lens-dat

lens with infrared

inside of the lens

lens and oil

How mineral oil affects lens materials

● Glass elements

Mineral oil does not damage glass. No dissolving or warping.

● Optical coatings (multi-coatings)

Mineral oil does not chemically attack coatings, but it can leave an oil film.
This causes:

  • lower contrast
  • foggy look
  • ghosting

● Optical glue (UV glue / epoxy glue)

Most lens groups use epoxy-based optical cement.

  • Short-term contact: usually safe
  • Long-term soaking: may soften, yellow, or release stress

● Plastic parts (ABS, PC, nylon)

Usually stable in mineral oil.
Some plastics may swell after many months.

lens tuning

Six keys to maintain clarity after oil immersion

  • Use oil with a consistent, stable refractive index
  • Avoid any trapped air bubbles
  • Ensure every lens surface is completely clean
  • Lens elements must not be decentered or loose
  • Use oil that stays clear long-term (no discoloration or precipitation)
  • Re-focus after oiling to restore optimal imaging

🔹 Step 3: Loosen M12 lens lock

Most M12 lenses have a locking ring / small set screw.

Loosen just enough to rotate the lens for focus adjustment.

Keep the lens barrel supported.

🔹 Step 4: Adjust focus

Rotate the lens barrel slowly while observing the live camera feed.

Look for the sharpest image on your test target.

Zoom in on the LCD or PC and check multiple points (center + edges).

Fine-tune until center and corners are acceptably sharp.

Note: Oil can slightly change corner distortion, so prioritize center sharpness.

🔹 Step 5: Lock the lens

Tighten the M12 locking ring or set screw after final focus.

Avoid over-tightening (plastic threads may strip).

Make sure the lens does not move after locking.

camera lens

1G6P structure

Front (facing object)
────────────────────────────
1 × Glass lens (G)
6 × Plastic lenses (P)
Spacer rings
Long rear barrel (tube structure)
Rear protective window (your breakable piece)
M12 metal housing

in chinese 

前方（朝向物体）
─────────────────────
| 第1片：玻璃透镜（1G 的 G，即唯一一片玻璃） |
| 第2片：塑料透镜（P）                         |
| 第3片：塑料透镜（P）                         |
| 第4片：塑料透镜（P）                         |
| 第5片：塑料透镜（P）                         |
| 第6片：塑料透镜（P）                         |
| 第7片：塑料透镜（P）                         |
─────────────────────
| 后组保护片（可被损坏的那片，多叫 Shield 或 IR） |
| IR-cut filter（红外截止滤光片） *
| Spacer（间隔环）                              |
| Rear Barrel（后镜筒）                          |
─────────────────────
传感器

lens structure

1. Glass + plastic lenses

  • 1 glass lens in the front
  • 6 plastic lenses behind
  • Held by the long tubular structure (rear barrel)

2. Rear Barrel ("the long tube inside")

  • The long cylindrical module inside the metal housing
  • Holds and aligns all lenses
  • Controls internal light path
  • Not itself a lens

3. Rear Protective Window (the breakable piece)

  • Flat optical-grade glass or clear polymer
  • Always placed at the very back of the lens
  • Easy to remove or break
  • Does not change FOV or focus significantly
  • Only protects, not part of the lens formula

What Happens if You Remove the Protective Window?

✔ Image still works normally

Because it is not part of the optical design.

✔ More dust risk

Dust may settle on the last lens surface, causing spots.

✔ Last optical element becomes exposed

Plastic lenses scratch very easily.

✔ You may need to improve sealing

Especially if you plan to waterproof the lens.

🟥 (A) IR‑Cut Filter (Infrared Cut Filter)

Most M12 lenses have a small IR‑cut piece near the sensor:

  • IR‑cut (infrared cut filter)
  • Very thin
  • Looks like glass
  • Breaks if pressed
  • Shows a slight blue‑green reflection
  • Purpose: block infrared light to improve white balance and color accuracy

📌 Note: this is the most common “fragile small lens.”

If you break it:

  • Daytime colors shift toward pink / red
  • Night view becomes brighter
    (Many night‑vision cameras intentionally omit this filter.)

lens selection

Specifications - M12 小型 3.9mm 焦距、F1.0 大光圈镜头

  • Aperture (F No.): 1.0 ±10%
  • Focal length (焦距): 3.9 ±5%
  • Optical back focal length (Optical Back Focal Length): 3.94 ±0.2 mm (in air)
  • Mechanical back focal length (Mechanical Back Focal Length): 3.85 ±0.2 mm (in air)
  • Total lens length (TTL): 22.24 ±0.2 mm (in air)
  • Image circle (像面大小): Ø6.9 mm (MAX)
  • Lens structure (镜片构成): 1G6P — note: if the first element is a plastic lens, wipe with alcohol only up to 3 times
  • Mount (接口): M12 × P0.5
  • Lens-to-base clamp torque (镜头与底座螺纹配合扭力): 60–600 gf·cm
  • Minimum object distance (近摄距 / M.O.D): 2 m
  • Resolution (解像标准): 3840 × 2160 (8MP)
  • Suggested tilt tolerance of sensor packaging: ≤ 5' (minutes)
  • Weight: /

Field of view (FOV) — sensor size / sensor dimensions (mm)

  • 1/2.7" — 5.760 × 3.240 × 6.609
    • H / V / D (水平 / 垂直 / 对角): 88.1° / 47.5° / 104.1°
  • 1/2.8" — 5.568 × 3.132 × 6.388
    • H / V / D: 84.6° / 45.9° / 100.0°
  • 1/2.9" — 5.376 × 3.024 × 6.168
    • H / V / D: 81.3° / 44.3° / 95.5°

Optical characteristics (by sensor size)

  • Optical distortion:
    • 1/2.7": -34.0%
    • 1/2.8": -32.0%
    • 1/2.9": -29.0%
  • TV distortion (TVDistortion):
    • 1/2.7": -11.3%
    • 1/2.8": -10.4%
    • 1/2.9": -9.6%
  • Relative illumination:
    • 1/2.7": 40.6%
    • 1/2.8": 43.0%
    • 1/2.9": 45.5%
  • Chief ray angle (CRA):
    • 1/2.7": 11.2°
    • 1/2.8": 10.8°
    • 1/2.9": 10.5°

Operation

  • Focus (聚焦): Manual
  • Iris (光圈): Fixed
  • Environmental & Safety (环保 & 安全): RoHS

Notes:

  • The first optical element may be plastic; if so, clean carefully and limit alcohol wipes to 3 times.

specs

ref

Table of Contents

https://www.electrodragon.com