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CF/SD/XQD Performance Database
Thursday, July 12, 2012 | by Rob Galbraith
The CF/SD/XQD Performance Database is a compilation of write and read speed test results designed to aid the serious amateur and professional photographer in selecting camera storage media for a Canon or Nikon digital SLR.

Write speed test results for each of the digital SLR models actively being tested, as well as card-to-computer transfer rates, can be accessed from the popup menu above.

Defining performance

A memory card is a critical component in the professional photographer's digital system. After all, it's the thing that holds the pictures. We hope that the CF/SD/XQD Performance Database will, first and foremost, enable you to determine which cards offer the speed your workflow requires. But we encourage you to look at card performance holistically. While speed is important, so is the warranty, tech support and reputation of the company whose name is on the label.

Though you may have come to this database to see how CompactFlash, SD/SDHC/SDXC and XQD cards perform in your camera, we think it's equally important these days to consider card-to-computer transfer rates. That's because in our own workflow, the time it takes for photos to transfer to the computer is often a bigger bottleneck that in-camera write speed. As both cards and card readers get faster, we expect that card-to-computer transfer speed will become even more significant a factor in the card selection process.

An introduction to CompactFlash and SD/SDHC/SDXC technology

There are two sizes of CompactFlash. They vary in their thickness. CompactFlash Type I (CF I) cards are 3.3mm thick; CompactFlash Type II (CF II) cards are 5.0mm thick.

side pins
CompactFlash Type II (left); CompactFlash Type I (right)

All of the CompactFlash-capable cameras in the database accept CF I, while a handful also accept CF II.

SD is short for Secure Digital, and there are three variants of it on the market: SD, SDHC and SDXC. The differences between the three are on the inside, as they are the identical physical size and have a similar connector arrangement. SD cards are limited to a maximum capacity of 2GB (there are a handful of 4GB SD cards out there, but they don't work in all cameras and card readers), while SDHC cards top out at 32GB. SDXC allows for higher capacity memory cards in this form factor. XQD is a new memory card format that entered the market in the first quarter of 2012.

Though there are a myriad of brands on the market, most larger-capacity CompactFlash and SD/SDHC/SDXC flash memory cards contain controllers from SanDisk, Lexar and a number of lesser known electronics companies: Hyperstone, KTC, Skymedi and SMI, to name a few.

Flash memory cards contain, in addition to a controller, several flash memory chips. Toshiba, SanDisk, Micron and Samsung are among the biggest flash memory chip suppliers (Toshiba and SanDisk are also partners in the manufacture of flash memory). Almost all the companies included in the database purchase flash from one or more of these companies (or use their own if they're an industry heavyweight like SanDisk), for inclusion in their products. The controller and the flash memory together determine the raw performance of the card.

To give you an idea of the number of players involved in the flash memory market, here are several excerpts from Lexar's 10-K filing on March 16, 2006 for the 2005 fiscal year:

[Excerpt 1] We compete with semiconductor companies that manufacture and sell flash memory chips or flash memory cards. These include Hynix, Infineon, Micron, Renesas, Samsung, SanDisk, ST Micro and Toshiba. Micron and Intel have recently formed a joint venture known as Intel Micron Flash Technologies. SanDisk and Toshiba jointly develop and manufacture both low-cost and high-performance flash memory through their Flash Vision joint venture.

[Excerpt 2] We also face significant competition from manufacturers or card assemblers and resellers that either resell flash cards purchased from others or assemble cards from controllers and flash memory chips purchased from companies such as Renesas, Samsung or Toshiba, into flash cards. These companies include Crucial, Dane-Elec, Delkin Devices, Feiya, Fuji, Hagiwara, Hama, Hewlett Packard, Data I/O, Infineon, Kingston, Kodak, M-Systems, Matsushita, Memorex, Memory Plus, Micron, PNY, PQI, Pretec, Ritek, Samsung, SanDisk, Silicon Storage Technology, SimpleTech, SMART Modular Technologies, Sony, TDK, Transcend, Viking InterWorks and many others.

[Excerpt 3] In addition, an increasing number of companies are manufacturing their own controllers, including Genesys, Hyperstone, Prolific, SanDisk, Sigmatel, Silicon Storage Technology, SMI, Solid State System, Sony and Zoran. Such companies either combine their controllers with flash memory from third parties to manufacture their own flash cards or sell their controllers to third parties who use them to assemble flash cards. Additionally, major semiconductor companies such as Infineon, Micron, Renesas, Samsung and Toshiba have also developed or are currently developing their own controllers that will likely compete with our controller and/or card sales.

