I won’t be the first one to tell you that fast cameras need fast memory cards. However, even the fastest cards differ in their read/write speeds between the theoretical and the actual achieved speeds. Read/write times not only depend on the tech specs of your card, but also your camera and transfer devices.
In the field, card read/write speed affects not only how fast the camera’s buffer can clear, but also how fast you can copy images to your computer. When transferring your images to a computer, the following factors are important to consider:
- Card Speed
- Reader Speed
- Reader Interface (eg. USB/Firewire)
D810 Performance with CF Cards
I compared download speeds for 27 images (14-bit, lossless compressed) from the Nikon D810 using two different cards:
- SanDisk Extreme Pro (90MB/s) UDMA 7 CF 16GB card
- SanDisk Extreme Pro (160MB/s) UDMA 7 CF 32GB card
I tested each card using the Hoodman Raw Steel reader via USB 3.0 and USB 2.0 interfaces. I downloaded my images to my computer using Photo Mechanic 5 and my typical settings. These settings included file renaming and adding IPTC data to each image as it was copied.
I tested the buffer performance by setting the D810 to capture 14-bit lossless compressed full-size raw images (NEF format) in continuous high-speed release mode (5fps). I determined the number of images I could capture before the buffer was full, and I timed how long it took for the buffer to clear. With these settings, the buffer count shows 19 frames.
Comparing cards, it’s clear that the newest SanDisk Extreme Pro card, which is rated to 160MB/s, is faster than the previous version rated at 90MB/s. The new card was about 52% faster than its predecessor. For pros working in the field, this speed difference is noticeable. You could transfer 30GB of images in just over four minutes with the 160MB/s card, while the 90MB/s card would take almost seven minutes.
Note that neither card delivered download speeds at their theoretical maximum transfer rate. Transfer rate depends not only on the card, but your reader and transfer utility. The process of adding IPTC metadata and renaming my image files (something I always do) slows down the transfer speed. The USB 3 interface was 2.4x faster for the 90MB/s card, and over 3x faster using the new 160MB/s card. With USB 2, the difference in performance between the two cards was much less noticeable, with the 160MB/s card being about 15% faster.
The other factor in image transfer time is the interface speed and having a device that can support faster interfaces. Because the Hoodman Raw Steel reader supports USB 3, I was able to test it with both USB 3 and USB 2 connections. When I used the USB 2 both cards transferred data more slowly.
Buffer Performance in the Nikon D810
The other area where you might expect to see speed gains when using fast memory cards is in the camera buffer. The faster a camera can write to a card, the faster the buffer should clear. A side-product of fast write speeds is that the actual buffer size can theoretically be larger than what is indicated by the camera, because the camera can clear data from the buffer during continuous shooting, thereby freeing up buffer space.
The Nikon D810 can shoot 5fps. With the 90MB/s CF card, I was able to capture 23 continuous frames before the buffer filled. With the 160MB/s card installed, I was able to get 26 frames before the buffer filled. The camera cleared the buffer about one second faster using the 160MB/s card.
Whether you are a high-volume shooter or capture images with a high-resolution camera, the benefits of a fast card and card reader are apparent. In the field, having a fast card means you will be able to clear your buffer faster, which can mean being able to capture more frequent bursts of images.
The other advantage of a fast card is in data read speeds when transferring your images to a computer. You can save a significant amount of time if you have a fast card and a USB 3.0 compatible card reader. However, if you use these fast cards and readers with a USB 2.0 interface, you won’t get anywhere near the maximum transfer speeds. For the best performance, use a USB 3.0 reader with a USB 3.0-enabled PC or Mac.
The Hoodman Raw Steel USB 3.0 UDMA reader is available from Hoodman USA. You’ll need a computer equipped with a USB 3 port to take advantage of it’s full potential, but you can still use it via USB 2.0 ports in a pinch.