The Quick Verdict
Get the Optoma ZK431ST-B. It lists 3840x2160 resolution against the ZW350ST's 1280x800. Optoma publishes a 16.7 ms input lag for it at 1080p 60Hz. It also puts up the wider image from the same mounting spot. It lists at $2,699. The Optoma ZW350ST is the exception worth knowing about. It lists at $1,349, which is $1,350 less at list, and it's the one of the two with a golf picture mode Optoma actually names. That's the case for it where 1280x800 is enough resolution for the build. Check price at The Indoor Golf Shop →
What They Have in Common
These are two Optoma short-throw laser projectors with fixed lenses, no lens shift, and the same ±15° horizontal and vertical keystone. Each lists 4:3 among its modes. They're nearly identical in size, 10.8 x 4.3 x 8.5 in against 10.79 x 4.49 x 8.50 in. Optoma publishes no warranty term for either model.
Where They Differ
Throw ratio and image size
Image width is throw distance divided by throw ratio. The ZK431ST-B is 0.496:1, so from 10 ft back it puts up an image 20.2 ft wide. For a 10 ft wide image it sits 5.0 ft from the screen. The ZW350ST is 0.521:1. That gives an image 19.2 ft wide from 10 ft back, or a position 5.2 ft from the screen for a 10 ft wide image.
Neither has optical zoom or lens shift. Optoma lists offsets of 114% and 115%. That means the throw ratio alone decides where each one hangs, with no zoom range to adjust it. A ratio around 0.5 puts the projector out over the bay, a few feet off the screen, rather than at the back of the room. Measure the distance from where the lens would sit to the screen before you pick a mount point.
Screen shape
The ZK431ST-B is natively 16:9 and lists 4:3, 16:9 and 16:10 modes. The ZW350ST is natively 16:10 and lists 4:3 and 16:9. Both state a 4:3 mode. A square 1:1 shape isn't among the stated modes on either one, so check with Optoma before buying for a square impact screen.
Brightness, lag and golf mode
The ZK431ST-B is rated at 4,100 lumens to ISO 21118. The ZW350ST is rated at 3,600 lumens, and Optoma doesn't say which standard that figure follows. The two numbers don't line up against each other.
For input lag, the ZK431ST-B is 16.7 ms at 1080p 60Hz. Optoma doesn't publish a lag figure for the ZW350ST.
Golf mode goes the other way. The ZW350ST has one Optoma names. Optoma doesn't say whether the ZK431ST-B does.
Resolution, light source and the rest
The ZK431ST-B lists 3840x2160 and the ZW350ST lists 1280x800 (WXGA). My read is that's the gap the $1,350 at list is really paying for.
The ZW350ST's laser is rated for 30,000 hours. Optoma doesn't publish a life rating for the ZK431ST-B's laser.
The ZK431ST-B weighs 6.3 lbs and the ZW350ST weighs 6.61 lbs, so the ZK431ST-B is lighter by 0.31 lbs. Release years are 2026 for the ZK431ST-B and 2023 for the ZW350ST.
Who Should Buy Which
Get the Optoma ZK431ST-B if:
- Resolution is the deciding spec for the bay. It lists 3840x2160 against 1280x800.
- You want a published lag number to plan around. It's 16.7 ms at 1080p 60Hz.
- The mount point is fixed and you want the wider image from it. It gives 20.2 ft wide from 10 ft back, against 19.2 ft for the ZW350ST.
- The build uses a 16:9 or 4:3 screen and you'd rather have the newer model. It's from 2026, against 2023.
Get the Optoma ZW350ST if:
- You want a golf picture mode the maker names. It has one. Optoma doesn't say either way for the ZK431ST-B.
- A published laser life figure matters. It's rated for 30,000 hours.
- The screen is 4:3 or 16:9 and 1280x800 covers what the bay needs. At $1,349, it lists $1,350 below the ZK431ST-B.
The Bottom Line
The ZK431ST-B is the pick. It lists 3840x2160 resolution and a published 16.7 ms lag at 1080p 60Hz. Its 0.496 throw ratio gives a 20.2 ft wide image from 10 ft back. The ZW350ST lists at $1,349 and names a golf mode, which is a real reason to choose it where 1280x800 is enough. Neither lists a square mode, and neither has zoom or shift. Measure the lens-to-screen distance before buying either one.