Selecting the right lens will depend on the use. Three things are most important to consider: Front or rear projection, size of screen and distance to the screen.
First a few details. The brightness of the projector will be diminished by distance. This is not only because of light loss over that distance, but the amount of glass in a lens can also reduce the amount of light reaching the screen. Better quality glass in the lens will improve the level of loss, and also will improve the ability to gain a full focus and even field. This is another one of those areas where you get what you pay for. When you buy a projector with a permanently installed lens you will need to be sure that it will be able to project the distance you need in order to fill the screen.
A rear projection setup is usually limited in throw distance (or the distance to the screen). Short throw lenses are not common in smaller projectors unless they are specifically designed for the short distance. Some installed rear projection systems are designed with a mirror or combination of mirrors. This is to provide an increase in the throw distance as the image is projected back and forth against the mirrors. Registering these images can be tricky, so you may want to consider a professional projectionist to do the job. For very short throws the lenses are typically fixed in focal length, so positioning the projector is crucial. The shortest lenses typically require the projector to be at a right angle directly out from the center of the screen, both vertically and horizontally.
Front projection can either be across a distance, from below and in front of the screen, or hanging from above and in front of the screen. The lens is chosen for the distance, and based on the size of the screen. Most specifications with show a “throw to width” factor. This refers to the distance of the screen compared to the width of the screen. If the lens shows a factor of 1.2~1.8, then to get the closest distance to the screen you multiply the width of the screen by 1.2, and to get the maximum distance multiply 1.8 by the width of the screen. So if you have a 10’ wide screen then this lens would need to be between 12’ (10 x 1.2) and 18’ (10 x 1.8). This distance is from the front of the lens to the screen surface.
One of the leading projector manufacturers on the professional market is Eiki. Below is an example of available lenses and their specifications for an Eiki EIP-UJT100, which is a 14,000 Lumen projector with a 1900 x 1200 resolution. This projector is a higher end unit that is currently known for being one of the best bangs for the buck on the market. You will notice that there are a range of lens options that cover almost any installation situation; however the lens choice will often drive the overall cost of any projector. In the case of Eiki they offer an installation package that includes the projector, lens, spare lamps and a mount to hang the projector. For current pricing on this package or other projector options, contact us and we can work through your specifics.
You will note that there is a lens that is marked as a “standard lens”. This is typically the lowest cost lens, and if a projector comes with an included lens but has optional lenses, the standard lens is the one included.
On this chart you will see the list pricing for these items. As is the case with most anything in the retail world, the list price is the highest price that should be expected to be paid for an item. With equipment like this, most manufacturers hold their dealers to another standard, called MAP or Minimum Advertised Pricing. While it is not legal for them to set a price at which an item is required to be sold, they can require that the advertised price be limited to a certain level. Most often this will be the lowest price that you will find something available for sale on the internet, but not the lowest price available. Often you will have to speak to the dealer to find out the best price that they will offer.
These posts have not been an exhaustive list of information about this technology, but we like to inform our customers as best as possible when making a decision such as this. Obviously we have just scratched the surface in some ways, so we offer a service to help you in designing, contracting and/or installing systems. Typically this service will save you more money than you will spend with us, and if you utilize our services on the full project, then we can often credit all or part of the fee toward the purchase of your equipment.
Email us for special pricing available of all Eiki projectors and Lenses