and the camera you are using. The exception in this case is that higher numbers are always “better;” whether or not you actually need a card to read and write a file at 150MB per second is a different question. When looking at different memory cards, there will often be two numbers shown: read and write speed. Write speed refers to the transfer rate, in MB per second, that the card can receive files from the camera. The higher the number, the faster images can be recorded. Read speed is similar; however, this rate, also measured in MB per second, refers to how quickly images can be transferred from your card to your computer.

Higher write speeds enable faster continuous capture with minimal backup times. Faster read speeds enable quicker transfer times from your card to your computer for importing images. Higher performance cards are more essential for video recording, as more data is being continuously written to your cards, versus shooting single, still images. Some memory cards will also display these speeds in terms of "x" (such as 400x or 1000x).  This "x" is the multiplication of a standard data-transfer rate of a CD-ROM drive, and a simple formula is that 1x=150KB/s; therefore a 400x memory card can transfer data at a rate of 60MB/s (400 x 150 = 60,000 / 1000 = 60).

Additionally, memory cards can be broken down into different classes or ratings, and these differ depending on memory card format:

SD Cards

SD is more of a catch-all term for the shape and size of this format memory card. A true SD card is becoming more and more obsolete with the advent of SDHC and SDXC cards. The difference in these cards is their maximum capacity: standard SD cards have a maximum capacity of 2GB; SDHC cards have a capacity greater than 2GB but less than 32GB; and SDXC cards are greater than 32GB and up to a theoretical limit of 2TB, although the current largest SDXC card is 256GB. Furthermore, SD card types are divided into speed classes.  These classes are based on a minimum sustained data writing speed (with the maximum write speed often surpassing this number by quite a lot). Class 4 equates to a minimum 4MB/s sustained write speed while Class 10 means a minimum 10MB/s write speed.

There is also a UHS (Ultra High Speed) Speed Class. The current standard for this is UHS-I, or UHS Speed Class 1. UHS-I cards have a minimum write speed of 10MB/s, like a Class 10 card, but support the UHS bus interface for a higher potential of recording real-time broadcasts and larger HD video file sizes. As with general read and write speeds, these speed classes, or minimum sustained write speeds, relate to better performance—the higher the number is. However, these numbers are mainly used as a reference tool for video recording since it is a continuously recorded medium. Depending on the rate at which your camera can record video, you should select a card that meets or outperforms this number to ensure clear, fluid recordings.

These classes and standardizations are also applicable to microSD and miniSD cards; however, such cards are physically smaller in size and are often used in smaller devices, such as cellular telephones. These cards can also be adapted through the use of a standard SD-size passive adapter to function in devices that only accept SD-sized cards. The other difference these smaller cards have is the lack of a physical write-lock switch on the exterior of the card, that would otherwise permit manual locking of the card, similar to the write-protection tab of a VHS cassette.

CF Cards

Similar to SD cards, CF cards also have a class system; however, it is not quite as extensive as the division between different classes and designations. Older CF cards utilized a communication protocol called PIO (Programmed Input/Output). This protocol was divided into modes depending on the theoretical performance of a given card. Mode 6, the highest level, allowed a maximum transfer rate of 25MB/s. More recently, CF cards have adopted a new method of communication called UDMA (Ultra Direct Memory Access). UDMA cards are also divided into modes, with the lowest, Mode 1, permitting up to 25MB/s and the current highest, Mode 7, permitting transfer rates up to 166MB/s. As with SD cards, the higher the number, the better the performance for intensive imaging tasks such as video recording or continuous shooting.

Memory Stick Cards

Memory Stick PRO Duo cards are a proprietary memory type used in many Sony devices. These cards are similar in size to SD cards and are smaller than the original incarnations of the Sony Memory Stick. Currently, only two types of Memory Sticks are available, either the Memory Stick PRO Duo or the Memory Stick PRO-HG Duo. The PRO-HG Duo is the faster of the two types, offering approximately four times faster performance over the PRO Duo.

XQD Cards

The newest type of memory card that is currently being used is the XQD card. This format is designed for more contemporary means of image production, including HD video recording and continuous high-resolution image capture. XQD cards are currently available in two classes: the standard XQD and the XQD S-series. The standard class supports transfer speeds up to 125 MB/s while the S-series supports up to 168 MB/s. The XQD memory card type has a theoretical capacity limit greater than 2TB, although currently the largest capacity card offered is 64GB. The Nikon D4 DSLR is the first camera to support the use of XQD card types.

What happens if the data from my memory card is lost?

While memory cards are generally thought of as a secure and dependable means for storing images and data, there are times when they can fail and result in a loss of your imagery. This is similar to computer drives crashing, and just the same, it is always a good idea to keep a consistent and orderly backup of your files. If a memory card fails before you have the chance to back up its data, there are programs available to help you recover lost files. These programs, which are often included with the purchase of a memory card, work to scour the memory card’s lingering data to piece together any files that may have become corrupt, lost, or even deleted.

