Calumet Variable ND2-400 SMC 77 mm Ultra Slim Filter

Calumet Variable ND2-400 SMC Ultra Slim Filter Key Features:

• Adjustable ND2–400 range provides 1–9 stop light reduction
• Correct Colour technology maintains neutral white balance
• Japanese AGC glass offers high optical clarity with stable colour accuracy
• 28-layer multi-coating minimises reflections and reduces stray glare
• Hydrophobic and oleophobic coatings reduce marks for easier maintenance
• Scratch-resistant 6H hardness protects the glass surface during handling
• Ultra-slim 7.4 mm aluminium frame limits vignetting on wide lenses
• Raised frame edges for easier handling when adding or removing the filter
• Dual-thread design allows stacking with additional filters or accessories
• Supplied protective case keeps the filter secure during transport

What’s in the box?

• 1 x Calumet Variable ND2-400 SMC Ultra Slim Filter
• 1 x Protective Case

FAQs:

How does the Calumet Variable ND2-400 SMC Ultra Slim Filter control exposure?

The filter uses two rotating elements to vary light transmission between ND2 and ND400, giving users a 1–9 stop adjustment range. This design lets you fine-tune exposure without altering your chosen shutter speed, aperture, or ISO. It is particularly useful when maintaining a wide aperture for shallow depth of field or when extending shutter times for controlled motion in bright conditions.

Does the filter introduce colour shifts at higher densities?

The filter uses Correct Colour technology and Japanese AGC glass, both chosen for their stable optical behaviour across the full ND range. This design maintains neutral white balance and prevents the magenta or green colour shifts sometimes seen with variable ND filters. Users can move from ND2 to ND400 without needing to compensate for unwanted colour casts in post.

What advantages do the 28-layer coatings offer?

The multi-coating structure includes hydrophobic, oleophobic, scratch-resistant, and anti-reflective layers. These reduce flare, repel water and fingerprints, and improve scratch protection, so the filter stays cleaner and maintains optical quality for longer. This combination is invaluable for long exposures near water, where spray and fine droplets can otherwise mark the glass.

Will the 7.4 mm frame cause vignetting on wide-angle lenses?

The frame’s ultra-slim 7.4 mm profile is designed specifically to minimise vignetting on wide lenses while maintaining full thread strength. This slimmer structure keeps the filter close to the lens without intruding into the field of view.

Can I stack this filter with others?

Yes. The dual-thread design allows another filter or accessory to be attached to the front. When stacking, users should be mindful of focal length, as multiple rings can increase the risk of vignetting on wider lenses.

How resistant is the glass to scratches and field wear?

The filter uses Japanese AGC glass rated at 6H hardness, giving it increased resistance to minor abrasions during regular cleaning and outdoor handling. The protective coatings also help resist dust marks and contact with lens cloths, maintaining clarity over long-term use.