Modify a Webcam for Videomicrography

Part III: Image Capture and Post-Capture Processing
Text and photography copyright Thomas Webster 2003. All rights reserved.

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.

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.



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.

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.

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.


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.

Video Factory main control panel and image editing screen.

Although not essential, installing a video editing program can improve the appearance of your video clips. I personally use Video Factory 1.0 by Sonic Foundry. Unfortunately, Video Factory is no longer offered by Sonic Foundry. Sony Media Software has taken over support of Video Factory. Video Factory 2.0 may be purchased at very attractive prices right now and I highly suggest anyone purchase this program if you get very interested in producing video clips. This is professional video editing software with more capabilities than is probably necessary but it offers the capability of modifying the video clips and also saving the video clips in many different video formats.

Mostly I use Video Factory to color correct the video clips and also to set the final density/contrast of the clips. I will save long video clips to CD-R media but then "crop" the video clips into 10 second clips for posting on this website. My earliest attempts were converted to Real Player® video clips. I find that Real Player® offered better compression with the least loss of detail than Quick Time® offered. This is important as my web host does not support streaming media and, therefore, video files must be kept small enough for reasonable download times. Lately I've been experimenting with Windows Media Player® with very promising results. Windows Media Player® may soon become my format of choice.

That's all there is to it. You can go to "On Closer Inspection..." to view some of the video clips I have made with the Logitech camera. The clips are a mixture of Real Player and Windows Media Player, so be sure you have both installed on your computer. (End...)

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