Optical vs digital zoom
Whether zoom is done with lens elements (optical) or by scaling the image into fewer pixels (digital).
- Standard
- ISO/IEC 21118 Table 1
- ISO 21118
- ISO 21118 required
Show the numbers
| Value | Metric | Imperial |
|---|---|---|
| Image width | 2.66 m | 8′ 9″ |
| Image height | 1.49 m | 4′ 11″ |
| Nearest lens position | 3.19 m | 10′ 6″ |
| Furthest lens position | 3.98 m | 13′ 1″ |
| Room depth needed (+35 cm chassis) | 3.54 m | 11′ 7″ |
How to compare it
Zoom type
Only optical zoom preserves resolution and brightness-per-pixel. Digital zoom counts as 'none' for placement flexibility.
Zoom ratio(×)
Maximum ÷ minimum throw (or image size). Derived from the throw range when it isn't stated.
1.0× is fixed. 1.1–1.3× gives small adjustments. 1.6× or more gives genuine placement freedom. 2.0× and up is enthusiast/install class.
Standard: ISO/IEC 21118 Table 1
Focal length(mm)
The lens focal length range.
Rarely useful to buyers, but it lets us cross-check the throw ratio against chip size.
Standard: ISO/IEC 21118 Table 1
F-number
Aperture ratio at wide and tele, e.g. F1.6–2.4.
A lower F at wide means more light. A larger F rise over the zoom range means more light loss at tele.
Standard: ISO/IEC 21118 Table 1
Marketing traps
- Zoom type: 'Zoom 50–100%' on lifestyle projectors is digital, so you're throwing away pixels.
- Zoom ratio: Brightness is usually rated at the wide (shortest-throw) end. At full tele, a 2× zoom lens can lose a noticeable share of light because the f-number rises.
Across the catalogue
Zoom ratio
9 of 24 projectors list it- Epson Pro Cinema LS120002.1×
- Sony VPL-XW7000ES2.1×
- JVC DLA-NZ82×
- Epson Home Cinema 23501.62×
- BenQ W58001.6×
Focal length
7 of 24 projectors list it- Epson Pro Cinema LS1200022.5–46.7 mm
- Epson Home Cinema 235018.2–29.2 mm
- BenQ W580016–25.7 mm
- BenQ X3100i17.02–22.21 mm
- Optoma UHZ5012.81–16.74 mm
F-number
5 of 24 projectors list it- BenQ W58002.1–3
- Epson Pro Cinema LS120002–3
- BenQ TK710STi2.53–2.73
- BenQ X3100i1.8–2.25
- Epson Home Cinema 23501.49–1.77
Deep cut
Zoom type. Digital zoom also changes the effective throw ratio: a 70% digital zoom at 1.2:1 behaves like 1.71:1 with 70% of the pixels.
Zoom ratio. When the f-number range is stated (e.g. F2.0–2.8), the light loss from wide to tele scales roughly with (F_tele/F_wide)². Check the lens spec to see what zoom costs.
F-number. Fast lenses let in more of the étendue budget but are harder to make sharp across the field. Big all-glass lenses (e.g. JVC's 100 mm class) exist for exactly that reason.
Terms on this page
Optical zoom ratio
Max ÷ min throw ratio, e.g. 1.6×. Optical zoom keeps all pixels, while digital zoom throws resolution away. ⚖ optics.zoom_ratio ↑, optics.zoom_type = optical | digital | none