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Sandisk 64GB Extreme Pro SD Card

Memory Card Performance Testing and Purchasing Advice

When I’m not at my day job or behind the camera at Flutter Focus Photography you will typically find me either in the kitchen, on my phone, or in front of my computer. As you will find out with this and future blog posts, I love technology and I embrace it everywhere I can. I guess that’s partly why I got my degree in electrical engineering, that plus the fact that I love math but that’s a story for another day. I not only like to use technology but I also like to really know how or why something is the way it is and I think that plus my engineering background makes it a lot easier for me to understand when something is worth my money or when something is hype created by the marketing department. That leads me to today’s blog post about memory cards and which cards are worth spending your hard earned money on.


A good friend of ours Russell Caron of Russell Caron Wedding Photography wrote a Blog post titled SD/CF Memory Card Ratings and Symbols Demystified. Trying to read and understand what everything means is a bit of daunting task as there are so many different items on the front of the cards but Russ did a great job explaining everything. This got me thinking about what all this information means to us as photographers when we go to our favorite store and purchase our memory cards.

When shooting a wedding or other event speed is very important so it would seem to make sense that buying the fastest memory cards possible would be the best option.  The published read and write speeds for a particular line of memory cards are best on lab tests and are not necessarily indicative of the actual performance you will get in the real world. I’ve purchased memory cards in the past that I thought were very fast cards only to get them home and have them take forever to copy data to and from. Only after reading the fine print did I realize that the maximum read speed which was the published speed on the packaging was very fast but the maximum write speed which was not listed on the packaging was not very fast. It’s very frustrating to spend your hard-earned money on something only to realize that what you bought was not what you thought it was. I’m hopeful that after reading through this you will have a few more tools in your belt that will prevent you from making the same mistakes that I have in the past when you go out to buy your memory cards.


I currently only use SanDisk memory cards in our cameras. SanDisk is a company that has been around for a long time and is a company that I trust with our most important data that we have which is your images. There are other memory card manufacturers out there and some of them even make a great product that will likely never fail you. I’ve used SanDisk products for years and I feel as though SanDisk has two important things behind them though that sets them apart.  First, their products are a great value. SanDisk does not sell the cheapest memory cards nor do they sell the most expensive but I feel that for the money that they charge you get the most bang for your dollar. For me that is important because it gives you a reliable, fast memory card at a price that doesn’t break the bank. Second, the SanDisk Extreme Pro line of SD Cards (and possibly others) come with two years of free recovery software. I’ve personally never had a memory card fail on me but I have had other people reach out to me with memory cards that have failed and I’ve used the recovery software to extract their images that they thought were gone forever. In this industry having a memory card fail and losing all your images is one of the worst things that can happen.

In my last blog post I told you all about the new 5D Mark IV camera bodies that we recently purchased. As I explained the Canon 5D Mark IV has two memory card slots.  This is a common feature in high-end professional cameras.  In the case of the 5D Mark IV it has one Extended Capacity Secure Digital (SD) slot and one Compact Flash (CF) slot.  All of the testing that I’ve done was using the 5D Mark IV and SanDisk 64GB Extreme Pro CF and SD memory cards. For the Extreme Pro SD cards SanDisk currently manufactures two different versions both of which I tested here.  The first is their UHS-I card with a rated maximum read speed of 95 megabytes per second (MB/s) and write speed of 90MB/s. This card has a rated minimum write speed of 30MB/s. The second is their UHS-II card with a rated maximum read speed of 300 MB/s and write speed of 260MB/s. This card also has a rated minimum write speed of 30MB/s. For comparison the CF card has a rated maximum read speed of 160 MB/s and write speed of 150MB/s and does not have a rated minimum write speed.

Something to keep in mind is that I found out after reading the fine print on the specifications for the 5D Mark IV is that it does not contain the technology to take advantage of the UHS-II cards additional speed. I had previously purchased 4 of the UHS-II cards thinking that faster was better. For those wondering what the difference is between the UHS-I and UHS-II SD cards the cards are physically the same size and look almost exactly the same except with you turn the cards over the UHS-II cards have an additional row of contacts on the back of the card.  This allows for much higher read and write speeds as evident by the much higher rating for their read and write speeds.

For connecting the cards to our computer, I purchased a USB 3.0 hub from Lexar a few years ago. When I bought the hub, I purchased two SD card readers and two CF card readers for it. All data was copied over to our ioSafe network attached storage enclosure that I have outfitted with two Western Digital Red drives that I have setup with Raid 1 using Windows File Explorer.  What that means in simple language is that I have a fire and waterproof hard drive enclosure that I have plugged directly into the back of a router that contains two hard drives each of which are mirror images of each other that all of our images are saved to.  

I also did some real-world testing to see how much card speed affected the number of images that I can take with my 5D Mark IV. For this test I pressed the shutter release button for exactly one minute and then I checked to see how many images I had taken. This is a bit of crude test and something that I would never do when shooting in a real situation but I felt it allowed for any gross and obvious differences between the cards to become apparent. Our normal workflow is to have both an SD and CF card loaded into the camera and the camera set to save every image taken to both cards so that you have two cards with exactly the same images on them. In the unlikely event that one of the cards fails the other card will still contain all the images taken. For this test I loaded each card individually into the camera (not our normal workflow) as well as each of the SD cards with the CF card so I could see if there were any speed differences when writing to both card at the same time.


