Pentax FluCard O-FC1 Review


Under the hood, the Pentax FluCard is a fully standards-compliant 16Gb SDHC memory card.  14.9 gigabytes are available to the user for storage. On this page, we will take a look at the card's in-camera write speed, and its performance when used for wireless file transfers and tethering.

When you first power on your camera or insert the FluCard into your camera, PC, or other device, it will take approximately 30 seconds for the card to initialize its wireless network.  During this time, the camera will emit a series of beeps.  Once the beeps stop, the card is ready. For the first few seconds of the initialization process, the card cannot be read from or written to. If your camera automatically goes to sleep, the FluCard will need to be reinitialized after the camera is turned on again by using the controls on the camera.  Fortunately, while the FluCard has an active connection, the camera's auto-off timer is disabled, so you do not need to adjust the auto-off setting yourself.

Write Speed Test

The FluCard is rated a class 10 SDHC card, which means it must sustain a minimum write speed of 10MB/s.  This places it to the mid to lower end of the speed spectrum, as even inexpensive cards offer high UHS-I transfer rates above 30MB/s these days.

In order to test the write speed in practice, we shot a series of continuous bursts with the Pentax K-3 using the FluCard, a Sandisk Extreme Pro card, and a Sandisk Extreme card.  The Extreme Pro card has an advertised maximum write speed of 90MB/s, while the Extreme card has an advertised maximum of 45 MB/s.

For each test, the shutter button was kept depressed until the camera's buffer was filled; once the shutter would no longer fire, we measured the time it took the camera to finish writing the contents of the buffer to the card.  We also checked how many total frames were captured.  The K-3 was running firmware version 1.03.

Extreme Pro
JPEG Fine 66 66 66
RAW 24 24 24
RAW+ 24 24 24
Number of frames at max. FPS

Extreme Pro
JPEG Fine 18s 35s 44s
RAW 19s 33s 45s
RAW+ 26s 44s 62s
Time to clear full buffer
(measured from end of burst)

After tabulating these results, we used desktop software to test the actual write speed of the card, which we found to be approximately 18MB/s.  We also tested the average read speed while transferring K-3 photos from the card, which turned out to be just over 10MB/s. For reference, Pentax K-3 24-megapixel JPEG files are typically in the 15-20MB range.

An interesting observation here is that while the faster Sandisk cards greatly shorten the amount of time you have to wait for the buffer to clear, they don't offer an increase in the maximum number of frames that can be captured during each burst.  This was not the case when we tested the K-3 with the original firmware, which leads us to suspect that Pentax engineers changed/improved the way files are stored in burst mode.  With firmware version 1.00, the Extreme Pro card only allowed a maximum of 52 frames at maximum FPS.  We can therefore conclude that the firmware update makes the K-3 more friendly to slower cards, even though it does not improve the wait time associated with using such cards.

The bottom line in terms of write performance is that if you plan on shooting long continuous bursts with the K-3, you shouldn't rely on the FluCard as a replacement for faster cards.  We recommend having a 45MB/s+ card in the SD1 slot for high-speed shooting.

Pentax DSLRs launched prior to the K-3 do not support UHS-I cards and have a write speed limit of around 30MB/s, which means that the FluCard would actually be a good fit for them performance-wise.  Of course, you only get wireless tethering ("Remote Capture") with the K-3 and newer bodies.

Wireless Transfer Speed

You can use a web browser to wirelessly download files from the FluCard instead of using a card reader.  According to its specifications, the FluCard operates up to a maximum theoretical wireless speed of 54Mbit/s (6.75MB/s).  In practice, as with virtually all wireless equipment, the file transfer speed is considerably slower due to protocol overhead, packet overhead, and potential transmission errors.

Using debugging software in Firefox we were able to measure the image download speeds through the FluCard's web interface down to the millisecond.  After taking a total of 10 measurements, the median transfer rate was 11.84 Mbit/s (1.48 MB/s), which is roughly one-tenth as fast as the read speed through a SD card reader.  In simpler terms, in our test scenario a 10MB JPEG file would take about six and a half seconds to download.  This is still more than fast enough to display the thumbnail view in Image Review mode in a timely manner, however, as the thumbnails are automatically scaled to a smaller size by the FluCard.

To speed up wireless viewing/downloading performance, it is possible to shoot RAW+ but reduce the JPEG size/quality via the camera's menu, which will result in a smaller filesize for quick viewing via the FluCard.  The corresponding RAW files for "keepers" can then be downloaded and/or processed later, either wirelessly or in the traditional way.  Note that RAWs can be stored to either SD1 or SD2 on the K-3; the only requirement imposed by the FluCard (when used for Remote capture) is that JPEGs are saved to it.

