Long gone are the days when firing the shutter was the culmination of careful planning and skillful crafting.
Some people use this argument to bash the value of digital photography (and digital photographers), with spray and pray being common practice, particularly among beginners.
It is not difficult to come back from a day-long family excursion with a couple of hundred photos.
But back in the heydays, photography was a far more expensive hobby/job: not only did you have to pay for the gear, same as today, but also for the film, its development and photographic prints. And you only had 12, 24, or 36 exposures per roll of film.
No wonder photographers were very, very, careful about pressing that shutter button.
Today, we have no film rolls but virtually unlimited digital storage capabilities thanks to memory cards.
Different types of memory card
When I got my first digital camera, it had a few megabytes (MB) of internal storage and I could use Compact Flash (CF) cards. I remembered I had one with 32 MB of storage.
This was a game-changer: while laughable by modern standards, at the time, with those low-resolution sensors and shooting in JPEG, it offered plenty of storage.
And with every passing year, memory cards grew in storage while shrinking in physical size.
All Memory cards are non-volatile, read/write solid-state memories to be used in electronic devices such as digital cameras, smartphones, etc.
They are small, lightweight, durable, affordable, and easy to use.
Compact Flash (CF) Cards
CF were one of the first types of memory cards. The first CF card was made by Sandisk back in 1994 and became the standard for digital cameras.
Early models could only offer up to a few MB of storage, but during the years they grew massively, arriving to offer 512GB of storage.
CF cards have now been replaced by the Secure Digital (SD) standard in the majority of the cameras available in the market. However, both Canon and Nikon are still using CF cards for their flagship cameras.
Secure Digital (SD) Cards
Secure Digital, officially abbreviated as SD, is a proprietary non-volatile memory card format developed by the SD Association (SDA) for use in portable devices.
The standard was presented in 1999 and developed by SanDisk, Panasonic, and Toshiba.
SD cards are much smaller than CF, and thanks to progress in miniaturizing electronic circuits, they are able today to offer up to 128 TeraByte (TB).
SD cards come in different flavors: SD, SDHC, SDXC, and SDUC. They all share the same physical size, and your camera may be able to use all those variants.
SD cards are today’s standard in photography.
MicroSD are memory cards that are even smaller than the SD ones, and are mostly used in smartphones, tablets, and raspberry pi computers such as the ZWO ASIAIR and Stellarmate.
Like the SD cards, they too come in different flavors, such as the MicroSDHC and MicroSDXC, the latter available with 1TB storage.
Those cards differ by the type of file system they use: FAT32 is the oldest type of file system that cannot manage more than 32GB. Larger cards are formatted in the exFAT32 file system and to use them, your camera must be able to use this type of file system.
Card Speed: Should I Care About It?
When you use a memory card, there is more than the mere storage capacity to look for: their reading/writing speed.
If reading speed is not really important (you can always go making a cup of coffee while waiting for your images to be downloaded), writing speed is rather important.
If you are into action photography, sports photography, and wildlife photography, you probably need to take images in rapid sequences to capture the unfolding of a moment. All those images go into a buffer, a temporary storage where data are conserved while waiting to be written on your SD card.
But if the writing process takes too long, the buffer will become full and no new images will be recorded. The larger your image files are, the faster your SD card should be in saving them.
And this is crucial if you shoot videos with your camera.
A class 10 SD card is probably the slowest usable type of card with today’s photo and video cameras.
File Type Makes A Storage Difference
The amount of data you can store on your SD camera is difficult to estimate, as this depends on the image format, image resolution, image compression, and video quality.
JPEG is a compressed format. Your camera will use compression algorithms to compress your image before writing it on the camera. Your RAW image is not saved and, therefore, is lost forever.
You can choose the quality (compression level) of the JPEG images: usually you can set it to small, fine, and ultra-fine: the higher the JPEG quality, the more space the images take up on your memory card.
Note that when you save images in JPEG format, cosmetic effects can be applied by the camera to the image before it is saved, like color filters, noise reduction, and sharpening.