The results from my testing is summarized in the chart below and I have to say that the results are not what I was expecting. I bought four UHS-II SD cards at a cost of over $400 because I thought that having the fastest possible cards would really help to speed up our workflow. What I found is that the technology in the 5D Mark IV and my computer setup are really the limiting factors for how fast I can take and download images. I also didn’t realize that when using both an SD and CF card that I was limiting the speed of the 5D Mark IV to the slower speed of the UHS-I SD card.  This is something that I should have realized but it didn’t click until I did these tests. I was also surprised to learn that no matter which card I was using it took roughly the same amount of time to download my images to the ioSafe. For a full 64GB memory card the difference between the slowest and fastest cards is only about one and half minutes.  

Device Type

Software 1*

Software 2**

Transfer Speed to ioSafe

Stand Alone Camera Speed (Images per Minute)

Camera Speed with CF Card (Images per Minute)


Read Speed

Write Speed

Read Speed

Write Speed

Compact Flash



























In order to be thorough, I also did some additional testing to determine how fast each of the 5 different hard drives that I have in my computer actually are as well testing with each of our Dell laptops that we purchased last year. Speeds ranged from approximately 50MB/s for my slowest drive to almost nearly 500 MB/s for the solid-state hard drives that we have in each of our laptops. For the Western Digital red drives in my ioSafe testing resulted in speeds of 117MB/s. I was not surprised to see that the test results for the Western Digital red drives in my ioSafe were on the slower side. These drives are designed and built to be super reliable so that they can be used in a small business environment where you are constantly accessing your data. These drives are also installed in my ioSafe which is a sealed unit with little airflow for keeping the drives cool. In order to get reliability in this type of environment speed had to suffer.

Transferring images to our laptops also resulted in some additional interesting results. When using the built in SD card slot speeds were limited to approximately 30MB/s. Only when plugging in one of the external Lexar card readers was I able to achieve maximum transfer speeds from each memory card.  Also, only when transferring images to the solid-state hard drives in our laptops and on our desktop was I finally able to take full advantage of the additional speed of the UHS-II SD cads. Going into all this testing this is not something that I had anticipated. I knew that the drives in my ioSafe would be slower but I never expected the UHS-II cards speed to only be taken advantage of by the  super-fast solid-state hard drives. Based on my testing for downloading a completely full 64GB card the UHS-II card would save just over 3 minutes when compared with the CF card and just over 7 minutes when compared with the UHS-I memory card.

Conclusions and Suggestions

After all of my testing I have come to some conclusions and suggestions to help you with your next memory card purchase which I have summarized below.

Check your camera and computer hard drive speeds to see just how fast they are. If you have a slower camera and a computer with slower hard drives there is no need to spend additional money on faster memory cards.
If you are using a built-in memory card reader test its speed. If it is slow and your computer supports USB 3.0 or another super-fast connection method consider buying a separate memory card reader. The Lexar SD readers that I use with the Lexar hub are less than $25 and I was able to get speeds that were nearly three times faster even with the slower UHS-1 SD cards.
Read the fine print on your memory cards to see exactly what the rated read and write speeds are before you purchase. As my testing showed I was never able to achieve the maximum rated speeds for the SanDisk memory cards. Based on what I’ve seen previously with other memory cards and what I’ve read from testing results done by others this seems to a common theme with most memory card manufacturers. Having a slower memory card is not a bad thing but will likely stop you from getting full speed out of your camera and it will also take you considerably longer to download your images to your computer.
Checking prices on SD cards on 01/21/2019 from B&H found that for a 32GB card the prices ranged from $8.99 for the slowest SanDisk card to $14.75 for their fastest rated UHS-1 card. In my opinion this is a no brainer. Spend the extra money and get the faster UHS-I card. Unless your camera has the technology to take advantage of the faster UHS-II memory cards and you’re constantly pressing down on the shutter button and shooting several pictures at once be it sports or other events or you have a computer with a very fast solid-state hard drive than it is not worth spending four times as much ($59.95) for the UHS-II memory cards.
Purchase your memory cards from reliable sources. There recently has been a huge influx of fake memory cards. I’ve heard several stories of fellow photographers that have purchased what appeared to be real memory cards from places like Amazon only to have the cards arrive and find out that they are fakes. A quick google search finds lots of articles on how to tell if your memory cards are fakes. Purchasing your memory cards from trusted places like B&H or if you purchase them on Amazon ensure that they are shipped and sold by Amazon and not from third party retailers helps ensure that you are getting the real deal and not a fake. If your looking somewhere local to make your purchase Hunts is always a great option.
If you have a high-end camera with dual memory card slots always take full advantage of this feature by having your camera setup to write every image you take to both cards. If your camera only has one memory card slot either change out your memory card or download your pictures to your computer often if you are taking pictures of anything of value. For me that means any time I’m taking pictures of anything that cannot be easily redone like a wedding, corporate event or party.
Always keep a spare set of memory cards just in case disaster strikes. Even if you purchase the most reliable cards disaster is bound to strike at some point.

Contact me with any technical questions you have or would like to see in future blogs!

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