A 1/2″ sensor has an active width of 6.4 mm. To image a 50 mm wide field, the lens has to run at 0.128X — that is 6.4 mm ÷ 50 mm. Everything below follows from that one number: the vertical field, the pixel resolution you actually get, and which real POMEAS lenses sit at this magnification.
| Sensor width | 6.40 mm |
| Horizontal FOV | 50 mm |
| Required magnification | 0.128X |
| Vertical FOV | 37.5 mm |
| Diagonal FOV | 62.5 mm |
| Camera resolution | µm per pixel (horizontal) |
|---|---|
| 1600 × 1200 (2 MP) | 31.2 |
| 2448 × 2048 (5 MP) | 20.4 |
| 2592 × 1944 (5 MP) | 19.3 |
Optical magnification is the ratio between sensor size and field of view. Written for the horizontal axis: magnification = sensor width ÷ required FOV width. Rearranged the other way, FOV = sensor width ÷ magnification, which is why a lens datasheet always quotes magnification rather than field — the field depends on which camera you bolt behind it.
Substitution: 6.4 mm ÷ 50 mm = 0.128X
| Model | Type | Magnification | Working distance | Distortion | Resolution |
|---|---|---|---|---|---|
| PMS-LTCM0118-261-G | Telecentric | 0.118X | 261mm | 0.01% | 31.85μm |
| PMS-LTCM0108-129-G | Telecentric | 0.108X | 129mm | 0.02% | 31.06μm |
| PMS-LTFM0106-468 | Telecentric | 0.106X | 468mm | 0.02% | 34.95μm |
| PMS-LTDC01607-120(Y) | Telecentric | 0.16X / 0.7X | 120mm | 0.02% | 25.81μm / 7.63μm |
| PMS-LTCM016-189 | Telecentric | 0.16X | 189mm | 0.01% | 25.17μm |
| PMS-LTFM017-416 | Telecentric | 0.17X | 416mm | 0.01% | 31.56μm |
Specifications are the values published on each product page. Blank cells mean the parameter is not published.
At 0.128X you are in in the low magnification range where telecentric designs dominate. The three lens families solve different problems: a continuous zoom lens covers a range of magnifications so one station can handle several part sizes; a telecentric lens holds magnification constant over the part height so a metrology measurement does not drift; a fixed focal lens is the simplest and usually sharpest option when the product never changes.
The models above publish working distances rather than a guaranteed envelope, because WD also has to contain the illumination. A ring light or a coaxial module typically eats 10–30 mm of that distance. Confirm WD with the light mounted, not on a bare lens.
0.128X. Divide the 6.4 mm sensor width by the 50 mm field you need: 6.4 ÷ 50 = 0.128X. The vertical field comes out at 37.5 mm, the diagonal at 62.5 mm.
Divide the field width by the pixel count. For 1600 × 1200 (2 MP): 31.2 µm/px and 2448 × 2048 (5 MP): 20.4 µm/px and 2592 × 1944 (5 MP): 19.3 µm/px this works out to see the table above. Remember that this is the pixel-limited figure — the lens still has to resolve it.
Yes if 0.128X falls inside a zoom range. No zoom model in the current catalogue reaches 0.128X; use a telecentric or fixed magnification lens instead. If your product mix changes every week, a zoom body saves the mechanical changeover; if it never changes, a fixed magnification lens is usually sharper and cheaper.
Only if you measure dimensions rather than merely detect defects. Telecentric optics keep magnification constant over the part height, so a 50 mm field measured at the top of the part matches the bottom. For presence checks and coarse alignment, a standard lens is fine.
Use magnification = 6.4 mm ÷ your FOV width, then check which catalogue magnification sits closest. Every step of that calculation is explained in the zoom lens FOV guide.
These pages carry the full model tables and method behind the numbers used here: TR-001: 16 optical performance test methods, motorized zoom lens selection guide, how zoom lens FOV is calculated, real working-distance values by model, 4K zoom lens models and per-step resolution. No published number here fits your part? Talk to our engineers: talk to an application engineer.
