> I've been playing with the -E flag on the qcam, but I'm not sure what
> format and what values it will take. can anyone out there give me/us a
> brief desc of the -E flag and acceptable values?
From the man page:
Automatically adjust exposure. -E takes from one to
five parameters. They are, in order:
mode target-lum tolerance-lum std-target-lum std-
mode is an integer. Modes 0 and 1 examine the average
brightness of the picture, and adjust the brightness
until the average pixel luminance is in range. Mode 0
looks at the whole picture; mode 1 looks at only the
center ninth of the picture.
Mode 2 adjusts contrast to get the standard deviation
of the pixel luminance into range.
Ranges are specified in the next four parameters; if
they are not supplied, reasonable defaults are used.
From getopt's point of view, -E takes one parameter.
So if you're specifying more than one parameter,
enclose the parameters in quotes.
A similar description is in the CHANGES file, under the 0.8 delta
comments. I would love to make the docs clearer, if you can send
me a suggestion on what to put in the man page instead, I'd be
You're right that this is not very clear on valid ranges. Target-lum
has a useful range of 0-15 or 0-63, if you're using 4bpp or 6bpp
respectively. Tolerance should be a non-negative integer; small
numbers give more consistent pictures, but slow things down. The
Cam keeps exposing until the average brightness is
(target-lum)+/-(tolerance). Standard deviation should be a small
non-negative integer; the defaults are 10 (for 6bpp) or 2 (for
4bpp). Low standard deviation == low contrast. Tolerance for
standard deviation works the same as exposure tolerance.
Default values for 6bpp are 32, 0, 10, 0. Default values for 4bpp
are 8, 0, 2, 0.
- From: "Isaac D. Kishk" <email@example.com>