The Quick Verdict
Get the Optoma ZK431ST-B. Its 0.496:1 throw ratio puts a 10 ft wide image 5.0 ft from the screen. It lists at $2,699 against $3,799.99 for the LG, and it weighs 6.3 lbs to the LG's 21.4. It's also the only one of the two with a published input-lag figure. The LG ProBeam BU53RG is worth the extra $1,100.99 at list in one case: the projector has to sit 9.4 ft–11.4 ft back, and you want zoom and lens shift to work with when you mount it. Check price at The Indoor Golf Shop →
What They Have in Common
Both use a laser light source. Both list 3840x2160 resolution, a native 16:9 shape and a 4:3 mode. A 1:1 square mode isn't among the stated modes on either one. Neither maker publishes whether it has a golf picture mode. LG and Optoma both class their model as short throw.
Where They Differ
Throw and image size
Image width is throw distance divided by throw ratio. From 10 ft back, the Optoma ZK431ST-B has a fixed 0.496:1 lens and gives a 20.2 ft wide image. The LG ProBeam BU53RG has a zoom lens running 0.94–1.14:1, so from the same 10 ft it gives 8.8 ft to 10.6 ft wide, depending on where the zoom is set.
Flip it around and ask what a 10 ft wide image needs. The Optoma sits 5.0 ft from the screen. The LG sits 9.4 ft–11.4 ft from it.
LG labels the BU53RG short throw, and the number tells you what that means for the room. It mounts further back than short-throw models like the Optoma, so it needs a deeper room. A 0.496 ratio against 0.94–1.14 is the difference between hanging the projector over the hitting area and hanging it behind you. Measure the distance from where the lens would sit to the screen before you decide.
Screen shapes
Both makers state a 4:3 mode. LG lists 16:10, 16:6, 16:9, 21:9 and 4:3. Optoma lists 4:3, 16:9 and 16:10. Neither lists 1:1. That isn't the same as saying they can't fill a square screen. It only means a square mode isn't among the ones either maker states.
Brightness, lag and golf mode
LG rates the BU53RG at 5,000 lumens and doesn't say what standard that's measured to. Optoma rates the ZK431ST-B at 4,100 lumens to ISO 21118. Those figures don't measure the same thing, so I'm not calling either one brighter.
Optoma publishes 16.7 ms of input lag at 1080p 60Hz. LG doesn't publish an input-lag figure for the BU53RG, so there's nothing to compare it against. Neither maker says whether its model has a golf mode.
Mounting slack, build and the rest
The LG gives you more room to adjust after it's mounted. It has 1.2 optical zoom and lens shift of ±20% horizontal and ±50% vertical. The Optoma has a fixed lens with no lens shift and a listed offset of 114%. For keystone, Optoma lists ±15° horizontal and vertical. LG says it has no digital keystone correction but lists edge adjustment and warping at 4, 9, 15 and 25 points, plus horizontal and vertical image rotation.
LG says its 4K is pixel-shift. Optoma doesn't say how its 4K is produced. LG rates its laser at 15,000 hours, and Optoma publishes no light-source life for this model. LG's warranty reads "3 Year Limited / Up to 15,000 hours." Optoma publishes no warranty term for the ZK431ST-B.
The Optoma is 15.1 lbs lighter at 6.3 lbs and measures 10.8 W x 4.3 H x 8.5 D in. The LG weighs 21.4 lbs and measures 14.6 W x 6.1 H x 11.4 D in. The LG's release year is 2023 and the Optoma's is 2026.
Who Should Buy Which
Get the Optoma ZK431ST-B if:
- The projector has to sit close to the screen. It gives a 10 ft wide image from 5.0 ft back.
- You're hanging it from a ceiling and weight matters. It's 6.3 lbs to the LG's 21.4.
- You want a published input-lag number. Optoma lists 16.7 ms at 1080p 60Hz.
- Your screen is 4:3 or 16:10, both of which are stated modes.
- You'd rather keep $1,100.99 at list. It lists at $2,699.
Get the LG ProBeam BU53RG if:
- The projector has to sit further back. It needs 9.4 ft–11.4 ft for a 10 ft wide image and needs a deeper room to do it.
- You want slack in the mount. The 1.2 optical zoom and ±20% / ±50% lens shift give it to you, and the Optoma's fixed lens doesn't.
- You want a 21:9 or 16:6 mode, which only LG lists.
- A published warranty and rated light-source life matter to you. LG states 3 years and 15,000 hours, and Optoma publishes neither for this model.
The Bottom Line
My read is that mounting distance decides this one. Image width is throw distance divided by throw ratio. The Optoma gets a 10 ft wide image from 5.0 ft back. The LG needs 9.4 ft–11.4 ft and a deeper room for the same width. Add the Optoma's $2,699 list price, its 6.3 lb weight and its published 16.7 ms lag figure, and it's the default. The LG ProBeam BU53RG earns its $3,799.99 MSRP in a room deep enough for it, where zoom and lens shift matter.