Sigma 17-40mm F1.8 DCvsSigma 18-50mm F2.8 DC DN
17-40mm F1.8 DC
17-40mm / F1.8
26-60mm equiv.
—
18-50mm F2.8 DC DN
18-50mm / F2.8
27-75mm equiv.
—
Which to choose
When the 17-40mm F1.8 DC suits you better
- Brightness1.3 stops brighter — better in low light and blurs the background more
When the 18-50mm F2.8 DC DN suits you better
- Weight260g lighter, so easier to carry
- Zoom rangeCovers 18-50mm in a single lens
These points are derived mechanically from the numbers. How a lens actually renders does not show up in specifications, so look at samples before deciding.
Size compared
- 17-40mm F1.8 DC115.9mm long × 72.9mm diameter
- 18-50mm F2.8 DC DN74.5mm long × 69.2mm diameter
Specifications compared
| Specification | Sigma 17-40mm F1.8 DC | Sigma 18-50mm F2.8 DC DN | Difference |
|---|---|---|---|
| Focal length (wide) | 17mm | 18mm | −1mm |
| Focal length (tele) | 40mm | 50mm | −10mm |
| Max aperture (wide) | F1.8 | F2.8 | 1.3 stops brighter |
| Max aperture (tele) | F1.8 | F2.8 | 1.3 stops brighter |
| Weight | 560g | 300g | +260g |
| Length | 115.9mm | 74.5mm | +41.4mm |
| Diameter | 72.9mm | 69.2mm | +3.7mm |
| Filter size | 67mm | 55mm | +12mm |
| Released | 2025 | 2024 | +1year |
| Stabilization | No | No | — |
| Weather sealing | Yes | Yes | — |
| Macro | No | No | — |
| Autofocus | Yes | Yes | — |
The difference column reads as 17-40mm F1.8 DC relative to 18-50mm F2.8 DC DN.The highlighted cell is the better side for that specification.
Check prices
17-40mm F1.8 DC
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18-50mm F2.8 DC DN
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17-40mm F1.8 DC in detail18-50mm F2.8 DC DN in detailAll RF mount lenses