For the mobile presenter, a zoom lens is a handy feature. The zoom lens lets you set up the projector on whatever table or desk happens to be convenient. With the zoom feature you can resize the image for the screen and audience that you have at the time. Conversely, if your projector has a fixed focal length lens, the only way to change the size of the projected image is to move the projector closer to or farther away from the screen. If you are going to use your projector in many different projection environments, a zoom lens may be an important feature for you to consider.
A manual zoom lens is generally preferred to a power zoom for several reasons. Manual zooms are easier and quicker to set up and focus. They are lighter, less costly, and there are fewer components to fail. Power zoom lenses on projectors in this class are essentially useless.
Most of the models in this category have manual zoom lenses. Among those that do, they vary slightly in zoom ratio; that is, the relative size of the smallest to the largest image that can be thrown from a given distance. The minimum zoom ratio in this group is 1 to 1.2 (noted 1:1.2), which means that the image can be resized by 20%. Sometimes this is referred to on spec sheets as the "zoom factor," which can be noted simply as "1.2x".
The maximum zoom ratio in this group is 1:1.3, which means the image can be resized by 30%. So the larger the zoom ratio, the more flexibility you have in setting up the projector to throw a given screen size from any given distance.
However, the difference between a zoom ratio of 1.2x and 1.3x is not enough by itself to choose one projector over another. Other performance factors will probably be more important in the selection process.
In this group of twenty XGA portables, all have manual zoom lenses except the Compaq MP-1600 and the Davis DP-X16, both of which have fixed focal length lenses. This is a shortcoming in these two models. But if you are willing to live with having to place the projector at a specific distance from the screen in order to create the screen size you want, these products offer other advantages.