The Quick Verdict
Get the BenQ LK830ST 4K Short Throw Laser Projector. It lists at $2,499, which is $200 under the Optoma at list. BenQ also names a golf picture mode for it and lists a 1:1 mode for square impact screens. The two share the same throw ratio, the same input lag and the same 3840x2160 resolution, so those two extras decide it. The Optoma ZK431ST-B is worth it if weight on the mount is the priority, since it's 1.63 lbs lighter. It's also the pick if you want a lumen figure backed by a stated measurement standard.
What They Have in Common
Both are laser, fixed-lens, short-throw projectors with a 0.496:1 throw ratio, a 16:9 native aspect ratio and 3840x2160 resolution. Both list 16.7 ms of input lag at 1080p 60Hz, and both include 4:3 among their stated modes. Neither maker publishes a warranty term for these models, so ask about that before buying either one.
Where They Differ
Throw and image size
Image width is throw distance divided by throw ratio. Both lenses are fixed at 0.496:1, so the numbers come out identical. From 10 ft back, each gives a 20.2 ft wide image. For a 10 ft wide image, each needs to sit 5.0 ft from the screen. Neither has optical zoom, so there's no range to play with. The distance you mount at sets the width, and that's it.
A 0.496 ratio is the difference between hanging the projector over the hitting area and hanging it way behind you. The number to measure is the distance from where the lens will sit to the screen. Optoma lists a 114% lens offset and no lens shift. BenQ doesn't publish a lens-shift figure for the LK830ST.
Screen shapes and golf mode
This is where they actually split. BenQ lists 1:1, 4:3, 16:9, 16:10 and 5:4 among its modes. Optoma lists 4:3, 16:9 and 16:10. A 1:1 mode isn't among Optoma's stated modes. That doesn't mean it can't do it, only that Optoma doesn't say it can. If your impact screen is square, BenQ is the one whose maker puts that shape on paper.
Golf mode works the same way. BenQ names a golf picture mode on the LK830ST. Optoma doesn't publish whether the ZK431ST-B has one, so that's a hole in the information, not a missing feature.
Brightness and lag
BenQ lists 4,000 lumens and doesn't state the measurement standard. Optoma lists 4,100 lumens to ISO 21118. Those two figures don't measure the same thing, so I'm not calling either one brighter. Input lag is a straight tie: 16.7 ms each at 1080p 60Hz.
Keystone, light source, size
BenQ's keystone is 2D with auto vertical, rated ±30 degrees vertical and ±30 degrees horizontal. Optoma lists ±15° each way, so BenQ's sheet shows more correction range. BenQ rates its laser at 20,000 hours. Optoma doesn't publish a life figure for this model, so there's nothing to line up against it.
The Optoma weighs 6.3 lbs against BenQ's 7.93 lbs. It measures 10.8 W x 4.3 H x 8.5 D inches, and the BenQ measures 10.99 x 4.74 x 9.03 inches. BenQ lists the LK830ST as a 2025 release and Optoma lists the ZK431ST-B as 2026.
Who Should Buy Which
Get the BenQ LK830ST 4K Short Throw Laser Projector if:
- Your impact screen is square and you want a 1:1 mode the maker actually lists.
- You want a golf picture mode named on the spec sheet.
- The lower list price matters: $2,499 against $2,699.
- The projector may end up slightly off-center, and you want the wider stated keystone range of ±30 degrees each way.
- You want a published laser life rating, 20,000 hours, on paper.
Get the Optoma ZK431ST-B if:
- The ceiling mount or bracket you're using is weight-sensitive and 1.63 lbs less makes a difference.
- You want a lumen figure tied to a named standard (ISO 21118) rather than an unstated one.
- You want a published lens offset figure (114%) to work out mount placement with.
- Your screen is 4:3 or 16:9 and you don't care about a golf mode. Both makers list 4:3 and 16:9, so the shape question drops out for you.
The Bottom Line
These two have the same lens, the same 16.7 ms of lag and the same 3840x2160 resolution. Both put out a 20.2 ft wide image from 10 ft back, because image width is throw distance divided by throw ratio and both ratios are 0.496. The BenQ lists for $200 less and is the one whose maker states both a 1:1 mode and a golf mode. Those are the two things a sim build asks about once throw is settled. My read is that settles it, unless the extra 1.63 lbs is a problem for your mount.