Optoma BX-CTA11 Short Zoom Standard-Throw Lens Analysis for ZK1000, ZK1120, ZK1320

Optoma Genuine Lens BX-CTA11 Short Zoom is an official optical accessory for Optoma professional projectors. It is a standard-throw lens (Standard Throw) with a throw ratio of 0.78-0.90:1. The official compatibility list covers 3 projector models, so simply verify the projector model and panel size before installation—there is no need to make do with an adapter ring. The value of an OEM lens lies not in the extra lines of specifications, but in the fact that its optical path and mount are factory-calibrated for that model series: once installed, the image circle, edge illumination, and focusing travel all match the design specifications, with no need to rely on 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 distance, and mount type not shown in the specifications table, please verify them with us based on the projector model. Ordering directly on the basis of 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 genuine lens is a zoom lens (0.78-0.90:1), so a given image size corresponds to a range of installation distances, and the lens can be focused at any position within that range.

The values above are clear distances from the front surface of the lens to the screen and do not include space behind the projector for ventilation and cable connections. 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: near the short end, the image is brighter and the edges are slightly softer; near the long end, the edges are sharper and brightness is slightly lower. When the venue allows, the lens is best positioned near the middle of the range. After installation, first find the sharpest position using the focus ring, then fine-tune the lens shift.

3. Compatible Projector Models (3 Models)

The table below is taken from the official compatibility list. Brightness and resolution are populated from the model database; values that cannot be obtained are marked with an em dash (—) and are not estimated.

For models not on the list, please send us photos of the projector nameplate and the existing lens so we can verify compatibility. Platforms of the same generation often share the same mount, but it is not worth the risk of ordering based on a similar model number.

Throw Ratios by Projector Model Series

The nominal throw ratio differs across the model series below, even when using the same BX-CTA11 Short Zoom lens. Select the value according to the series of the actual projector.

4. Three Checks Before Replacement

• Confirm the projector imaging chip and resolution. Each genuine lens is designed for a specific panel size. If the panel specification differs, the image circle cannot cover the full image area, resulting in vignetting or edge light loss after installation.
• Calculate the installation distance first. This lens has a nominal throw ratio of 0.78-0.90:1. Use the table in Section 2 to calculate the distance for your venue. A fixed-focal-length lens offers no adjustment margin, and even a zoom lens requires 10–20 cm of clearance at both ends.
• Verify the mount and locking mechanism. The genuine lens is calibrated to the mount of that model series. After installation, you must hear it click into the locked position. A skewed image or soft edges are usually caused by an incompletely engaged lock, not by the lens itself.

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