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Image
Capture and Post-Capture Processing...Carefully follow the
instructions to install the software. Once the camera is installed
go to the Logitech "Downloads"
web page and download the latest drivers and software. The software
package that came with the Quick Cam® Zoom™ webcam allows
for totally automatic control of the camera settings or you can
set the camera settings manually.
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| Logitech
resolution controls. |
I
prefer to set the camera settings manually. Video clips recorded
at 640 x 480 pixels create large, bloated video files at only
15 fps video rate. The video clips look much better and the file
sizes are much more manageable at 320 x 240 pixel resolution.
Except in the most extreme of magnifications 320 x 240 pixel movies
will allow you to use the full 30 fps video rate, a decided improvement
in the appearance of the video clips.
Some
of the newer digital cameras being used for photomicrography have
digital video capability. I have considered using one of these
but have found several drawbacks to their use. Again, these cameras
are constrained to producing video clips at 15 video fps. The
amount of memory available on the digital memory cards is too
limited to allow large video files. This also limits the running
time of the video clip to about 15 secs to 30 secs on a really
large memory card. Because you can't remove the lens from the
digital camera you must use a widefield eyepiece as a relay lens
to avoid creating circular images in the video clips. I, personally,
find the circular images to be unattractive. With the typical
home computer there is essentially "unlimited" memory
compared to a digital camera. I have produced video clips as long
as 5 mins to 10 mins and then I edit out many smaller clips for
posting on my website.
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| The
4 most important webcam image controls. |
The
illustration at right shows the various exposure settings you
can make. I've indicated four settings of particular interest.
Gamma controls the overall contrast of the image. Shutter
Speed can be used to not only control exposure but it can
also be used to control the sharpness of the image. At lower magnifications
the shutter speed can be set faster and there will be less motion
blur in the video clips. Gain can really help out at higher
magnifications where exposures can become quite dark. Higher gain
settings will allow for brighter images but will create more "noise"
in the video clips. I always leave the White Balance setting
on Auto. Using
any of the other white balance settings does not help the overall
color balance. My raw video clips
are a bit too blue and too magenta overall and I really need to
add some color compensating filters to the light path to bring
the color to a more normal balance. In the meantime, I use a video
editing program that allows me to alter the overall color balance
of the video clips.
Focusing
is performed "on screen" using the computer monitor.
You have to experiment a bit with focusing technique. The image
on the screen changes just a little slower than expected because
of a small "lag time". Don't turn the focus knob on
the microscope as quickly as you normally would or you will constantly
overshoot the focus. Making videomicrographs will improve your
manual dexterity! Your first few video clips may be frustrating
as you learn to control the stage movements with one hand, focus
with the other hand, and clicking with the mouse when necessary.
Stick with it and these coordinated movements will quickly become
natural to you.
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| Vorticella
sp. imaged with a 40x objective lens and a 5x projection,
or "relay" lens. |
Throughout
this article I have written about using the webcam without a relay
lens allowing only the microscope's objective lenses to form the
image on the CCD array. If you need higher powers than what the
objective lenses alone can provide you can use the webcam in conjunction
with a photo relay lens or projection eyepiece. I have a series
of projection eyepieces in magnifications of 2.5x, 3.3x, and 5x
that I use in normal photomicrography. These lenses perform best
if the distance from the exit pupil of the projection lens to
the film plane (or CCD array) is 152 mm. When I need higher magnifications
than what I can obtain with my 40x objective lens I will attach
the webcam to the extension bellows that I use for standard photomicrography.
It is best to use the lowest power projection lens with the highest
power objective lens to maintain image quality. However, exposures
can become dim, the shutter speed of the webcam may have to be
set slower, and the gain control turned higher, all of which will
degrade the image quality somewhat. The image of the Vorticella
sp., at right top, was captured with a 20x objective lens
and a 2.5x projection eyepiece at a shutter speed of 1/300 sec.
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| Logitech
digital zoom and image positioning controls. |
You
can also use the webcam's digital zoom feature to increase image
magnification, if necessary (see photo lower right). The webcam's
software will allow you to increase the image magnification a
stated 2x, in 10 increments. However, keep in mind that there
will be a considerable loss of resolution as the webcam's software
will record fewer pixels and then use interpolation algorithms
to create the full 320 x 240 pixels contained in the video frames.
This also causes a great deal of pixel fluctuation and your movies
will look "squirmy".
An added feature with the digital zoom is the ability to shift
the view through the webcam using the tracking controls without
moving the subject with the microscope stage controls. If you
only need to nudge the image a tad you can add a little zoom and
then use the tracking controls to place the subject where wanted
in the frame. Again, keep in mind that image resolution will suffer.
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| A
very tiny amoeba captured in black and white at 640 x 480
pixels resolution utilizing a 40x objective lens and 10x corrected
eyepiece with bellows extension. |
Don't
overlook the fact that you can also record your video clips in
black and white rather than color. This is especially useful if
you are using high magnifications. Although not as impressive
on the screen as a color video clip, there can be several good
reasons for recording in black and white. If you use achromatic
objective lenses, as I do, you can increase the resolution of
the images somewhat by introducing a green filter in the light
path. The green filter will cancel some of the chromatic aberrations
inherent in achromatic objective lenses and will increase the
resolution of these lenses. Discarding color information will
also allow the use of higher shutter speeds resulting in better
CCD resolution. Finally, recording in black and white produces
much smaller video files. You can record longer clips without
draining the resources of your computer.
You
can use the Logitech Quick Cam® Zoom™ to capture single
images at 640 x 480 pixel resolution if you so desire. The button
on the top of the camera will allow you to shoot a single image.
Avoid using this button so as to not introduce vibrations in the
camera and microscope and make a single exposure using the software
controls instead. Once you have captured a single image the file
is saved as a .jpg file. You can use any image editing program
(such as Photoshop® or Paint Shop Pro®) to make any necessary
adjustments for color balance and contrast/density. I seldom make
single exposures with the webcam as I can get much better resolution
with my film camera. However, there are times when a single exposure
of a behavior or a single exposure to record an unexpected organism
becomes necessary. Obviously, both cameras cannot be attached
to my microscope at the same time so I will make the single exposure
and file it away for at least the record's sake.
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