At first glance the difference between USB and FireWire cameras does not seem to be very big. However, regarding practical applications in areas such as security, engineering, science and medicine these little differences become a deciding factor:

• FireWire devices allow an operating voltage from 8 to 30 VDC. The current consumption may be 1.5 A. USB devices are much less flexible. The operating voltage has to be 4.7 VDC while the max current is 0.5 A.

• FireWire devices hold their addresses after the system has been restarted while those of USB devices are reassigned. This is especially obstructive when using more than one camera.

• There are more than 50 internationally standardized protocols for FireWire devices. In the case of cameras transferring their image data without compression or an audio channel the protocol is DCAM/IIDC. USB cameras, in comparison, only come with proprietary protocols.

The cause of these differences lie in their history. USB is the successor of the RS232 interface. FireWire is a user friendly variation of busses such as SCSI, PCI, etc. When only using one camera, the differences are not usually important. But, for more demanding applications the possibilities of USB are very limited.

Please Note: This blog post is part of a series of five posts altogether.
The posts include: Part 1, Part 2, Part 3, Part 4 and Part 5.

White Balance

Use this parameter to vary the degree of red and blue in the image to achieve a lifelike color representation. The values can be controlled manually or automatically. The automatic white balance feature offers two operation modes:

Auto: the balancing algorithms affects the video stream continuously.
One push triggers only one pass of the adaptation procedure.

Simple multimedia cameras only provide one white balance parameter. Thus, increasing the degree of red leads to a decrease of blue and vice versa. High quality cameras offer two parameters and thus allow to adjust independently the degree of red and blue:

(The End.)

Please Note: This blog post is part of a series of five posts altogether.
The posts include: Part 1, Part 2, Part 3, Part 4 and Part 5.

Saturation

Use this parameter to adjust the color‘s saturation from monochrome to high color values:

Hue

Use this parameter to shift color values. Nevertheless, the relation between the colors remains:

(To be continued…)

Please Note: This blog post is part of a series of five posts altogether.
The posts include: Part 1, Part 2, Part 3, Part 4 and Part 5.

Sharpness

You may use this mechanism to enhance blurred images. Overdoing its application leads, however, to distortions:

Gamma

Gamma increases or decreases the middle graylevels. In other words, you compensate the non-linear behavior of picture tubes:

(To be continued…)

Please Note: This blog post is part of a series of five posts altogether.
The posts include: Part 1, Part 2, Part 3, Part 4 and Part 5.

Gain (Contrast)

Gain determines the amplification of the CCD’s output signal. This parameter may be adjusted manually or automatically. The amplification increases the contrast. A high gain, however, leads to noisy images:

Offset (Brightness)

The offset is added to the CCD‘s output signal. This parameter may be adjusted manually or automatically. Therefore, adding the offset increases all graylevels. Thus, the image looks brighter:

Auto Exposure und Exposure Reference

Auto Exposure determines whether the adjustment of the exposure time and the gain (see Shutter and Gain) is to be adjusted manually or automatically. You can use the parameter Exposure Reference to control the automatic operation. It compares the mean graylevel of the current image with the Exposure Reference. If these values are different, the exposure time as well as the gain are varied accordingly.

(To be continued…)