[Excerpt 4] We also face competition from some manufacturers of traditional film products. Kodak and Fuji are the largest and best-known manufacturers of traditional film products. Fuji has entered the flash card market, but does not yet manufacture its own flash cards. In 2004, we entered into an agreement with Kodak to sell flash cards under the Kodak brand on a worldwide basis.

[Excerpt 5] Several companies, such as Cornice, IBM, and Matrix Semiconductor, which was acquired by SanDisk in 2005, have introduced competing technologies for use in digital cameras. These include products such as Digital Capture Technology and the MicroDrive.

Technical background

If a CompactFlash card is designed to hold data, then it's either a miniature hard drive or flash memory inside. Miniature hard drive cards have been around for a long time, at least in computer years: early digital field photographers (i.e.: those who were shooting digital in the early 90ís) will remember the 85MB Maxtor PC Card hard drive as being THE card to get. Miniature hard drives operate much like their larger counterparts: to write a photo, a tiny arm swings over a rotating platter, encoding small areas on the platter with zeros and ones as it goes. Today, hard drive-based cards, including the Hitachi Microdrive and Seagate's Photo Hard Drive, have mostly faded from the shelves of pro photo retailers and have long been surpassed in capacity, performance and price/GB by flash memory-based CompactFlash. There are no SD/SDHC/SDXC or XQD hard drive cards.

Memory cards work on an entirely different principle. Zeros and ones are stored in memory cells, instead of on a rotating platter. This kind of memory is similar to computer RAM. There is a key difference, however, between computer RAM and the memory chips used in digital camera cards: digital camera cards contain non-volatile RAM. That means photos aren't purged when the card is removed from the camera. Instead, memory cells remember if they contain zeros or ones until told otherwise.

This type of memory is called flash memory. Flash memory cards contain memory, obviously. The greater the number of memory chips, and the more densely packed each memory chip, the greater the capacity of the card. Card capacities have been increasing as flash memory manufacturers have devised new ways to shrink memory chips. As of early 2012, 64GB and even 128GB CompactFlash  and SDXC cards are readily available, while a 256GB CompactFlash card has been announced.

Both flash memory and rotating hard drive cards contain a controller. The controller determines how data is to be written to and read from the memory on the card. Whether a flash memory card or a card like the Hitachi Microdrive will be speedy or not with a given camera is determined as much as anything by the controller architecture. A card that is fastest with one camera isn't necessarily fastest with another, because of how the controller interacts with and exchanges data with the camera. The write speed test results are a testament to this.

The flash memory itself determines the maximum speed of flash memory cards, since no matter how efficient the camera-controller communication, data can't be transferred to the card any faster than the flash memory is capable of receiving it. Part of the price premium charged for certain fast flash memory cards reflects the extra cost of using the fastest available memory.

Similarly, the maximum speed of a rotating hard drive card is limited to how fast its head can drop data into tracks as it spins.

As is probably already apparent, flash memory cards contain no moving parts. This makes them extremely durable. I unintentionally proved this point years ago, when I accidentally dropped a Lexar Media 160MB card from my shirt pocket onto a cement driveway a full story below. The card was fine and I lost no photos. The Internet is also filled with stories of photographers accidentally running their flash memory cards through the washing machine and, after the cards were left to dry, discovering that they'd lost no pictures.

The durability of flash memory cards makes them an excellent choice for news and sports photography in particular, because they are the most likely to survive the bumps and bruises they will receive during their life.

Individual flash memory cells have a limited lifespan. That's the bad news. The good news is that their lifespan is usually measured in the many, many thousands of erase/write cycles, and that card controllers utilize an algorithm that balances the wear across the entire card's cells. CompactFlash and SD/SDHC/SDXC cards are designed to automatically and transparently map out memory cells that go bad, or in some cases when they reach a predefined limit.

The speediest memory cards generally use single level cell (SLC) memory (SanDisk calls this binary-type memory). This type of flash memory also offers the highest number of erase/write cycles. The alternative is multi level cell (MLC) memory, which is slower and less expensive per MB than SLC, which in turn translates into lower-priced cards, but also a lower erase/write cycle specification. In recent times, controller improvements have meant that even some high-performance memory cards use MLC.

Regardless of whether a card contains SLC or MLC memory, it's designed to keep on working even after a few cells have expired, and even a busy photographer's flash memory card won't start turning off a significant number of memory cells until after many years of service.

