Point and Shoot: They are not only very popular, they are the least expensive digital cameras. These cameras are fully automatic and usually don't provide you with a lot of creative control-that's why they are called "point and shoot." Because of the low resolution of many of these cameras, printed output is limited to about 4 x 6 inches or so. Despite this small size, the images are ideal for Web pages, e-mail attachments, and small reproduction sizes in newsletters and other documents.
Mega-Pixel: Positioned just above the point and shoot cameras is a family of cameras with over 1-million pixels. Generally, the higher resolution is combined with more advanced features such as through-the-lens (TTL) focusing and creative controls. This is one of the fastest growing categories of cameras because these cameras appeal to serious photographers who like to have creative control of their camera's settings and make prints up to about 8 x 10 in size.
Professional: If you have money to burn, you might cast your eye on the professional 35mm or APS SLR cameras that have been adapted to digital photography . These cameras often use 3 image sensors, one for each color so they capture great color and resolution. They also have at least 2-million pixels in their image sensors and usually many more . One huge advantage these cameras have is that most of the features (such as exposure controls) and accessories (such as lenses) designed for the film versions also work with the digital versions.
Digital Video: Normally we take one picture at a time with a still camera, or perhaps a few hundred at best with still cameras offering a video capture mode. However, it's also possible to select individual frames off a video tape. Shot at 30 frames per second, video captures 1800 images per minute. The ability to choose from such a vast array of images is tempting, but keep in mind that video has less resolution than most digital cameras. With the latest digital video cameras, you don't have to digitize frames because they are captured in a digital format. The lines here get very blurry because some digital still cameras are capable of capturing short video sequences and some digital video cameras can also capture still images.
Consider the following for satisfying the departments requireme nts -- try to stay away from the "nice to haves" -- they can increase the price drastically!!
Brightness - the most obvious difference between projectors is the lumen output. They are usually rated between 800 and 2300 ANSI lumens .
Color Management - projectors offer preset selections called Color Mode and Picture Management respectively. These presets are designed to optimize image quality for the type of material you are viewing. For example, presets are provided for different content such as movies, graphics, data and presentations. When you identify your source material, either by plugging into a specific connector or selecting a preset from the menu, the image attributes are automatically adjusted to optimize the image according to your choice. If you don't like a setting you can easily select another.
Connectivity - projectors provide similar connectivity. The items in common include: RGB input that allows a computer connection or a component video input; RGB monitor loop-through so you can plug in a monitor for local viewing; S-Video, Composite, component video, 1080i, 720p, 480p,and 480i.
The biggest connector difference between the projectors is that
some offer individual stereo audio input and output for S-Video, Video, and RGB/Component Video. Others offer one monaural input for Video/S-Video and one monaural input for RGB/Component video and no audio output. Some projectors use a RS-232 connector to allow remote control of the projector from a computer, while others offer a USB connector that allows you to connect your computer so the remot e control can serve as your computer mouse.
Contrast - t he higher lumen output tends to brighten whites and lighten blacks, so contrast remains the same between models, but the bri ghtness of the images are very different.
Scaling - Today's projectors automatically scale the source signal to fit the native resolution of the projector. If you can avoid scaling, do so. Matching the computer to the native resolution of a projector will always produce the best image when projecting data. Since computers allow a wide range of resolution settings, it is easy to change the resolution to match the projector. When viewing video, you generally don't have much control over scaling and the artifacts of a good scaler are hardly evident except in the movie credits.
Although great strides have been made by projector manufacturers to improve image scaling, it is marginal at best in computer mode. The problem is not hard to understand when you consider that the text that I typed in this article was originally Arial 10 pt and the characters were formed with columns and rows of single pixel widths. Going from SVGA (800 x 600) to XGA (1024 x 768) is a 28% increase in the vertical and horizontal resolution. It's very hard to take the pixels of my typed characters and add 28% of a pixel in both directions. Since pixels are indivisible, the solution is to gray scale and the result is fuzzy letters. If you must scale a data image, use larger text.
Keystoning - Your audience will expect your image to be rectangular. This means the projector must be at the right height and perpendicular to the screen. If not, the immediate result is a keystone affect where the sides of the image converge and the top and bottom of the image are of different lengths. You can generally fix this problem by either raising the projector or lowering the screen, but if that is not an option there are two types of solutions.
One method is lens shift where the optics can be shifted slightly to allow the image to be moved up or down to reduce or eliminate keystoning. This is the best solution, as it does not distort the content.
The other method is digital keystone correction where the image is electronically compressed to "square" the image. Of the two methods, lens shift is preferred because you do not lose content, but it is only available in about 15% of the projectors in the market today.
Digital keystone is now the preference of manufacturers because it is electronic, making it both economical and reliable.
Warranty - And last but not least is the Warranty. You hope you never need it, but you're paying for it so take the time to check it out.