When you delete an image from a memory card, it is often never fully deleted immediately; this is a good thing. It isn’t until you format your card that traces of an image file are completely erased. Because of this, tools like SanDisk’s RescuePRO and Lexar’s Image Rescue 4 can piece together files that are not easily read by your camera or even by your computer when simply viewing the contents of the card. These programs utilize complex algorithms to scan and recover all types of data, including image files as well as other document types.

When working with these tools, it is best to use an external card reader and an external hard drive to promote a more secure means of transferring recovered data. These programs usually have an intuitive interface that allows you to visually scan through recovered data and select the files you wish to save to a more secure place. Once you have recovered all of the data you need or that is possible, it is best to then completely re-format your memory card to lessen the likelihood of any future crashes or failures due to any lingering peculiar data structures.

What is the best way to transfer images and data from my memory card
to my computer?

Transferring data between your computer and your memory card can be accomplished in a couple of ways: either by connecting your camera to your computer with a cable, or through the use of a dedicated card reader. A memory card reader is the preferred method for moving your data between card and computer, due to its versatility and the simple fact that when you use your camera as a card reader, you are asking the camera battery to do additional work. Additionally, card readers often feature ports to accept several kinds of memory cards for greater versatility when working with multiple cameras or card formats. Dedicated card readers are bus-powered and connect directly to your computer, usually via a USB 2.0 or 3.0 interface. USB 3.0 memory card readers permit faster transfer speeds due to the 3.0 specification, and they are all backwards compatible with USB 2.0 ports for devices without USB 3.0 compatibility.

What is an efficient way to keep my memory cards organized?

Part of memory cards' appeal is how small they are in comparison to some external hard drives and other storage formats. When traveling, it is much more feasible to carry several memory cards than only one or two cards and a computer to facilitate offloading images from your cards. This small form factor can also be an issue, though, because it is easy to misplace or mix up such small items with other similar cards. An ideal solution is to use a memory card case when traveling, or for storage at home. These small cases provide a dedicated location for keeping certain sized memory cards, and offer protection from crushing, impacts or weather.  Additionally, cases are available to hold several different kinds of media or memory card formats.

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This article is very interesting and educational, but it doesn't answer the question every reader will want to ask: Which are the best brands in terms of performance and reliability? The e-mail blast which linked to this article says "A memory card is a memory card: Really?", which just begs the question: which ones are the best?

Any suggestions on websites that would rate the various brands?

Memory cards vary in terms of the amount of data they will hold and the speed at which they can move data on and off the card. Manufacturers will usually list their spec'd speeds in a particular cards description or specifications. Rob Galbraith runs an independent web site dedicated to testing the performance of currently available memory cards and DSLR cameras combinations.

I wish to thank the above authors, all the above. This set of comments has not only taught me what I needed to know on the subject--Cards, in my case CF--but is done like a group of intelligent humans conversing to share what they both don't know the answer to and DO. Thank you all, I do get so tired of the jerks that seem to swamp the internet.

Again, Thank you


The fastest and most durable flash memory cards (lasting ~1 million or more read/write cycles per bit) are built using SLC (single-level cell) flash technology. Those built with MLC (multi-level cell) technology provide denser, slower, not-as-long-lasting (100K, 200K write cycles) storage -- but it is less expensive and should still last a lot longer than most camera bodies.

Unfortunately, flash card manufacturers don't label their cards with the underlying technology used in them. You can probably find out on the manufacturer's web site, with some searching around.

Most manufacturers have a line of memory cards that's considered their "Pro" line -- that one usually uses SLC technology. The more consumer-grade flash cards generally use MLC technology.

Others are guaranteed to have other opinions but, IMHO, given that an MLC flash will outlast the lifetime of all but high-end pro camera bodies, there's no reason to by SLC for its longevity. So the only reason to buy SLC flash is if you need extreme write speeds.

Regarding flash reliabilty, I've owned probably a dozen CompactFlash cards for my DSLRs and my family has owned probably that many SD or SDHC cards for their cameras. I've only ONCE had a failure (card wouldn't read in the computer) -- and that was a card from one of the top two "Pro" brands, I was able to recover the photos using data-recovery software, and the error cleared up after reformatting (so probably was not a hard flash-card issue). So in 12 years, I have never had a "hard" flash memory failure, and I have not seen the top brands (e.g. Lexar and Sandisk) show any higher reliability than any other brand.

So I suggest that you get cards that are fast enough for your needs (faster write speeds driven by continuous shooting or video capture) and look for a good price. Pay attention to brand only if you're a pro and want the more stringent guarantees offered by the "pro" lines of flash cards, or need a card that's guaranteed sealed against quite extreme environmental conditions (e.g. water submersion or extremes of temperature) that few of us encounter.