Cameras don't write their stream of zeros and ones randomly. All digital SLR and compact cameras we've tested use the FAT file system as the basis for placing photos on a card and keeping track of the location of those photos. This means the cards themselves have to be FAT-formatted, regardless of whether they have a hard drive or flash memory inside. CompactFlash cards with capacities over 2GB must be formatted FAT32, a flavour of the FAT file system that is not widely supported in older digital cameras (though camera models introduced from roughly 2003 onwards should be FAT32-capable). 64GB and higher SDXC cards use exFAT, another FAT file system variant; while some several-year-old cameras will accept SDXC, they re-format them as FAT32 and are therefore officially not SDXC-compatible.

Testing notes

Prior to testing, each card is overwritten with zeros (a technique often called securing erasing), then reformatted in the camera, to ensure that corrupt formatting doesn't impact test results. Results are spot-checked with the cards "dirty" (filled with images, then in-camera formatted only), to ensure that write speed doesn't drop appreciably with any one card. Several years ago, a dirty or partially-filled card would often be much slower than one that had been secure erased and reformatted just prior to use. That's rarely true anymore.

The cameras are configured with default image processing settings (well, not necessarily the manufacturer's defaults, but ones that we've determined to be sensible for a given SLR), at ISO 800. The same test target, illuminated by the same light source, is photographed for all tests. All testing is done with fresh batteries. Results are averaged from three cycles each of the selected file format.

More information on testing procedures is found on the individual camera and other testing pages.

How can I be sure the card I buy is the same as tested in this database?

This is an important question, since the companies whose products are featured in this database are free to change the components in their memory cards at any time. Outfits that source cards from another manufacturer may change manufacturers several times a year, or even draw from several manufacturers simultaneously. And unless the model name or some obvious identifying feature of the card changes too, it can be difficult to know whether the card you select is substantially similar to the card tested here.

Fortunately, some CompactFlash and SD/SDHC/SDXC makers place a unique identifier on the card - a card series number, for instance - that is a reliable descriptor of the key components in the card, as long as you know how to interpret the identifier. Unfortunately, not all companies incorporate a unique identifier, including some that should, so matching a card in your hand to one in this database with 100% certainty won't be possible with some brands.

Here are some tips to help you determine if what you're buying is comparable to what we tested.

Look at the edge stamp Lexar, SanDisk and others stamp or engrave a series number onto the edge of the card. The photo below shows the edge stamp from an older Lexar CompactFlash card.

card side
Edge stamp

Look at the label Some companies attach a label to the card that contains the series number, or print it right on the main label.

serial number


Look at the internal information

power off

If you have a Mac laptop with a PC Card or ExpressCard slot, you can easily take a peek at some of a CompactFlash card's internal information. The operating system will show two fields of data (as shown above) when the CompactFlash card is in an adapter inside the computer and you click on the adapter's icon in the menu bar. Similarly, part of this information can be viewed in the Info window of Disk Utility, if the CompactFlash card is in a FireWire card reader.

If you have a Windows laptop you can do much the same: with a CompactFlash card in a PC Card adapter inside the computer's PC Card slot, right-click on the card's drive letter (or any drive letter in fact), click on the CompactFlash card name and then choose Properties. You'll see some information there, but there's more a few mouse clicks further: click the the Properties button, followed by the Details tab, then choose, in turn, Friendly name and Parent from the Property popup menu. (This may also work with ExpressCard adapters in compatible Windows laptops, but we haven't tried this yet.)

With any type of reader, you will also see some identifying information for CompactFlash in the file setupapi.log in the WINDOWS directory on the C: drive of a typical Windows XP installation. Here's an example setupapi.log entry for a CompactFlash card that uses Toshiba components:

#I124 Doing copy-only install of "USBSTOR\DISK&VEN_TOSHIBA&PROD_THNCF1G02CA&REV_3.00\1B03010305F416A9&0".

And finally, if you're paying attention when a CompactFlash card is being used on a given Windows XP or Vista system for the first time, you may see identifying information appear briefly in the configuration balloon.

If decoding card identifiers sounds like too much work, we agree. Until such time as all card manufacturers make it easier to identify what's inside the card, this sort of detective work will at times be a necessity.

Note that none of the above works to ferret out internal identifying information from an SD/SDHC/SDXC or XQD card. We don't know of a way to view meaningful internal data with this card type.

Beware of counterfeit cards Knockoff flash memory - CompactFlash and SD/SDHC/SDXC cards that appear to be from a major player (SanDisk is the brand that seems to be most widely counterfeited), but are actually knockoffs with labeling and packaging that closely mimics if not matches the real thing - is widely available on the Web these days.

If the deal seems too good to be true it probably is. We strongly recommend that you buy from a reputable retailer to minimize your chances of getting stuck with a fake, one that probably won't have the performance, reliability, compatibility or even the capacity of the brand and model you thought you were buying.

CF/SD Performance Database testing assisted by Megan Somerville.

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