Raw images are, loosely speaking, what your sensor sees, without much alteration, if anything at all. Their size depends on things like sensor resolution (megapixels), bit depth, and compression.
RAW images are always larger than the best quality JPEG image, and if you often shoot in this format, you should use cards with large storage space.
Each RAW image from my 20MP Sony RX10 always takes up about 21MB on my card, while I can have JPEG images as small as 2MB or less.
RAW files are not readily used, and you need to post-process them with editing software such as Lightroom, Photoshop, Gimp, and Darktable, to name a few.
In-camera cosmetic settings are not applied to the RAW image: noise reduction, sharpening, picture styles, and even white balance only affects the embedded JPEG preview, the one you see on your camera LCD screen.
All cameras allow you to save images both in RAW and JPEG formats. This is the most storage-consuming option when it comes to saving still images on your memory card.
It is useful if you are on outings and want to share your photos quickly or when you know you will only want to edit the best images from RAW.
Nowadays, all digital cameras can take videos, and this is by far the fastest way to eat through multiple SD cards.
Video resolution and video quality strongly affect how much you can record on the SD card: a 4K video will take up far more space than one in HD format.
Mind that because of legislation, at least in Europe, photo cameras cannot shoot videos longer than 30 minutes, so they will cut the video off after 29 minutes and 59 seconds.
Videos are saved “live” on your cards (which is why you need a fast one), and if the video file exceeds the limits of the card file system, a new file will be created. So mind that while you have shot a single clip, you could end up having multiple files on the card.
To further save space, some cameras allow you to change the resolution of your JPEG images. My Sony RX10 allows me to save JPEG at 20MP, 10MP, and 5MP.
How Many Pictures Can I Store On My Memory Card?
It is quite difficult to make an estimate on how many images you can store on your card or per GB.
As we saw before, this depends on the type of images you want to save, their resolution, and their quality. And the same is true for video.
When you buy your card, on the package you should find some estimates made by the manufacturer for the different types of data you could store (MP3, MPEGs, JPEGs, etc.)
Even for the RAW file, there is not a 1:1 correspondence between the image size and the sensor’s MP or resolution.The size of a RAW image file also depends on the RAW bit-depth, 12-bit or 14-bit, and if the camera compresses the data or not.
Did You Know?
Because JPEG images are compressed images, their final size depends on the type of image you have: images with lots of Bright/Dark tones and large homogenous parts (think of the sky or the sea) can be compressed more and take up less space on your card.
The same is true with videos, depending on the bitrate you choose.
RAW files are slightly affected by the type of scene too, but in a far smaller amount than JPEG images and video files.
All in all, the best estimate comes from your camera itself: on the LCD, you always find the reported number of remaining images (or video time) you can store on the card with the current settings.
What To Look For In Memory Cards For Astrophotography
Astrophotography is highly demanding in terms of storage: aside from photographing in RAW only, you will be taking photos of the same targets per several hours at a time.
Plus, you have to think about calibration files (also in RAW): Darks, Bias, Flats, and Dark Flats images take up a fair amount of space on your camera.
And if you are doing lunar and planetary astrophotography, you may find yourself wanting to shoot high-quality videos that, although not long, will still eat up a fair amount of space in your memory card.
One bit of good news is that you do not need a crazy-fast memory card, particularly if you do not do videos: deep space astrophotography is the realm of long exposures, so your camera has plenary of time for writing your previous image on the card, never filling up the camera buffer.
If anything, pack a spare card in the bag for, you know… just in case.
Memory cards are used in a wide range of electronic devices, from camera phones to digital cameras, from tablets to raspberry computers.
While it is difficult to predict how many images you could save per GB of storage space with your setup, it will be quite difficult for you to fill up one of the latest cards, as those offering 128GB or more of storage space are common and quite affordable.
And if you are a videographer, remember to get a card with a writing speed fast enough for the type of videos you make (full HD, 4K, or even 8K).