The Need for Speed: Newer DSLRs and UDMA

With many of the newer Digital SLRs now including Ultra Direct Memory Access (UDMA), we decided to take a look and see how much improvement there really is in terms of performance. UDMA is a technology that provides extremely fast read/write access to a camera’s memory card, especially when an UDMA-equipped DSLR uses an UDMA‑compliant memory card. So, if you are a photographer who is looking to potentially speed up your workflow, this information is sure to be worth your time.

When we last published a review of CompactFlash (CF) cards in May 2008, “Not All Memory is Created Equal,” there were only three UDMA-equipped DSLRs on the market: the Nikon D3 and D300, and Canon’s 1Ds Mark III. Also, at that time only four manufacturers—Delkin, Hoodman, Lexar and SanDisk—were offering UDMA-capable CF Cards. The following tables detail the test results from that article and show the performance differences between the various memory cards.

The published results were a real eye-opener to those photographers who gave little thought to memory cards, and still others who were more inclined to buy strictly on price. When you consider the number of digital images a photographer will take at an event, ranging from hundreds to several thousand, even a small time savings multiplied many times is something that is sure to benefit a photographer’s overall workflow. As many have said, reducing time in front of a monitor means more time shooting, which in turn means more opportunity to gain additional revenue.

Cards and Designated Speeds
Memory cards typically indicate their speed by designations such as 150X, 300X, and in some instances 30MB/s or 45MB/s (MB per second). To convert the MB/s to a speed rating such as 300X, you should know that 1X equals 150K/sec. Now simply divide the maximum transfer rate shown in MB/s by 150K and you will find that the newest SanDisk Extreme IV rated at 45MB/s is the equivalent of 300X. The SanDisk Extreme III rated at 30MB/s is the equivalent of 200X. While many think the speed rating of 200X or 300X is something that they can easily use to compare one card’s performance to another, when you review the timings shown in Table A, you quickly realize this is not the case.

Speed designations refer to the minimum sustainable rate that data can be transferred to/from the memory card. Each card’s rating and consequently speed designation is actually based on that manufacturer’s own internal testing. Because the criteria used for testing differs with each manufacturer, comparing one manufacturer’s CF card rated at 300X to another’s also rated at 300X is like comparing apples to oranges. In some instances, a CF Card that bears a lower speed designation can actually perform better than one with a higher designation.

Transfer Rates and Compact Flash Card Testing
The original methodology for transferring information in/out of a CompactFlash card was called Programmed Input/Output, or PIO. It is grouped into seven modes, each relating to a specific transfer rate. Table B shows the PIO modes and their associated transfer rates. UMDA is a newer technology and offers six modes shown in Table C. When you look at the tables it is clear to see that UDMA is a technology that provides a much faster means of transferring information compared to PIO.

With UDMA becoming more commonplace in DSLRs and CF Cards, we decided to run a test to see just how much improvement one would see in performance when using this new technology. All CF cards included in the test were UDMA-compliant. Even though the SanDisk Extreme III and RiData CF cards were not labeled as being UDMA-compliant, both the SanDisk and RiData websites indicate they are UDMA-compatible. Kingston representatives stated their CF Cards were UDMA-compliant, but this is not indicated in product literature or on their website.

For our test we wanted to mimic real-world use. To do this we placed each of the CF cards listed below in a Canon EOS 50D and then in a Nikon D3, set each camera to record RAW plus large JPEGs, and the motor of each to continuous high-speed operation. We then set the lens to manual focus, left the lens cap on, set the camera to Manual and used a shutter speed of at least 1/1000 and a small aperture. We fired off 10 images and used a stopwatch to time the results.

The Canon EOS 50D was simple to time since the red LED illuminated constantly until writing to the CF card completed, then turned off. The Nikon D3 was more difficult to time as the LED flashed on/off until it completed writing. In the end we opted to shoot 8 to 10 images with the D3 and see how long it would take for the camera to write that amount of information to each card. We also took advantage of the image counter display on the rear-LCD display of the D3 that changed incrementally as each image was written to the CF card. We ran more than six passes with each card in the camera to ensure accuracy, averaged the timings and placed the results in Table D below.

