Photographers Guide To SD Cards

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Photographers Guide To SD Cards

This blog post may contain affiliate links. I may earn a small commission for any purchases made through these links. Click here for the disclosure statement.

All photos are original to the author unless otherwise noted.

An SD card is the most widely used memory card for cameras, it’s the modern-day version of film where the information for each image is recorded and stored. It’s a small and seemingly insignificant piece of equipment, but without an SD card, the camera is useless. Most of us probably pick the cheapest SD card we can find and never give it a second thought. Any card records pictures, but cheap cards limit how much and how fast you can take pictures even if the camera is capable of more.

Why Should I Care About My Memory Card?

Any SD card records images and does not affect image quality, so why does it matter? The quick answer is speed.

When you first take a picture, it’s stored in the camera’s buffer until it’s saved to the memory card; as the buffer runs out of space, the camera won’t be able to take anymore pictures. So the faster the memory card’s write speed, the quicker the images save to the card and open up space in the buffer. Card speed is the rate the card can read/write data; this is where quality SD cards stand out.

SD Card Capacity

SD or SDSC cards (Secure Digital Standard Capacity) hold between 128MB to 2GB
SDHC cards (Secure Digital High Capacity) holds between 4GB to 32GB
SDXC cards (Secure Digital Extended Capacity) holds between 64GB to 2TB
SDUC cards (Secure Digital Ultra Capacity) holds between 2 TB to 129 TB

SD or SDSC cards(Secure Digital Standard Capacity) hold between 128MB to 2GB
SDHC cards (Secure Digital High Capacity) holds between 4GB to 32GB
SDXC cards (Secure Digital Extended Capacity) holds between 64GB to 2TB
SDUC cards (Secure Digital Ultra Capacity) holds between 2 TB to 129 TB

JPEG: 227

RAW: 58

How many photos can my card hold? Well, it depends on file type, file size, megapixels, and a variety of settings and specifications that make it hard to pin down an exact number. Cameras have a counter that shows how many photos available on a card based on your exact settings, so knowing the following calculation isn’t necessary. But if you’re curious, you can calculate an estimate by looking at the file size of your unprocessed images on the computer and use this calculation:

GBx1024/file size = # of photos.

1024 is the number of megabytes in a gigabyte. To calculate how many photos your SD card can hold, multiply the number of gigabytes by 1024 and divide by the average files size in megabytes. For example, my camera’s average file size is 35MB, so my calculation for a 64GB card would be 64×1024/35=1872.

The below is an estimation for a Canon 6D Mark II using RAW files (~35MB file size) and JPEG 100% Quality (~9MB file size)

File Type

How Many Photos Can a 2gb SD Card hold?

JPEG: 227

RAW: 58

How many photos can a 32gb SD card hold?

JPEG: 3,640

RAW: 936

How many photos can a 64gb SD Card hold?

JPEG: 7,281

RAW: 1,872

How many photos can a 64gb SD Card hold?

JPEG: 14,563

RAW: 3,744

JPEG

227

3640

7281

14,563

RAW

936

1,872

3,744

SD Card Speed

Write speed is the rate at which the card records images from the camera and read speed is how quickly the card reads the data when transferring to a computer. Not all photographers need a fast card, but for sports and wildlife photographers or anyone who shoots in continuous mode, write speed is important.

Speed Classes

While there are a lot of technical specs in understanding SD card speed, they aren’t important to identify the right card for you. But if you’re curious, here are the speed class specs.

Class 2: min 2MB/s
Class 4: min 4MB/s
Class 6: min 6MB/s
Class 10: min 10MB/s
- UHS-I: min 10MB/s and up to 50MB/s
- UHS-II: min 20MB/s and up to 156MB/s
- UHS-III: min 30MB/s Bus speed up to 312MB/s

UHS stands for ultra high speed and the maximum MB shows the speed the card can hold for a few seconds; it is not a sustained speed. Minimum speed is the sustained speed the card will never go below.

How to Read an SD Card

Card Capacity
Maximum Card Speed
Card Capacity Type
UHS class rating
UHS speed rating
Speed Class
Brand
Another indicator of card speed. This number is isn’t widely used anymore and is redundant information; you can ignore it.

Which SD Card Should I buy

How Many GB Should I Get?

The average photographer needs between 32GB and 64GB to avoid constantly switching out cards without paying extra for unnecessary space. For reference, I shoot wildlife in burst mode and have never used over 64 GB in a day. Even if you don’t plan on uploading your photos to your computer at the end of each day, I would recommend using multiple small capacity cards rather than one large capacity card because if you lose it or it gets corrupted, you could lose everything.

How Fast Should My Card Be?

When shooting in burst mode, you need an SD card that has write speed of at least 100MB/s. Read speed is only used in uploading photos to a computer and is not nearly as important. There are a couple things that could cause some confusion and leave you a poorer performing card than you thought:

The read speed is typically faster than the write speed, so make sure you a looking at the write speed
Some cards use megabits (Mb) instead of megabytes (MB). There are 8 megabits in a megabyte so a card notating speed in megabits may appear faster if you aren’t paying attention, so make sure speed is in megabytes which uses the capital “B”.

Recommended Purchases

Putting it all together, I recommend SDXC cards with 32GB or 64GB of space and write speed of 100MB/s or more (speed class 10 UHS-III) if you shoot in burst mode. If you do not need burst mode, any speed will suffice.