Recently, I had someone write to me and ask me some questions about the best way to use memory cards in Canon cameras. I started to write back to him and then realized that this is good information to share with all of you as well. Hence this blog post.
My goal here is to help you shoot more efficiently in your camera. Believe it or not, the way that you shoot your images to your memory cards does have a big effect on the performance of your camera. Answering questions like "Should I use both memory card slots?" and "Should I shoot RAW to one card and JPEG to the other card?"
Since I am a Canon user and very familiar with their line of cameras, this blog will mostly be focused on their cameras, but rest assured, this information will still be useful for all you other camera owners. Hopefully it will inspire you to learn more about your camera's memory card slot(s) and help you get the most out of your camera.
The different memory card slots in cameras
As camera technology has evolved, so have the memory cards which go in those cameras. Actually, this whole process is a bit of a chicken and egg situation. The camera companies are hesitant to adopt newer memory card formats until the cards are readily available, and the memory card companies are hesitant to ship cards if there are no cameras which use the technology. So, each time a new card format is announced, it takes a while to determine which technology will stick and which will not.
If you look back, you will see that there were many types of memory cards that came out and didn't last very long. Formats like MiniSD, MMC, xD, Memory Stick M2 came and went pretty quickly. The most common memory cards used today are Compact Flash (CF), Secure Digital (SD), with the common new comers being XQD and CFast. But even with these form factors, there have been many iterations of each of them and the camera companies have not always been up-to-date with the latest technology when releasing their cameras. It is for this reason that you need to be aware of your camera and what its data moving capabilities are.
Redundant shooting to two cards
Having spent 12 years in the memory card business, I can tell you that there is no memory card that will last forever. Since I value every photo I take, I almost always recommend shooting to two cards. Today I am using
Pro Grade Digital memory cards because I think they are the best on the market, but even using the best, I still want to protect myself from potential card corruption.
Shooting RAW to both slots or RAW to one and JPEG to the other?
Before heading to the 2012 Summer Olympics in London, I had a plan to shoot full sized RAW images to one card of my Canon 1D X and medium sized JPEGs to the other card slot. I figured that, with this method, I would be able to write faster to both card slots (since the second card would be writing a smaller file than the first card) and I would be able to store a ton of images on the second CF card. Well...after testing this, I found that the camera was taking twice as long to clear it's buffer. This surprised me and lead me to some more testing and phone calls to the technical people at Canon. As it turns out, when writing both a RAW file and JPEG file (to one card or two) the camera has to process both formats, which takes more time. It is for this reason that I never shoot in RAW+JPEG mode. I almost always shoot RAW to both card slots. Heck, if I need JPEGs, I can convert my RAW files to JPEG on my computer in seconds.
Cameras with two different types of card slots
The Canon 1D X camera had two Compact Flash slots, which meant that both slots allowed me to write at 1066x speed. But many cameras have come out with different types of slots in the same camera body. The
Canon 1D X MarkII has a CFast slot and a CF slot, which means that one slot can write at a blazing speed of 3500x and the other can only write at 1066x. When I shoot to both cards (which I mostly do) I am now limited to 1066x for the maximum write speeds.
The same is true when I shoot to my Canon 5D cameras, which combine a CF card slot and a slower SD card slot. More on that in a minute.
The cameras memory buffer matters too
As I just mentioned, when writing to both the CF card and CFast card on my
Canon 1D X MKII, it does slow the write speed, but luckily the memory buffer in the camera is large enough that this is rarely an issue. This is less true on the
Canon 5D MKIV which has a smaller internal buffer. The smaller the buffer size, the less the camera can hold internally. For cameras with smaller buffers, it is even more critical to write to the memory cards fast. You need some free space in the buffer before you can take more photos.
Why does Canon ship with different card slot types in one camera?
Canon is a very conservative company which has been hesitant to release a new camera with an unproven card technology. For this reason, they have created cameras with one newer card technology slot and one older slot. They feel that this helps photographers who have a large investment in the older memory cards, and also helps them hedge their bets with the new formats. I understand that thought process, but it does hinder the new camera when it comes to the optimum writing speed.
Compact Flash (CF) slots
CF cards have reached the end of their development lifecycle and what we have today is the best that the cards will ever do. Yes, that 1066x speed that you see on most CF cards is the best they will ever achieve. And for the last 5 years, almost all cameras that have come out with CF card slots have been able to take full advantage of this speed. Why? Because the cameras were designed with memory card slots that took advantage of the final spec (called UDMA 7). Because the cameras and cards spoke the same "language", the performance was optimal.
Secure Digital (SD) slots
SD cards have been around for a long time, but have changed a lot in all those years. They have increased wildly in their capacities and speeds, but because of all those changes, not all cameras can use all SD cards at their full potential. When the Canon 5D Mark II came out, the SD card slot did not support the then current SD speeds and seriously hampered the performance of writing to the SD memory card in that camera. Then, with the release of the Canon 5D Mark III, I was looking forward to a faster SD card slot, and Canon totally let me down. Their engineers in Japan who designed the camera failed to include the current technology (called UHS) once again. Arghh!!! Then, after waiting another couple of years, Canon announced the
Canon 5D Mark IV and I thought "for sure Canon has finally put the latest in SD card slot technology into their camera" and once again I was let down. Yes, they did put a SD UHS-1 slot in the camera, but UHS-2 technology has been out for more than 7 years.
What does this mean to you and I? It means that, when writing to both memory card slots of the
Canon 5D Mark IV, with one being a lot slower than the other, the camera takes a lot longer to write the data and clear the buffer. So...we have to wait longer to shoot more images. Today, if I am using the
Canon 5D Mark IV for shooting sports, I have to shoot only to the CF card. Otherwise I have to deal with the frustration of the "Please Wait" message on the camera as I watch action unfold in front of me.
Newer and faster memory cards
The fastest memory cards on the market today are the CFast and XQD cards with speeds ranging in the 3500x range. But, as I have mentioned in previous blog posts, it looks like we are about to see the new CFexpress card format very soon. These cards have the ability to write at much faster speeds than CFast and XQD. But the big question is: Will Canon and other camera companies release a camera with two of these card slots or will they have one CFexpress slot and one older slot? Only time will tell.
I hope this helps you understand the subject a little more, and helps you shoot more efficiently in the future.
Related blog post:
Why you should not delete images in your camera
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