For a 12-foot-wide 16:9 image, the BenQ AK700ST needs a calculated lens-to-screen distance of about 8.28–9.96 feet. That range comes from its published 0.69–0.83 throw ratio. A 12-foot-wide square screen is a different geometry, so do not reuse the same distance.
The AK700ST and AH700ST share that published throw-ratio range. The optical calculations below therefore apply to both as starting points. The mounting hardware, final optical coverage and automatic fitting routine still need to be checked on the actual projector before the ceiling position is fixed.
Measure the screen surface, then the lens position
Record three measurements separately: the visible white screen area, the outside enclosure dimensions and the available lens-to-screen distance. The throw calculation uses the projected image, not the outside enclosure width. The mounting plate position is not necessarily directly above the lens.
For a native 16:9 image, multiply the image width by 0.69 and 0.83. The resulting interval is the published optical range. Keep the units consistent: feet produce feet, inches produce inches.
| Visible image width | Visible image height | Lens-to-screen range |
|---|---|---|
| 8 ft | 4.50 ft | 5.52–6.64 ft |
| 10 ft | 5.625 ft | 6.90–8.30 ft |
| 12 ft | 6.75 ft | 8.28–9.96 ft |
| 14 ft | 7.875 ft | 9.66–11.62 ft |
Distances are rounded to two decimals. These figures exclude the additional coverage needed for screen detection, any digital reduction, construction tolerances and model-specific image-size limits. They are planning calculations, not approved drilling coordinates.
Why a square screen can require much more distance
The projector's native image is 16:9. When a narrower active format uses the full optical image height, calculate the surrounding native image from that height:
Full optical width = active screen height × 16 ÷ 9.
Lens distance = full optical width × 0.69 to 0.83.
The unused sides of that native rectangle can fall outside the active picture. Digital fitting may reduce the active picture further. This distinction explains why multiplying only the visible width of a 4:3 or square screen can produce a mounting point that is too close.
| Active screen format | Active width × height | Full native optical width | Calculated lens range |
|---|---|---|---|
| 16:9 | 10 × 5.625 ft | 10.00 ft | 6.90–8.30 ft |
| 16:10 | 10 × 6.25 ft | 11.11 ft | 7.67–9.22 ft |
| 4:3 | 10 × 7.50 ft | 13.33 ft | 9.20–11.07 ft |
| 1:1 | 10 × 10.00 ft | 17.78 ft | 12.27–14.76 ft |
This table assumes full-height use of the native image without further digital shrink. It illustrates the optical constraint; it does not promise a successful automatic fit. Check the actual mode, screen detection pattern and final image size before committing to a mount.
For example, an available lens position eight feet from a 10 × 7.5-foot screen falls outside the calculated full-height 4:3 interval. Choosing a different ceiling bracket does not change that optical limit. You would need a different position, a smaller active picture or a shorter-throw projector.
Turn the distance range into a ceiling location
- Mark the lens position first. Lay out the screen centerline and the candidate lens distance on the floor. Translate that point upward only after checking the final image.
- Check the body around the lens. Allow for the projector chassis, mount arms, connectors, ventilation and access to controls. The optical coordinate alone does not describe the whole installation.
- Test the intended orientation. Select the appropriate projection mode and establish a square image with the projector securely supported in its intended orientation. Do not balance an inverted projector on an improvised support.
- Measure the required lens height. Verify it against the model's offset and installation guidance. Do not assume the lens belongs at screen-center height or that keystone can substitute for the correct mount height.
- Select the bracket and drop. Translate the tested lens height to a mounting-plate height using the projector and bracket geometry. Check the structural attachment and the bracket's load and compatibility specifications.
A simple height worksheet
If the ceiling is 108 inches above the floor and testing establishes a required lens height of 101 inches, the ceiling-to-lens difference is seven inches. That does not automatically mean a seven-inch extension pole: the bracket and the projector's lens-to-mount relationship occupy part of the distance.
Record the ceiling height, tested lens height, bracket attachment height and resulting extension separately. The example deliberately starts from a verified lens height; it does not derive that height from an assumed interpretation of the offset percentage.
Which ceiling mount and screws should you use?
BenQ's AK700ST Quick Start Guide identifies M4 ceiling-mount screws and the compatible CM00G3 mount. M4 specifies the thread size; it does not tell you the correct screw length through your particular bracket or spacer. Follow the projector and mount instructions together, and verify the AH700ST's own installation guidance if that is your model.
For another bracket, check model compatibility, arm alignment, supported weight, adjustment range and access to the projector's vents. A product listing that says “universal” does not answer all of those questions. The attachment to the building also needs to suit the actual ceiling structure.
Allow for Auto Screen Fit before drilling
The initial fitting pattern needs the projected image to extend beyond the screen edges while all 12 circle markers remain inside the contrasting border. BenQ specifies a border at least 2.4 inches (6 cm) wide for these models and recommends reducing ambient light during detection.
BenQ also gives specific recommendations for horizontally tilted installations: up to 10 degrees for 16:9 or 16:10, or 20 degrees for 4:3 or 1:1, with a recommended projection distance no greater than 7.2 feet (2.2 m) in that guidance. Those conditions concern the automatic fitting routine in a tilted setup; 7.2 feet is not the projector's universal optical distance limit. Prefer a square physical alignment and verify the routine in your exact arrangement.
If the image covers the screen but detection fails, use the Auto Screen Fit diagnostic sequence. Keep optical coverage and screen recognition as separate checks.
Check swings, shadows and cable access
Outline the complete projector and mount, not just a point on the ceiling. Check the intended hitting position for every golfer and handedness you expect to accommodate. Then test whether a golfer standing at address interrupts the projection beam. A geometrically correct image can still have an inconvenient shadow or put hardware in the swing path.
Route the signal and power connections so the mount can still be adjusted and the projector serviced. Confirm the intended computer output over the actual cable run before concealing it. Leave ventilation clear according to the model's instructions.
What if the required position does not fit?
If the optical range is too long, compare the LK830ST for a 4K option with a published 0.496 throw ratio, or the AH500ST for 1080p at 0.499. If the issue is an off-center mounting point rather than short distance, investigate the LK936ST lens-shift worksheet.
Bring the visible screen dimensions and your candidate lens coordinates to the simulator builder. Once the geometry works, compare the AK700ST and AH700ST for the resolution and setup features you need.
