Christie 121-123107-XX Long Zoom Lens Guide: Compatible with 13 Models

Christie Original Lens 121-123107-XX Long Zoom is an original optical accessory for Christie engineering projectors. It is designed for long-throw projection (Long Throw) with a throw ratio of 3.56-5.72:1. The manufacturer’s compatibility list covers 13 models. Before installation, simply verify the projector model and panel size; no adapter rings are needed. The value of an original lens lies not in the additional figures on a specification sheet, but in its factory calibration to the optical path and mount of that projector series. Once installed, the image circle, edge illumination, and focus travel all operate at their design values, eliminating the need to use keystone correction to compensate for image quality.

I. Lens Specifications

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

II. Converting Throw Ratio into Installation Distance

The throw ratio is the ratio of the installation distance to the image width. This original lens is a zoom lens with a throw ratio of 3.56-5.72:1. The same image size corresponds to a range of installation distances, and the lens can focus at any distance within that range.

The distances above are clear distances from the front surface of the lens to the screen and do not include space behind the projector for cooling and cable connections. These figures are calculated for a 16:10 image; actual distances should be confirmed through on-site measurements and the manufacturer’s manual.

Image quality differs at the two ends of the zoom range: images are brighter with slightly softer edges toward the near end, while edges appear sharper and brightness decreases slightly toward the far end. Where the venue allows, use the middle of the range. After installation, find the sharpest position using the focus ring, then fine-tune the lens shift.

III. Compatible Models (13 Units)

The table below is taken from the manufacturer’s compatibility list. Brightness and resolution are populated from the model database; unavailable data is marked with an em dash, and no assumptions are made.

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

Throw Ratios by Model Series

The nominal throw ratio of the same 121-123107-XX Long Zoom lens varies by projector series. Select the value based on the series of the actual projector.

IV. Three Checks Before Replacement

• Confirm the projector chip and resolution. Original lenses are designed for specific panel sizes. 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 nominal throw ratio of 3.56-5.72:1. Use the table in Section II to calculate the distance for your venue. A fixed-focus lens offers no adjustment margin, and even a zoom lens should have 10–20 cm of clearance at both ends.
• Verify the mount and locking mechanism. Original lenses are calibrated to the mount of the corresponding projector series. You must hear the lens click into its locked position after installation. A skewed image or soft edges are usually caused by an incomplete lock 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 nameplate. Verification against the actual hardware is the most reliable approach.