What to take into account when choosing an SD card?

Many times we tend to think that all Secure Digital memory cards are the same, basing our purchasing decision solely on price. But are we sure to trust a single recording to any medium? What parameters should be considered before opting for a card? What relationship does capacity have with speed? In case of disaster, how can we recover our data?….

Secure Digital (SD) is a storage device that preserves information even with power loss, that is, it is a non-volatile memory. Initially developed back in 2005 by Matsushita (Panasonic), this memory card format is used today in countless consumer and professional devices of the highest demands.

Many times we tend to think that all Secure Digital memory cards are the same, basing our purchasing decision solely on price. But are we sure to trust a single recording to any medium? In a market with increasing competition every day, not everything is a matter of price but the reliability and durability of the support are factors to take into account in critical jobs such as video capture and storage.

Although Compact Flash cards, with better features but larger size, burst into the professional market, in terms of non-proprietary and exclusive recording media, the Secure Digital (SD) format has ended up prevailing in all types of consumer devices, and very widely in the professional market.

SDs took their first steps with capacities that were barely around 16, 32 or 64 MB. However, just one year later, in 2006, 8 GB was reached and in 2007, 16 GB. And when everyone thought that this type of solid state memory had reached its ceiling, we found that today we have storage options on the market that reach up to 2 TB.

In this way, in less than a decade we have gone from the first SD (Secure Digital) with capacities of just 2 GB to Secure Digital High Capacity (SDHC) and the new generation Secure Digital eXtended Capacity (SDXC) with capacities of up to 2 TB on a tiny card.

What information does the support provide us?

All cards have printed information that the professional will find very useful to choose a reliable support according to the use they are going to give it. The cards are clearly identified with the type of card (SD, SDHC or SDXC), its capacity, maximum speed (the higher the speed, the faster the images are stored) and Video Class speed (minimum speed).

Most manufacturers print only the read speed (higher than the write speed) on their cards.

Generally, we tend to focus only on capacity, but what about access speed? In professional environments it is a parameter to take into account since even if a warehouse is very large, if its access door is very small, filling it or removing things from it will become a real torture and a waste of time, which in most jobs is a key factor.

MB/s vs. “X” speed

On most cards we find information that a priori may be very cryptic but that provides significant information: “the X”. What is that X that we find on the cards? Assuming that the speed of a CD is 150 kb/s or 15 MB/s, we can know how many “X times” our support will be faster.

Some manufacturers only publish the speed of their cards using the 'X' guidelines, often taking advantage of the user's lack of knowledge. However, leading manufacturers of this type of cards, such as SanDisk, clearly specifies on its media both the 'X' and the speed expressed in MB/s.

So, this would be the speed equivalence “X times” in relation to MB/s:

• 133x = 20MB/s
• 200x = 30MB/s
• 300x = 45MB/s
• 400x = 60MBs
• 600x = 90MB/s
• 633x = 95MB/s
• 667 = 100MB/s (666.66x)

Question of classes

There are classes in everything, and in the sometimes intricate world of cards it was not going to be any less. In many of these supports we find the Class video speed. What is this? Class video speed does not have to determine a purchase, being an incorrect measurement on which to base a purchasing decision if it is unknown what use the media will be given.

Each SDHC card has an associated class whose classification has been defined by the SD Card Association as an indicator when assessing the guaranteed sustained data transfer rate of a given card.

Currently, the minimum guaranteed transfer speeds guaranteed by the cards have been standardized with the following nomenclatures:

• C2: Guaranteed sustained data transfer rate of 2 MBPS of information
• C4: 4 MBPS
• C6: 6 MBPS
• C10: 10 MBPS

In video production, if we work at 72p or HD, a Class 6 will be enough, while for higher video resolutions such as 1080p or Full HD we will have to go to a Class 10.

Using the wrong video speed class will not only slow down our work but could harm the internal mechanics of the camera, potentially causing overheating that would stop recording to protect its components.

Therefore, choosing the wrong Class video speed can damage the camera, which is why it is important to coordinate the correct Class video speed with the appropriate device and the image capture speed with which we work.

Extreme conditions

Although the development of solid state represented a great advance in capturing images in extreme conditions compared to rotating magnetic systems such as hard drives, the truth is that in relation to vibration, temperature or humidity, we also found great differences between cards.

Manufacturers like SanDisk have cards specifically developed to work in the harshest conditions. Its Extreme series is designed to withstand extreme temperatures and continuous vibrations. They work anywhere humans can live and work.

But what happens if I unfortunately lose my information? SanDisk, for example, offers its customers data recovery software included free with all imaging products labeled Extreme. In addition, it works with all types of flash memories. Rescue Pro Deluxe is a professional version included in Extreme Pro products and compatible with digital camera converters. To access it, all you have to do is redeem the redeemable coupon with an activation code and obtain a one-year subscription to this interesting service.