4 in x 5.65 in Square ND1.5 (5 Stops) Filter - Ultra Slim Matte Box

In this review the K&F CONCEPT 4 in x 5.65 in Square ND1.5 (5 Stops) Filter is evaluated as a practical matte box accessory for videographers who need reliable exposure control. The bottom line: it is a simple, high-clarity ND32 that gives filmmakers more control over shutter speed and aperture without introducing color cast, and it is best suited to shoots that use a matte box system such as Tilta or SmallRig. The review highlights real-world handling, optical performance, and packing quality to help decide if this square ND filter belongs in your kit.

Key Features

• Matte box compatibility: Designed to mount on matte boxes and filter frames so it fits Tilta, SmallRig and mini matte box systems for flexible lens use.
• 5 stops light reduction: The ND32 density provides five stops of attenuation, allowing slower shutter speeds or wider apertures in bright conditions without overexposure.
• Imported HD optical glass: Double-sided polished glass produces clear images suitable for 4K and 8K video without noticeable softness or color shift.
• 0.2% ultra-low reflectivity: Very low reflectivity reduces unwanted lens reflections and helps prevent vignetting for higher contrast and richer detail.
• 28 multi-layer coatings: Nano coatings on both faces make the surface scratch resistant, waterproof, oil resistant and easier to keep clean during location work.
• Protective storage: The included leather filter bag provides simple protection for transport and keeps the filter safe in the bag or case.

Who It's For

The filter is aimed at cinematographers and serious hybrid shooters who already use or plan to use a matte box system and need a robust square ND to control exposure without sacrificing image clarity. It is especially useful for outdoor interviews, narrative shooting and controlled daylight scenes where five stops of reduction is the right tool for motion blur and depth of field control.

It is less appropriate for still photographers who prefer screw-in circular ND filters or for users who need variable ND functionality. Also, because it is a square filter meant for matte boxes, buyers should have or plan to buy a compatible matte box and frames rather than expecting to screw it directly onto a lens.

Pros & Cons

Pros

• High clarity HD optical glass preserves detail and is suitable for 4K and 8K video workflows.
• Low reflectivity and multi-layer coatings reduce flare, fingerprints and make cleaning easier on set.
• Matte box form factor makes the filter adaptable to many focal lengths when used in a professional filter holder.

Cons

• Square filters require a matte box or filter frame so they are not a screw-on, lens-specific solution.
• Fixed ND density limits flexibility compared with a variable ND when you need continuously adjustable stops.

Specifications

Filter type	Square ND (ND32)
Density	ND1.5 (5 stops)
Size	4 in x 5.65 in (10.16 x 14.35 cm)
Glass	Imported HD optical glass, double-sided polished
Coatings	28 multi-layer nanometer coatings, waterproof and oil resistant
Reflectivity	Approximately 0.2% ultra-low reflectivity
Compatibility	Designed for matte box systems (Tilta, SmallRig, mini matte box, filter frames)

Our Verdict

The K&F CONCEPT square ND1.5 (ND32) is a straightforward, well-made matte box filter that delivers neutral, low-reflection light reduction for 4K/8K video shooters who use filter holders. It represents good value for camera operators who need a fixed five-stop ND with durable coatings and clear optics, provided they accept the matte box workflow rather than screw-on convenience.

Frequently Asked Questions

Can this filter be screwed onto a lens?
No. This is a square matte box filter intended to be mounted in a filter frame or matte box rather than screwed onto a lens.

Will it change color balance?
The filter uses imported HD optical glass and double-sided polishing designed to avoid color cast, so it should not noticeably alter color balance for 4K or 8K capture.

Is the surface easy to clean on set?
Yes. The 28 multi-layer nano coatings make the surface more resistant to scratches, oil and fingerprints and simplify cleaning in the field.