In our test, the FluCard was placed within one meter of our PC. The transfer speeds you will experience may vary depending on signal strength and your Wi-Fi adapter.

Remote Capture Latency

Using "highly specialized" test equipment consisting of a stopwatch, a computer screen, and a camera, we were able to measure the average latency of the FluCard's live view display to the nearest tenth of a second.  We took multiple snaps of the stopwatch in real life alongside the stopwatch as seen on the live view display and compared the two indicated times.  After 10 measurements, we found that the latency varied from 0.26s to 0.33s, with the median latency being 0.31s, or about one-third of a second.  We find this performance to be more than reasonable for everyday tethering.

FluCard Latency TestLatency test rig with actual time (below) and Remote Capture live view display (top)

What's a bit more annoying perhaps is that the live view display freezes while the camera is autofocusing (i.e. after you tell it to focus) and while the camera is writing to the memory card. A couple of seconds can pass until the live view display gets refreshed.


For the most part, our experience with the O-FC1 was trouble-free.  However, at times, the FluCard would not initialize when the battery in our K-3 was at 2/3 or 1/3 bars.  A few on/off cycles would fix the problem.  When the camera's battery got very low, the FluCard would sometimes reboot itself while in use.


We found the advertised maximum range of 7.5 meters to be fairly accurate (yet also optimistic) when we connected to the FluCard via a Samsung Galaxy smartphone.  At about 7 meters obstacle-free or 5 meters with a wall in the way, the wireless transfer speed would deteriorate significantly.  Take a few more steps back and the connection dies completely.  Fortunately, it is very easy to re-connect to the FluCard if you accidentally go out of its range, so we didn't find the limited range to be a problem in terms of stability.  This does mean, however, that you can't use the FluCard to control the camera on distant or moving rigs. 

Note that if you lose your connection to the card and have to re-connect to the network, you should press the refresh button on the screen to re-sync your browser window with the camera.


The FluCard generates a good amount of heat when used for prolonged periods of time.  Although we were unable to measure its exact temperature, we can say that it becomes hot enough to be unpleasant to touch.  The card's specified maximum operating temperature is 40° C / 104° F.

Technical Implementation

Note that this section gets very technical, so feel free to skip over it if you're not interested in how the FluCard is programmed. 

Both the Remote Capture and Image View modes of operation are implemented using a client-server web architecture, where a Javascript application running in your smartphone/desktop web browser is the client, and the FluCard is the server.  The FluCard relays any commands it receives from the client directly to the camera using its SD connectors.

The client application implementation is very simple under the hood: it simply polls the FluCard server at a set interval to obtain the latest data (i.e. the live view image) and to make sure the camera isn't powered off.  When you press the shutter release button in your browser, or any other button, the client application sends a HTTP request to the FluCard server, which then forwards the signal to the camera internally and transmits a response code back to the client.  Once the client receives a response, it updates what the user sees on the screen and/or asks the FluCard for additional information, such as a thumbnail of the latest photo captured.

Since data is never pushed to the client application (instead, it has to be requested), this architecture lends itself to a little bit of slowness, as we've observed with a number of the Remote Capture features.  On the other hand, it has a simple and flexible design, which makes it easy to add new features and make improvements.  Skilled programmers may also be able to reverse-engineer the protocol and create their own client application/hardware to control the camera.

Performance Verdict

The O-FC1 Pentax FluCard isn't the fastest SD card out there, but it certainly gets the job done.  Here are key performance metrics at a glance, as measured by our tests:

Write Speed 18 MB/s
Read Speed 10+ MB/s
Wireless Transfer 1.48 MB/s
Remote Latency 0.31s
Start-up Time ~30s
Range up to 7.5m

Since the card's tethering functionality is designed to be used in a studio setting and for transferring only one file at a time, we find its performance to be good enough; its stability is also satisfactory.  There is certainly room for improvement, and faster/better alternatives do exist for wireless file transfer, but no other SD card currently offers the Remote Capture feature enabled by the FluCard.  Options in the K-3 menu suggest that firmware updates can be installed directly to the FluCard, which means that it will possibly see performance and/or interface enhancements over time.

At the end of the day, the FluCard's performance suffices for casual use, but professionals currently shooting with other brands likely won't consider it a replacement for existing wired tethering options. PentaxForums +Pentax Forums @PentaxForums News | Reviews | Forum

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