Range of zoom lenses

The range between the image smaller and larger than a lens can be projected from a distance. For example, a range of 1.4:1 means that a picture from 10 feet with no zoom may be 14 feet with the entire zoom. On the other hand, an image diagonal of 10 feet to 15 feet with no zoom may still be 10 feet but 21 feet away with the maximum zoom (15 x 1.4 = 21 feet). The zoom lenses do not make the picture brighter, and the highest rank gives us the least amount of light.

Projector brightness is rated in lumens. A lumen rating indicates the overall brightness that a projector is able to produce. Lumens are actually dimensionless, so the lumen output of the projector is static and has nothing to do with the size of the image. However, the size of the image has everything to do with how bright the image you see is. For example, the larger the image is that you are trying to create, the brighter the projector will need to be if you want to overcome ambient light and still see a nice, vibrant image.

Some projectors come with a zoom lens which allows a little more leeway in how far a projector is placed from a screen to project a given sized image. This can be very useful for the projector on the move, so is worth considering. These zoom features are, however, limited to quite a small range.

For most people that are shelf mounting their projectors, they will find their zoom lens nearer to the middle of the zoom range, or further back. As a result the actual brightness will probably be a little less than we quote, since we measure with the zoom at mid range.