Christie 121-112105-XX Zoom Standard Throw Lens: LW551i LWU421 LWU501i LX501 LX601i

Christie Original Lens 121-112105-XX Zoom is a factory-supplied optical accessory for Christie engineering projectors, offering a standard throw with a 1.20-1.80:1 throw ratio. The factory compatibility list covers 5 models. Before installation, simply verify the projector model and panel size—there is no need to make do with adapter rings. The value of an original lens lies not in the additional figures in a specification sheet, but in the fact that it is calibrated at the factory to the optical path and mount of that projector series: once installed, the image circle, edge illumination, and focus travel are all at their designed values, with no need to compensate for image quality using keystone correction.

1. Lens Specifications

These specifications are subject to the manufacturer's specifications. For mechanical dimensions, flange distance, and mount type not shown in the specification table, please verify them with us using the projector model. Placing an order solely because the model numbers are similar risks an incompatible fit.

2. Calculating Installation Distance from Throw Ratio

The throw ratio is the ratio of installation distance to image width. This genuine zoom lens has a 1.20-1.80:1 throw ratio, so a given image size corresponds to a range of installation distances, and the lens can focus anywhere within that range.

These figures represent the clear distance from the front of the lens to the screen and do not include space behind the projector for cooling and cable connections. They are calculated for a 16:10 image; actual values should be verified through on-site measurement and in accordance with the manufacturer's manual.

Image quality differs at the two ends of the zoom range: the image is brighter with slightly softer edges near end, while edges appear sharper and brightness decreases slightly near the far end. Where site conditions allow, use the middle of the range. After installation, first find the sharpest image on the focus ring, then fine-tune the lens shift.

3. Compatible Models (5 models)

The table below is taken from the manufacturer's official compatibility list. Brightness and resolution are populated from the projector model database; values that cannot be retrieved are marked as "—", with no estimates provided.

To confirm whether a model outside the list is compatible, send us photos of the projector nameplate and the existing lens. Platforms from the same generation often share the same mount, but it is not worth taking the risk of ordering based solely on a similar model number.

Throw Ratio by Model Series

When the same 121-112105-XX Zoom lens is installed on the series listed below, the rated throw ratio varies. Select the value based on the series of the actual projector.

4. Three Checks Before Replacement

• Confirm the projector imaging chip and resolution. Original lenses are designed for a specific panel size. If the panel specifications differ, the image circle cannot cover the full panel, resulting in vignetting or light loss at the edges after installation.
• Calculate the installation distance first. This lens has a rated throw ratio of 1.20-1.80:1. Use the table in Section 2 to calculate the required distance for your venue. A fixed-focus lens provides no adjustment margin, and even a zoom lens should leave 10–20 cm at both ends.
• Verify the mount and locking mechanism. The original lens is calibrated to the mount used on that projector series, and you must hear it lock into place after installation. A skewed image or 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.