Exposure Via Software
by Gary Honis
One of the video capture softwares
I tried with the Fusion, IC CAPTURE, is being used by J-P Metsavainio
to take long exposure images of a few seconds in length. J-P estimates
the length of the exposures at between 1 and 4 seconds and it
allowed him to take images of planetary nebula by stacking multiple
images. IC CAPTURE does not give "fraction of a second"
exposure length readings that are provided by the original Logitech
capture software and most other video capture programs. Instead
it provides a numerical range of exposure levels between 0 and
-14. Another video capture program that handles the exposure settings
the same way as IC CAPTURE is NERO CAPTURE VIDEO.
Canicio of Astrosnap has
a working version of Astrosnap
Pro that allows high resolution (1280X960) AVI capture and
also long exposure control to 10 seconds.
This table shows the range of
exposure settings provided by the original Logitech software compared
to programs using the WDM (Windows Driver Model) interface such
as Astrosnap, IC Capture and Nero Capture:
10 Second Maximum Exposure?
Notice in the above table that
the Logitech driver has 15 increments of exposure settings ranging
from 1/1000 second to 1/5 second. The WDM third party capture
programs also provide 15 increments of exposure settings but they
extend the longer exposures beyond 1/5 second to 10 seconds. The
WDM third party capture programs change the exposure length by
doubling (2X) each subsequent exposure time. That being the case,
one would think that the (-14) setting would provide a 20 second
exposure (2 X 10 seconds), but when I try this setting, I still
get a 10 second exposure as per the (-13) setting. Maybe 10 seconds
is the longest exposure that the Fusion is capable of doing?
This shows the longest exposure
setting possible (1/5 second) using the original Logitech software:
This shows the longest exposure
setting possible (-14) using NERO CAPTURE VIDEO:
How do these "fraction of
a second" and "numbered" exposure settings compare?
To find out I took some images of a clock's second hand in a darkened
room. If the original Logitech software driver is used to set
the exposure length to its longest setting of 1/5 second, and
then the Logitech software is closed and the NERO software opened,
the exposure setting in NERO's "Video Device Properties"
window (above) is -8. An exposure setting of -8 appears then to
correspond to a 1/5 second exposure length.
Adjusting the exposure settings
below -8 using NERO results in longer exposures. To time the exposures
I took images of a clock's second hand as shown below. The second
hand did not move continuously but instead ticked from second
mark to second mark and became difficult to see on the longer
Nero at -8 Exposure:
Nero at -11 Exposure:Result: 1 second exposure
Nero at -12 Exposure:Result: 2 to 3 second exposure
Nero at -14 Exposure:Result: 8 to 10 second exposure
For the exposure above
at the -14 setting, only the minute hand can be seen, but I timed
the exposure by eye and it was repeatedly between 8 and 10 seconds.
Note that the actual exposure times in seconds using the Nero
software are close to but not exactly the exposure times listing
in the table above. Astrosnap Pro was used to determine the long
exposure lengths in the table. The actual exposure times have
been found to vary somewhat and can change after resetting either
the exposure or gain controls. This is the unstable nature of
the long exposure settings and I hope to find software that can
directly control exposure times reliably.
I thought that IC CAPTURE
software may have been summing shorter exposure images to produce
longer images, since its noise reduction feature appears to average
combine individual exposures. But since the NERO capture software
gives the same results, the Fusion is truly doing longer exposures
beyond the 1/5 second limit with the original Logitech software.
When I used IC CAPTURE during its trial period, it was very buggy.
NERO capture is behaving in a similar manner. While changing the
exposure settings, the display may freeze up for a few seconds.
Changing the exposure settings between -12 and -14 sometimes gives
strange results.....a brighter image...but shorter exposure. I
was able to adjust the exposure to -14 using NERO capture and
then closed NERO capture and opened PCCAM capture software which
retained the longer exposure setting. When I looked at the Exposure
setting in PCCAM, the "fraction of a second" reading
was "1/0 seconds" as seen below:
"1/0" equals infinity!!!
Hey, maybe this camera
can do longer bulb exposures using software?
The following 10 second
exposure dark frame was taken using Astrosnap Pro at room temperature:
The above dark frame
was reduced 50% in size. For the full frame version (1280X960)
Dark frame noise was
very consistent from frame to frame and the Fusion had been operating
for a few hours before dark frame capture.
Using third party software,
the Fusion can do longer exposures than are possible by the original
Logitech software. This agrees with the Fusion being able to take
higher resolution AVIs than are possible with the original software.
ASTROSNAP, IC CAPTURE and NERO CAPTURE, which enable the longer
exposures, are usable softwares but there is some quirkiness with
the exposure and gain controls when operating in the 10 second
An advantage of the
Fusion is its ability to do exposures of a few seconds in length,
without the need for a hardware hack or extra control cables,
which would be useful for autoguiding and taking exposures of
the the brighter deep sky objects.
peltier devices ready:)
Links to some of my other pages
on the Fusion:
For Part 1 of Fusion and Toucam comparison CLICK
test image results using IC Capture Software that provides higher
resolution video imaging CLICK
Solar H-Alpha and Lunar test image results using IC Capture Software
2 - Fusion and Toucam Compared - Saturn, Mars and Moon test images
Conversion instructions for Fusion Webcam CLICK
& Images of Sun in H-Alpha CLICK
MY MAIN ASTROPHOTOGRAPHY PAGE