I do avoid total no-name flash brands, although have no proof that they're any less reliable than others.

good info - thanks - in 12 years of digital photography - i just had my first card failure - ouch - but the recovery software saved the day and found my images
i always use a few cards for a wedding etc
and change them out every 50 to 100 images - just for safety
for me - a nikon d 300
the clue was that there was a problem was that the post view image was blank on the camera back

Memory cards vary in terms of the amount of data they will hold and the speed at which they can move data on and off the card. Manufacturers will usually list their spec'd speeds in a particular cards description or specifications. Rob Galbraith runs an independent web site dedicated to testing the performance of currently available memory cards and DSLR cameras combinations.

I would agree - I'd like to know which cards have lower failure rates. Which card types are best for stability, speed, low cost, high cost, etc. Which brands are just re-branded (stickered)? Which cards are different manufacturers, etc, etc. Which manufacturers have better quality checks, warranties, etc, etc.

The real questions we want answered are is the $25 SD card at Sears just as good as the $8 one at Walmart. Is Lexar the entry level card, or pro-level card? What are the differences between Pro and uber cheap.


Very good points and also begs the questions, of each type which are among the top B&H best sellers, have the fewest returns, receive most favorable reviews?

Thank you B & H for this memory card primer. It is well written and balanced. One cannot expect you, the retailer, to promote one brand over another.

I think this was extremely well written. I have a couple more tips..... I teach on location in the US and Europe and am used to traveling with my equipment. Coming from the professional side before being a teacher, I know how important back-up is for success. I bring a small external hard drive with me now to load my cards into on the road. That way I come home with my images in two places. Both are with me as carry-on. I do not usually like to carry the extra weight of a laptop for downloading and since I am teaching, there is never time to work on my images. The other tip is that I only use one card per day and then that cart goes into my suitcase at the hotel. I do not carry around more than one days worth of images at a time. I store my used cards in the wildest colored zippered cosmetic bag that I have so I can find it really easily in my suitcase since most of my clothes are black. Ladies know this...we get dozens of these little bags for free over time. Some of them are really loud and ugly....that is the one I choose to use. My external hard drive is in there too. I know where my used cards are at all times.

I am interested to know how you transfer to a hard drive without a laptop? is there a particular model you use? or can recommend


A hard drive is a computer peripheral which on its own cannot save any data. It like a printer or scanner requires instructions or drivers to tell it what to do. Portable storage devices are available which have HD's inside to save or back up your data files. They mostly vary in storage size, compatable memory cards and viewing screen options.

Portable Data Storage

It is widely reported in user product reviews that many SD cards do not come close to meeting the specs under which they are sold, such as class 4 or class 10 write speeds. It would be very valuable to know whether this is true, and if so, which manufacturers are lying and which are telling the truth.

A very comprehensive article.

For the same capacity, why are CF so much more expensive than SD cards? Besides price is there an advantage of one type over the other?


There maybe some manufacturing costs but I think the main issue is the industry moving slowly away from CF cards (the recently released Canon 6D and Nikon D600 take SD memory)and are centering on SD,SDHC & SDXC/UHS options.

We have not found SD memory to be any more or less fragile than any other card format. The Achilles' Heel of CF cards was lining up the pins when inserting the card into a camera or reader. I've heard many a horror story of a card incorrectly inserted into a slot crushing pins and requiring costly repairs.

Standard SD memory was limited to 2gbs although some 4 gig cards were available.

SDHC (High Capacity) were formatted with the FAT32 file system and are available from 4 GB's to 32 GB's.

SDXC (eXtended Capacity) format supports cards up to 2 TB (2048 GB), compared to a limit of 32 GB for SDHC cards.

UHS stands for “Ultra High Speed” and refers to a format that allows higher bus interface speeds on Secure Digital High Capacity (SDHC) and Secure Digital Extended Capacity (SDXC) cards. UHS-I defines interface speeds up to 104MB/sec. Current HD video cameras benefit from these cards for recording HD video.

Most CF cards are much faster than most SD cards. The SD cards that are just as fast as some CF cards are also more expensive than the more popular, slower ones. A Class 10 SD card must be able to write 10MB/sec. An UDMA Mode 7 CF card is rated for 166MB/sec. Even an UDMA 1 card is rated at 25MB/s.

A very good, balanced and comprehensive article. The explanations dealing with card categories/ratings helps one keep up with the rapidly evolving technologies and applicable applications.

Looking for some answers ?

Please tell me if the Lexar Professional 800x 32GB UDMA 7 CompactFlash Memory Card is compatible with my Nikon D700 DSLR camera

Yours truly,
Michel Villeneuve


Manufacturers rarely test every available memory card and with the D700 going out of production, I doubt they will continue. Officially, Nikon supports the Lexar Professional UDMA 300X (8GB,4GB & 2GB).

They also add:

"Other cards have not been tested but may work."

"64GB memory cards may be used with the latest firmware update."

I see no reason why the card would not work. You may not be able to take advantage of the cards top data transfer speeds but should not have significant issues in use.