The Imaging Source DFK 21AU04.AS
A great camera with a terrible name! Some would say the moniker of the DFK 21AU04.AS is useful because it describes the characteristics of the camera.
But it hardly trips off the tongue.
Housed in a metal cube, the DFK has a very solid feel.
One nice touch is a set of standard tripod screw holes along its base – useful if you want to fit a video lens and use it as a general-purpose colour video camera.
The camera’s driver is competent, while the control software’s installation procedure is extremely well thought out and gave us no problems whatsoever.
The capture software, called IC Capture, provides excellent control over all the camera’s functions via on-screen toolbars.
These can be turned off and on as required, but if you turn the majority of them on, the clean interface of IC Capture can rapidly become quite cluttered and we felt that this might confuse a beginner.
One area that isn’t particularly well explained is the use of the colour format and codec settings.
These dictate how the camera delivers its images and how they’re encoded into a movie file.
Different combinations have different effects and, confusingly, some let you see colour output on screen but save video in monochrome.
CCD sensors tend to be a little oversensitive to infrared (IR) light and this can upset colour balance and cause a loss of definition.
DFK cameras have an IR blocking filter fitted over the sensor to stop this problem. The equivalent DBK range includes the same cameras with no IR filter fitted.
The camera’s USB 2.0 connection allows it to generate 60 uncompressed 640×480 frames per second (fps).
Like most colour cameras, the DFK 21AU04 has a monochrome sensor at its heart, but each pixel site on the sensor is covered by a red, green or blue filter in a repeating pattern called a Bayer matrix.
A special process called ‘debayering’ analyses the relative intensities of the greyscale image filtered through the Bayer matrix to produce a full colour image.
If the camera has to do this itself, its maximum frame rate is limited to 30fps.
The IC Capture software gives you the option of turning debayering off in the camera, deferring the processing to your PC and allowing the camera to run at its full speed of 60fps. There are plenty of programs around that can do the debayering, including Registax.
We really liked using the DFK. Its comprehensive control software combined with great sensitivity made it an excellent tool for planetary, lunar and solar imaging.
The camera produced excellent results on Jupiter, showing the planet’s delicate colour variations well.
It also fared extremely well on the Moon and recorded the subtle lunar colour with ease.
Finally, it also gave great results when we imaged the Sun through an h-alpha filter, capturing the subtle surface mottling.
We’d recommend the DKF 21AU04 if you’re a beginner looking to move into more serious imaging, or you’re more experienced but don’t fancy messing around with a mono camera and filters.
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This review appeared in the January 2010 issue of Sky at Night Magazine