Christie 121-128102-XX Fixed Ultra Short Throw Lens Guide for LWU755-DS and LWU900-DS

Christie OEM Lens 121-128102-XX Fixed is an OEM optical accessory for Christie professional projectors. It is an ultra-short-throw (Ultra Short Throw) lens with a throw ratio of 0.38:1. The manufacturer compatibility list covers 2 models. Before installation, verify the projector model and panel size; no adapter ring workaround is needed. The value of an OEM lens lies not in the additional specifications, but in the fact that it is calibrated at the factory to the optical path and lens mount of that projector series. Once installed, the image circle, edge illumination, and focus travel all meet their designed values, eliminating the need for keystone correction to compensate for image quality.

1. Lens Specifications

Brand	Christie (Christie)
Lens Model	121-128102-XX Fixed
Throw Ratio	0.38:1
Product Type	Ultra Short Throw
Compatible Models	2 models
Warranty	12 months; after-sales service is available for damage not caused by the user, subject to the date on the shipping invoice

The above specifications are subject to the manufacturer specifications. For mechanical dimensions, flange distance, and lens mount type not listed in the specifications table, please contact us with the projector model for verification. Ordering solely based on a similar model carries the risk that the lens will not fit.

2. Calculating Installation Distance from Throw Ratio

The throw ratio is the ratio of the installation distance to the image width. This OEM lens is fixed-focus (0.38:1), so the installation distance varies linearly with the image size and offers no room for adjustment. Accurate measurements are required before installation.

Image Size	Image Width	Required Installation Distance
100 inches	2.15 m	approx. 0.82 m
120 inches	2.58 m	approx. 0.98 m
150 inches	3.22 m	approx. 1.23 m
200 inches	4.30 m	approx. 1.63 m

The above figures represent the clear distance from the front surface of the lens to the projection screen and do not include clearance for rear housing ventilation and cable connections. They are calculated for a 16:10 aspect ratio; actual values are subject to on-site measurements and the manufacturer manual.

3. Compatible Models (2 Models)

The following table is taken from the manufacturer compatibility list. Brightness and resolution are populated from the model database; unavailable information is shown as “—”, with no assumptions made.

Model	Brightness	Resolution
LWU755-DS	7000 lumens	1920x1200
LWU900-DS	8000 lumens	1920x1200

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

Throw Ratios by Projector Series

The rated throw ratio varies when the same 121-128102-XX Fixed lens is used with the series listed below. During lens selection, use the value for the projector's actual series.

Projector Series	Throw Ratio
—	0.38:1

4. Three Checks Before Replacement

• Confirm the projector's imaging chip and resolution. Each OEM lens is designed for a specific panel size. If the panel specifications differ, the image circle cannot cover the full image, resulting in vignetting or light loss at the edges.
• Calculate the installation distance first. This lens has a rated throw ratio of 0.38:1. Use the table in Section 2 to match the dimensions of your installation site. A fixed-focus lens offers no adjustment margin; for a zoom lens, allow 10–20 cm at both ends of the zoom range.
• Verify the lens mount and locking mechanism. The OEM lens is calibrated to the lens mount of that projector series. After installation, you must hear the lock engage. Image skew or soft edges are usually caused by incomplete locking rather than a problem with the lens itself.

If you are unsure, send us one photo each of the projector nameplate and the existing lens label. Verification against the physical items is the safest approach.