Seiko FA/ITS lens model numbers encode focal length, aperture, resolution, sensor format and mount. Decoding them lets you judge quickly — even without a datasheet — whether a lens fits your camera and application.
1. Typical model structure
A typical model breaks down into "focal length + optical traits + resolution marker + mount suffix". The common resolution marker is the MP series (megapixel-class resolution); mount suffixes include -C for C-mount and -C/T for switchable C / T (CS) mount.
| Segment (illustrative) | Meaning | Note |
|---|---|---|
| Leading digits | Focal length (mm) | e.g. 6 / 8 / 12 / 25; larger = narrower FOV |
| MP / MP2 | Resolution class | MP = megapixel class; higher number = more pixels |
| Aperture number | Max relative aperture (F) | e.g. F1.2 / F1.4; smaller = more light |
| -C | C-mount | Fixed C-mount |
| -C/T | Switchable C / T(CS) | Supports two back-focus distances |
The table is illustrative; exact meaning depends on each model's datasheet.
2. Resolution and sensor format
The MP series targets high-megapixel cameras. Verify that the lens resolution and format cover the camera spec; smaller pixels require higher lens resolution to avoid weak edge performance.
3. Focal length and field of view
Longer focal length means a narrower FOV and more magnification. Security uses 2.8–12mm commonly; machine vision derives focal length from working distance and FOV (see the calculation in Kowa lens selection).
4. FAQ
What is the difference between -C and -C/T?
-C is fixed C-mount; -C/T supports both C and CS (T) back-focus for more flexibility.
Does MP in the model mean telephoto?
No. MP only denotes resolution class, independent of focal length; use the leading digits for focal length.
Browse all models of Seiko FA/ITS lenses, or see the Seiko lens series overview.