Glass quality & color neutrality – ND & GND filters from FILTERFOTOGRAF®
Our neutral density (ND) and graduated neutral density (GND) filters are made of highly transparent optical white glass, are plane-parallel polished, and multi-coated on both sides. The result: maximum sharpness , true color stability , and a robust, easy-to-clean surface .
1) Material: Optical white glass
Our glass quality stands for very clear, color-stable optical glass with high transmission in the visible spectrum and minimal inherent color content. For precise image reproduction, the panes are polished plane-parallel – a crucial factor in ensuring that sharpness and microcontrast are fully preserved, even with high-resolution sensors.
- Transmission: very high in the VIS range, low self-reflection
- Plane parallelism: tight tolerances for a uniform focal plane
- Filter thickness: 2 mm rectangular filter – compatible with standard 100/150 mm holders
2) Coatings
- Multi-layer anti-reflective (AR): reduces surface reflections, increases contrast and minimizes ghosting.
- Nano topcoat: water- and oil-repellent; drops bead up and fingerprints are easier to remove.
- Scratch & cleaning resistance: robust top layer for everyday use, travel and harsh weather.
3) Filter structure with 30 layers of nano coating
Our ND and GND filters feature a double-sided multi-layer nanocoating with a total of 30 layers (hardened topcoats, water/oil-repellent topcoats, and anti-reflective coatings) on both sides of the optical glass core. This minimizes reflections, increases contrast, and makes the surface particularly durable and easy to clean.
4) Evidence from our tests
4.1 GND color test (chromaticity diagram)
Objective: To prove that the gray gradient does not create a color cast and that transitions remain natural.
Result: Measurement points close to the neutral center ; smooth, natural transitions without visible color shift.
4.2 ND test with ColorChecker
Result: Color values (e.g. on the neutral gray field) remain practically identical – the ND filter shows no visible color cast .
Setup: constant light, defined white balance, calibrated camera. Slight scatter is typical for optical systems and is within narrow tolerances.
5) Technical key data
| material | Optical white glass, plane-parallel polished |
|---|---|
| Thickness (rectangular filter) | 2 mm (industry standard; 100/150 mm holder compatible) |
| Coatings | Multi-layer anti-reflective (AR) + nano topcoat (hydro-/oleophobic), total 30 layers |
| Edge | Rounded & polished – safety and quality feature |
| Color neutrality | No visible color cast (confirmed by GND & ND tests) |
6) Practical advantages
- Maximum sharpness – no blurring, ideal for high-resolution sensors.
- Reproducible colors – RAW workflows remain consistent, reducing correction effort.
- Higher contrast – reduced reflections, clean gradients and richer blacks.
- Easy to clean – water/oil beads up and rolls off; ideal in rain, spray, and dust.
7) Care & Handling
- Hold the filter by the edges; do not tilt it when inserting.
- First blow off coarse dirt/salt or rinse with water, then clean with a microfiber cloth.
- Use individual sleeves or padded filter bags; store in a dry place.