The difference that matters
The Optoma ZK521ST-B throws a given image from closer (ratio 0.79 against 0.94). The Optoma ZK521ST-B costs $1,100 less at the prices we observed.
Side by side
| Specification | Optoma ZK521ST-B | LG ProBeam BU53RG |
|---|---|---|
| Brightness | 5,000 lm | 5,000 lm |
| Resolution | 4K UHD (3840 × 2160) | 4K UHD (3840 × 2160) |
| Native aspect | 16:9 | 16:9 |
| Throw ratio | 0.79:1 | 0.94–1.14:1 |
| Distance for a 10.5 × 8 ft 4:3 screen | 11′ 1″ | 13′ 2″ |
| Brightness on that screen | 45 fL | 45 fL |
| Light source | Laser | Laser |
| Rated life | 30,000 h | 20,000 h |
| Zoom | Fixed | 1.2× |
| Lens shift | Vertical 104–125% | Vertical ±50%, horizontal ±20% |
| Input lag | 16.7 ms (4K 60 Hz); 8.6 ms (1080p 120 Hz) | — |
| Price seen | $2,699 | $3,799 |
Highlighted rows differ. Figures come from each product's sources; room depth, distances and brightness are FOREference calculations using the same method for both.
Which should you choose?
Optoma ZK521ST-B
Choose the Optoma ZK521ST-B if you need to mount it close to the screen or price leads the decision.
LG ProBeam BU53RG
Choose the LG ProBeam BU53RG if you prefer its maker, seller or ecosystem — the published figures do not favour it.
Before you buy either
- Check the room: room size calculator and ceiling height calculator.
- Confirm what each seller includes — accessories, software trials and bundles change often.
- Read the limitations on each full reference page.
FOREference compares published specifications; we have not tested these products side by side. How we work · Disclosure