SD Card Ratings Guide: How To Select the Best SD Card for You

Just as a traditional camera needs film, a digital camera needs memory. At the dawn of digital photography memory chips came in all shapes and sizes and several camera manufacturers even made their own proprietary and expensive memory devices. However, today things have changed, and the Secure Digital Card (SD Card) has become the industry standard similar to the way 35mm film became the standard in traditional photography. In this SD card ratings guide you will learn how to best select an SD card for your application.

SD Cards are used in everything from smartphones to tablets even MP3 players. These versatile, inexpensive forms of memory can be found everywhere. Although they look the same there are some differences you need to be aware of before purchasing an SD card for your camera.

In today’s lesson, we will go over the three variables that you need to be aware of before selecting an SD card. These three variables are speed class, size, and capacity.


SD cards come in six different speed classes. The speed of an SD card determines how quickly it can take data from the camera and write it onto the memory card. Imagine if you will a tiny elf residing in the SD card. His job is to take the image he sees then, as quickly as possible, draw that image onto a canvas. The faster this little elf can draw, the faster you can send him new images. That might seem silly, but essentially that is what is happening inside the SD card. Images come in; the SD card then writes them digitally into its memory.

If you are shooting in RAW mode (the mode that requires the most memory per shot) and you want to shoot a rapid series of shots, you are going to need a faster card. If you are a casual photographer and do not shoot video, a lower-speed card will suit you just fine even if you are using RAW or other high-resolution settings.

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These six classes are divided into two groups the first group is called the C speed class. In this group, there are four different classifications 10, 6, 4, and 2. The slowest of these classes is two while ten is the highest. Unless you are shooting “full resolution HD video,” most amateur photographers will do just fine with a class 4 or 6-speed class.

The second group of SD cards is called Ultra High Speed (UHS). These cards are very fast and significantly more expensive. These are used mainly by broadcast professionals and photographers who shoot 4K video. They classified into 1-class and 3-class, one being the slower and three being the faster.

The ratings of these cards are printed on the label of the SD card as well as on the packaging. The C-Class rating looks like a number inside a C, while the UHS rating is a number inside a U.



There are three sizes of SD cards, standard, mini and micro. While all three types are relatively small, standard SD cards are the largest of the three. They measure 32x24x2.1 mm and weigh two grams. Mini SD cards are the second largest measuring 21.5x20x1.4 mm and weigh 0.8 grams. The mico SD cards are the smallest of the three and measure a mere 15x11x1 mm and weigh only 0.25 grams.

When it comes to choosing the proper size of SD card, you need to check your device. Every camera uses a different size SD card. On a side note, many micro SD cards come with a standard SD card adapter. This is convenient if you want to utilize the small size of a micro SD card, but your camera requires a Standard SD card.

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Simply defined, capacity is the amount of available storage on an SD card. SD cards are much like USB flash drives in that they are a solid state (meaning no internal moving parts) form of memory. Also just like USB drives their prices can vary widely depending on their capacity.

There are three classes of SD card capacity. Let’s start from the lowest and work our way up.

The lowest capacity class is SD Standard Class or SDSC for short. These cards generally have 1MB to 2GB of storage. Regarding how many photos you can hold, a 2GB SD card can hold about 950 images shot at 6 Mega Pixels. All cameras that use SD cards cameras can use SDSC cards. You will hardly see these in existence today, as user storage needs continue to grow. What can you do with 2GB these days?


The next class of SD card is the SD High Capacity class. Most modern day cameras can use this type of card. The cards are rated from 2GB to 32GB of storage. Regarding photos, if we are shooting in JPEG format at six megapixels, we can store over 15,000 images on one card.


Taking the top spot in the capacity rating is the SD Extended Capacity (SDXC) Card. These are used mainly by professionals and if you want to use one, check your camera’s owner’s manual to see if your camera can use an SDXC card. Some of these cards can hold up to 2TB of data! Yes terabytes. To use our above example of shooting with a six-megapixel camera, a 2TB SD card could hold a lifetime of photos with over 300,000 images. However, that it will hold about 20 hours of 4K video. This is why these cards are used by professionals shooting 4k.

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One caveat though, I would NEVER recommend that anyone use such a large capacity card for photography – or rather I wouldn’t use it until full. Reason being that sometimes memory cards can spontaneously get corrupted resulting in data loss. Can you imagine losing 2TB worth of pictures?! It would probably feel like the end of the world. Instead, I suggest using multiple lower capacity cards in rotation and transferring your images to your computer after every use. This will minimize your losses in the event of a catastrophe.

Personally I use 16, 32 or 64 GB cards in rotation – all affordable capacities that provide substantial storage for any photography enthusiast and even some professionals.

If videography is your thing then I would suggest larger capacity cards depending on your needs.



When it comes to selecting an SD card you need to consider your shooting style. Are you just getting started and you take your time to frame each shot? Then a slower, lower capacity SD card will suit you just fine. Do you have a young child and want to shoot them in HD video? Perhaps a faster card with higher capacity will work for you. Are you an aspiring freelance journalist with the latest 4k video camera? In that case, you will need a high speed, high capacity SD card.


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