Table D compares the speed of each CF card in a given camera and does not compare one camera to another. The rankings shown were developed using a consistent number of images with each card in a given camera. Bear in mind, even if the number of images were different between cameras, it does not matter as long as the same number of images were used when testing each card in that camera.

In terms of sheer speed, the Hoodman 300X UDMA CF card was the clear winner. It was better than the SanDisk Extreme IV UDMA and Lexar 300X UDMA cards in terms of speed by 4% to 39%, depending on the camera used. We were fortunate to be able to test the new RiData 300X Supreme Series UDMA card and found it to be nearly as fast as the Lexar 300X when used in the Canon EOS, but the surprise was that it was slightly faster than the Lexar when used in the Nikon D3.

For the photographer who has a need for speed and wants to maximize workflow, the Hoodman 300X, closely followed by the Sandisk Extreme IV, Lexar 300X, and new RiData 300X Supreme Series UDMA cards are the ones to look at.

Table A: Camera Timings in Seconds
The original timings, as published in Rangefinder, May 2008, showing the amount of time each camera needed to write a set number of images to each CompactFlash Card.

EOS 40D    EOS 1D      EOS 1Ds     Nikon    Nikon
Mark III       Mark III*     D200    D300*

Delkin 305X*                  18.5             26                17.5             41       11.5
Hoodman RAW 280x*     19               27                  20              48       13.5
Kingston 266x                  17               24                 16.5            41       10.5
Lexar 300x*                     17               24                 12.5            40          7
SanDisk Ultra II               25               40                   29             59          22
SanDisk Extreme III        19               26                 17.5            40        10.7
SanDisk Extreme IV**   14.5             20                 11.5            36          4.2
SanDisk Ducati*             14.5             20                   11             36          3.9
*UDMA-compliant
**The SanDisk Extreme IV had a speed designation of 40MB/s at the time, the
equivalent of 266X.

Table B: PIO
PIO (Programmed Input/Output) modes and their associated transfer rates. PIO is the oldest method for transferring information to/from a device such as a CF Card.

Programmed Input/    MB/s
Output (PIO)
Mode 6                        25
Mode 5                        20
Mode 4                      16.7
Mode 3                      11.1
Mode 2                       8.3
Mode 1                       5.2
Mode 0                       3.3

Table C: UDMA
UDMA (Ultra Direct Memory Access) modes and their associated transfer rates. UDMA is the newest technology used to move information to/from a device such as a CF Card.

Ultra Direct Memory      MB/s
Access (UDMA)

Mode 6                           133.3
Mode 5                           100
Mode 4                           66.7
Mode 3                           44.4
Mode 2                           33.3
Mode 1                           25

Table D: CompactFlash Card Timings

                                                  Canon 50D           % of additional           Nikon D3           % of additional           Avg % based
CF CARD                                    Time in                 time needed               Time in               time needed to           on Canon &
seconds           to write compared           seconds            write compared             Nikon times
to Hoodman                                              to Hoodman            compared to Hoodman

Hoodman 300X UDMA                   3.75                         0%                          11.2                            0%                             0%
SanDisk Extreme IV UDMA
(45MB or 300X equiv.)                     4.2                          12%                        11.7                             4%                            8%
Lexar 300X UDMA                           5.2                          39%                        12.4                           11%                          25%
RiData 300X Supreme
Series UDMA                                5.4                           44%                        12.2                           9%                           26%
SanDisk Extreme III
(30 MB or 200X equiv.)                    5.7                           52%                         14.4                          29%                         40%
RiData 266X                                     7.8                          108%                           19                           70%                         89%
Kingston 266X                                  9.2                          145%                           23                         105%                       125%
DELKIN Devices
UDMA 305X                                 10                           167%                         26.1                        133%                      150%
Kingston 133X                                11.55                         208%                          33                          195%                      201%

Peter Kotsinadelis is a writer/photographer living in Pleasanton, CA. He may be reached at [email protected]