BenQ LS1LT1 Semi Long Zoom Projector Lens: Compatible with LU9750 LU9800 LU9915

BenQ Original Lens LS1LT1 Semi Long Zoom is a genuine optical accessory for BenQ installation projectors, belonging to the long throw category, with a throw ratio of 2.22:1 - 3.67:1. The original compatibility list covers 3 projector models; before installation, simply verify against the projector model and panel size — no adapter rings needed. The value of an original lens isn't a few extra rows of numbers on a spec sheet, but that it is calibrated at the factory to the optical path and mount of that series: once installed, the image circle, edge illumination, and focus travel all match design values, so you don't need keystone correction to compensate for image quality.

1. Lens Specifications

The above specifications are subject to the original manufacturer's specifications. For mechanical dimensions, flange focal distance, and mount type not shown in the spec table, please verify with us against your projector model; ordering based on similar model numbers alone carries the risk of incompatibility.

2. Converting Throw Ratio to Installation Distance

Throw ratio is the ratio of installation distance to image width. This original lens is a zoom lens (2.22:1 - 3.67:1), so a given image size corresponds to a range of distances; as long as installation falls within this range, focus can be achieved.

The above are clear distances from the lens face to the screen, excluding rear ventilation and cabling space behind the projector. Calculated for 16:10 aspect ratio; actual values are subject to on-site measurement and the original manufacturer's manual.

Image quality differs at the two ends of the zoom range: toward the near end the image is brighter with slightly softer edges; toward the far end the edges are sharper with slightly reduced brightness. Where space permits, we recommend landing in the middle of the range; after installation, first find the sharpest point on the focus ring, then fine-tune the shift.

3. Compatible Models (3 units)

The table below is taken from the original compatibility list; brightness and resolution are filled in from the model database, with "—" where unavailable, without speculation.

To check whether models outside the list are usable, send us photos of the projector nameplate and the existing lens for verification — same-generation platforms often share mounts, but the risk of ordering based on similar model numbers isn't worth it.

Throw Ratios Across Different Model Series

The same LS1LT1 Semi Long Zoom mounted on the following series does not have the same nominal throw ratio; selection should use the value for the actual series of your projector.

4. Three Things to Confirm Before Replacement

• Confirm the projector's chip and resolution. Original lenses are designed for specific panel sizes; with a different panel specification, the image circle cannot cover it, resulting in vignetting or edge light loss after installation.
• Calculate the installation distance first. This lens has a nominal throw ratio of 2.22:1 - 3.67:1; use the table in Section 2 to map it to your venue's dimensions. Prime lenses have no margin, and even with zoom you should leave 10–20 cm at both ends.
• Verify the mount and locking. Original lenses are calibrated to the mount of that series; after installation you must hear the lock engage. Crooked images and soft edges are mostly due to incomplete locking, not a problem with the lens itself.

If unsure, take one photo each of the projector nameplate and the existing lens nameplate and send them to us; verification against the actual hardware is the safest approach.