Colour imaging in bright conditions
This camera can give good colour imaging in bright conditions and at its maximum frame
rates. The maximum frame rate achievable depends on the spatial resolution setting and
exposure setting as well as whether raw YUYV camera output is used or whether MJPEG
compressed camera output is used (both options are available with the AF51) and there
are other limiting factors such as the speed of the host computer and the current state of
the USB 2.0 connection. Detailed specs will be presented later but, by way of example, for
raw YUYV output a maximal frame rate of 25 FPS is achievable at VGA resolution (640 x
480) and up to 3 FPS at full 5 megapixel resolution (2592 x 1944). If raw output is not
required then selecting the MJPEG compressed image stream will allow all resolutions
including full 5 megapixel frames to be streamed at a maximum rate of 30 FPS over a
good clear USB 2.0 connection in a computer with sufficient free processing power and
memory to handle this rate of data transfer.
The very best quality colour imaging with the AF51 – under any lighting conditions – is
achieved using the monochrome signal from the camera (the Y signal) and taking 3
pictures, each with a separate primary colour filter in the light path. For more detail about
this see chapter 7.
Medium low light level applications
The AF51 can also be used in medium low light level applications including dark field
microscopy and immunofluorescence. Achievable frame rates will be lower due to the
need for longer exposure settings and multi-frame integration (on the sensor chip) and
averaging (in software) for the lowest end of the useable light level scales. At the lowest
light settings the monochrome signal from the camera (the Y signal) will give the best
results as opposed to using its in-built colour capability. This is partly because the colour
signal processing inside the camera is subject to some artefacts that show up in low light
conditions. See chapter 7 for more detail.
General and macro photo / video recording
The AF51 can also be used for ‘ordinary’ photography and video recording using it’s in-
built lens i.e. not through a microscope or telescope (figure 2.2). Its lens has an auto-focus
option that makes it useful for filming objects that alter their distance from the camera and
it can also do macro photography of objects close to the lens.
For non-quantitative imaging the MJPEG compressed image stream of the camera can be
used that can give up to 30 FPS at full HD (1920 x 1080) resolution as well as even higher
resolutions such as 2K quad HD (2560 x 1440) and even up to the full 5 MP frame size
(2592 x 1944). Bear in mind that
the camera has no microphone so if you need
audio with your video you will need to arrange to record that with a separate
OptArc AF51 Camera Page 16 of 99 User Guide v1.02
