---

[This post is part of our Designing Hardware for HD series. Be sure to check it out!]

There are still a few things that I haven’t touched here, in this HW for HD series. One of them is the camera. In the next few weeks I’ll try to cover some grounds in this area. But before I dive in to the issues at hand, I’d like to get you up-to-date with the basics.

This glossary that I supply here will assist you when the time comes to deal with camera issues, especially if you’re not familiar with camera-related technologies and terms.

You might also want to look into the “How Digital Cameras Work” essay in HowStuffWorks or try Camerapedia.org while you’re at it.

CCD

CCD stands for a Charge-Coupled Device. While that says relatively nothing, think about it as the sensor that captures the light and converts it into a digital representation.

CCDs usually differ in their size, which dictates the amount of light they capture, the size of lens that you will need and the amount of power they will require.

Focus

Cameras can either have a fixed focus or an automatic focus.

A fixed focus camera is one which has a set distance in which the image it captures will look good. Such a focus will usually be the one used by webcams or cameras on personal video conferencing systems, where the user is located at a “known” distance from the camera.

Automatic focus cameras are those that can change their focus to differnet distances depending on what they are pointed at. These will usually be used by cameras located in conference roomes where people can sit in different distances from the camera.

Zoom

Zoom can either be optical or digital. It allows zooming into people in a conference room or zooming out to see the whole settings.

Digital zoom will usually be available on fixed cameras, while the optical one will come as part of a PTZ camera. Which brings me to the next term…

PTZ

Some cameras are fixed while others can move around. Those that can move around are called “PTZ cameras”, or “Pan-Tilt-Zoom

Cameras”, as they can pan and tilt (move up and down and to the sides) and they can zoom in and out – mechanically. PTZ cameras usually rely on motors to move, in which case they make a bit of noise, or they can use magnetic mechanism, which is way too cool to be cheap enough to use.

PTZ cameras are the standard for room-system video conferencing endpoints, where people would like to control where the camera is pointed.

If it wasn’t clear enough, PTZ cameras cost more than fixed ones.

UPDATE: You can also check out our Wiki glossary term for PTZ.

Pixel Count

The “resolution” the camera is capable of. You are probably used to talk about 1.3, 5 or even 14 megapixels – that’s the pixel count – the amount of pixels that the camera’s sensor is capable of producing for an image.

The more pixels, the larger the CCD sensor will be, assuming the pixel size doesn’t change.

Pixel Size

A CCD sensor size is not only defined by the pixel count but also by the size of each pixel. And while intuitively, the smaller the pixel size, the larger the pixel count you can cram into a smaller CCD sensor – that’s not always a good thing: the smaller the pixel size, the less senstivity to light it will have.

Exposure

Exposure is the total amount of light allowed to fall on the photographic medium (photographic film or image sensor) during the process of taking a photograph. (from Wikipedia).

Usually, exposure is controlled by the shutter speed or the integration time in the CCD.

Gain

You can increase the CCD’s sensitivity to light. This is done by electrically amplifying the signal coming from the CCD. This process is called gain. Doing that causes the amount of noise in the captured image to increase dramatically.

Depth of Field

Put simply, this is the area in which the camera places everything within focus, without blurring information out of view.

Having only the relevant parts of an image “in focus” (i.e. within the depth of field) allows people to notice only what is relevant in a video call.

Backlight

Backlight is a real issue in video conferencing. It will usually manifest itself due to an open window in the room or fluorescent lighting in the back of the user. This will essentially “burn” areas within the image and make the whole setting a lot darker, taking out the details from the image.

In most cases, your users will simply need to change the settings – place the video conferencing system in a better location or just close the darn curtain. That said, some cameras will be capable of reducing the effects associated with back lighting, and this is something to consider.