BenQ LS1LT3 Long Zoom 2 Lens Review: LU9750, LU9800, LU9915 Compatibility

Genuine BenQ Lens LS1LT3 Long Zoom 2 is an optical accessory designed for BenQ business projectors. It features a long-throw design (Long Throw) with a throw ratio of 5.31:1 - 8.26:1. Its official compatibility list covers 3 projector models. Before installation, simply verify the projector model and panel size; no adapter ring workaround is needed. The value of a genuine lens lies not in the additional figures on a specification sheet, but in the fact that it is factory-calibrated to the optical path and lens mount of that projector series. Once installed, image circle coverage, edge illumination, and focusing travel all meet their design specifications, so there is no need to use keystone correction to compensate for image quality.

1. Lens Specifications

The above specifications are subject to the manufacturer's official specifications. For mechanical dimensions, flange focal distance, and mount type not shown in the specification table, please contact us with your projector model. Placing an order solely based on a similar model carries the risk that the lens will not fit.

2. Converting Throw Ratio to Installation Distance

The throw ratio is the ratio of the installation distance to the image width. This genuine lens is a zoom lens (5.31:1 - 8.26:1), so a given image size corresponds to a range of installation distances. Any installation distance within that range can be brought into focus.

These figures represent the clear distance from the front surface of the lens to the screen and do not allow for rear chassis ventilation or cable-connection space. They are calculated for a 16:10 image; actual distances should be verified on site and in accordance with the manufacturer's manual.

Image quality differs at the two ends of the zoom range: toward the near end, the image is brighter and the edges are slightly softer; toward the far end, the edges are sharper and the image is slightly dimmer. Where the venue allows, use the middle of the range. After installation, first find the sharpest setting on the focus ring, and then fine-tune the lens shift.

3. Compatible Projector Models (3 Models)

The table below is taken from the official model compatibility list. Brightness and resolution are populated from the model database; unavailable values are shown as “—” and have not been estimated.

To check whether a model not on the list can be used, please send us photos of the projector nameplate and the existing lens. Projectors based on the same-generation platform often share the same mount, but the risk of ordering based on a similar model is not worth taking.

Throw Ratio by Model Series

The nominal throw ratio varies by series when the same LS1LT3 Long Zoom 2 lens is installed on the series listed below. Select the value that corresponds to the actual projector series.

4. Three Checks Before Replacement

• Confirm the projector's imaging chip and resolution.Genuine lenses are designed for a specific panel size. If the panel specifications differ, the image circle cannot cover the full image, resulting in vignetting or edge light loss after installation.
• Calculate the installation distance first.This lens has a rated throw ratio of 5.31:1 - 8.26:1. Use the table in Section 2 to calculate the distance based on your venue dimensions. A fixed-focal-length lens offers no adjustment margin, and even a zoom lens should allow an additional 10–20 cm at both ends.
• Verify the mount and locking mechanism.Genuine lenses are calibrated to the mount of the corresponding projector series. You must hear the lens lock fully into place after installation. Image skew and soft edges are usually caused by incomplete locking rather than a problem with the lens itself.

If you are unsure, take one photo of the projector nameplate and one of the existing lens nameplate, then send them to us. Verification against the actual hardware is the safest approach.