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Neutral density filters are handy tools for photographers. By reducing the amount of light entering the lens, they allow the use of large apertures on bright days, or long exposure times to introduce motion blur. They’re also invaluable for videographers, enabling sufficiently slow shutter speeds to give a smooth rendition of movement.

Compared to fixed-density alternatives, variable NDs promise to be particularly useful. By rotating the front section of the filter, they allow you to change their strength and achieve a target shutter speed without having to carry multiple filters.

NiSi True Color Neutral Density filters Vario 1-5

Variable NDs work by using two polarisers, one in front of the other. When they’re perfectly aligned, the density is at its minimum; rotate the front one and it successively increases. But this can come with unwanted colour shifts and uneven darkening at high densities (so-called cross effects).

With its latest True Color ND-Vario filter, NiSi has aimed to minimise such problems. The firm says it has employed a polarising film that introduces no colour cast and effectively eliminates cross effects, even at the maximum 5-stop density. The filters are made from HUC (High Ultra Clarity) optical glass, with a smart two-tone frame design and an unusually pronounced grip around the edge.

I tested the 77 mm filter using the 60MP Sony Alpha 7R IV, with 16-35 mm f/4 and 24-105 mm f/4 lenses. In short, it delivers impressively on its promises. It brings no degradation of sharpness or detail, and no measurable colour cast when tested against a colour-checker chart. I detected a slight unevenness in density beyond 4 stops, but it’s only visible if you point the camera at an evenly lit surface, and shouldn’t ever be problematic in real-world use. Water simply rolls off the glass leaving no trace, while fingerprints wipe away easily using a microfibre cloth.

One thing you do need to keep in mind, though, is the polarisation effect. This is controlled by the angle of the front section, so adjusting the density can also affect such things as reflections. You may need to partially unscrew the filter for best results.

Verdict

NiSi’s True-Color variable ND works very well, doing exactly what it promises with no fuss. It’s optically excellent and comes in a comprehensive package. It also represents good value for money, especially given the sheer quality on offer.

At a glance

• Available in 40.5 mm to 95 mm thread sizes
• Blocks 1 to 5 stops of light
• True Color polarising film
• Cap and case included

Sizes and pricing

NiSi True Color ND-Vario filters are available in sizes from 40.5 mm to 95 mm, for 105,00 € to 220,00 €. Looking at some of the most popular diameters, 67mm costs 150,00 €; 72mm is 165,00 €; 77mm is 175,00 €; and 82mm, 200,00 €. This counts as good value compared to other high-end brands. Cheaper options do exist, but are likely to lack the same optical quality and feature set.

More Informations : www.nisioptics.com