22226RE: [SeattleRobotics] Low light cameras?
- Feb 1, 2005I've had very good experience with the Logitech QuickCam 3000 & 4000 and low
light conditions both for robotics and more traditional digital video
capture. The Logitech consistently outperformed much more expensive, high
end cameras (AKA the Sony Firewire series and a few others) for dealing with
low lux, even those with adjustable irises.
The Logitech cameras add most of their low lux capability from post
processing the image in the driver. I've been told by someone who's a
specialist in image processing that Logitech uses the "it's a grey world"
algorithm that assumes that a picture should be balanced out to an "expected
ratio" of grayscale. This might not work so well for the "shooting against
a background of white" scenario mentioned at the start of the thread.
We've been very pleased with the ability of the Logitech to pick out an
orange code in indoor and outdoor environments in a variety of lux
conditions. My wife had to spend some time tuning our software to figure
out what the range of RGB values are that correspond to "orange" under
different lighting conditions. The ironic thing is that if you take the
center numbers of the RGB ranges she came up with and write that color to
the screen it looks grey to a human eye. However this approach seems to
work very well for positive detection of orange without false detections, so
it must be something about the YUV components of "orange" that is more
detectable to a computer.
From: Alan King [mailto:alan@...]
Sent: Monday, January 31, 2005 4:29 PM
Subject: Re: [SeattleRobotics] Low light cameras?
Jay Prince wrote:
> Webcams are generally intended for indoor shooting, and should beOther way around, you're indoors at a computer at a generally fixed
> better for low light situations....
so they expect decent lighting not less, even good webcams are actually
at low light for the reasons given. And without post processing from the
Windows driver they're even worse. The CMUcam basically is a webcam, if
were much good at low light it'd already be working..
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