Given the sheer enthusiasm for real-world optical effects in 2024, there’s a conspicuous absence of an entire class of filter which seems obvious when we think about it, but which has never existed. Or at least, if it does exist, we’d like to hear about it.

Many varieties of filter

There are many, many varieties of diffusion, mist and fog filters, things like the famous Pro-Mist or Schneider Classic Soft, which are substantially white. Any visible glow or contrast reduction they add takes its colour from the light in the scene. There are also filters described as black, which do different things but similarly avoid introducing any colour to the scene. There are also diffusion, mist and fog filters which are warm in tone. Tiffen recently added the antique variants of its suede, satin and pearlescent filter ranges, all of which add a subtle warmth. There have been Warm Black Pro-Mists and Warm Classic Softs for a while.

What there hasn’t been is any sort of corresponding cool version of most filters. It’s hard to prove a negative proposition, but if anyone’s ever found a Cool Pro-Mist or broad equivalent, something which creates blue or cyan glows, please mention it in the comments. It’s not as if we don’t like blue under other circumstances, of course. Zeiss spent a lot of time making the Supreme Prime Radiance lenses flare blue, which is a lot more interesting than some simpler designs which are entirely uncoated and therefore flare white. There are anamorphics with blue coatings specifically engineered to ape Panavision’s delicious designs of yesteryear, so blue flare is hardly an original idea.

In extremis, yes, there are some rather specialist filters which have created flare, glow or halation in colours other than neutral or warm. Examples are sometimes streak filters based on plastic fibre, like the those from Schneider, Optefex or NiSi, which are made using a dyed thread very similar to fishing line. They might be blue, or pink, or green. IB/E makes some beautiful, if very esoteric, filters based on natural materials or fabrics which are all kinds of colours. The effects are often fairly bold and these are not likely to be seen as appropriate for anything longer than a music video. There’s even one filter which produces a rainbow-coloured horizontal flare. Based on a diffraction grating, it was developed by Markus Förderer, ASC, BVK, for Bliss. IB/E now sells something similar.

To be as reductive as possible, what the warm-variant filters do is create glows, diffusion or contrast effects which are tinted toward yellow-orange-red; their effects lean toward a lower colour temperature (if they don’t push the entire scene that way). That’s perhaps sensible, given how many candlelit costume dramas and skin-toned cosmetics commercials there are in the world (although there’s perhaps an argument to have about correlation and causation, there). Still, humans are a famously wide variety of brownish colours. Fire is orange, and so are a lot of natural objects.

A logical choice

With that in mind, filters which lean toward the bluer end of the spectrum are a logical choice, if only because we’re used to thinking of things in terms of colour temperature where cool is the opposite of warm. In modern practice, cool might mean anything from steel-green industrial haze to moonlight that we imagine to be steely (though it really isn’t), so there’s room for a bit of variation. Other colours might be more niche; perhaps The Matrix could have used a Green Pro-Mist, and even a Pink Pro-Mist might find a home in a certain proportion of K-pop music videos.

There might be practical problems with the creation of blue-tinted filters. Many types of filter rely on metal flakes, and the world really only gives us two coloured metals, copper and gold. Vanadium is sometimes described as bluish, but the tint is almost invisibly subtle, and cadmium is similarly subdued – and toxic. A cool diffusion filter might rely on the iridescent blue powders made for cosmetics and car finishes.

If we’re allowed to ask for two things at once, let’s also consider that very few filter designs offer graduated colour. Usually, the number-one filter will generally create the same colour flare, just smaller. That’s also something which might be useful in various strengths. Put a warm filter on a scene that’s already warm, after all, and the result might be a bit over the top.

Setting up to manufacture a new filter using (possibly) new materials is not a trivial thing to do. Consistency and longevity is, obviously, crucial, so that a hypothetical number-one Cool Pro-Mist bought now will look the same as one bought in ten years. As such, the manufacturing process demands a lot of precision. Still, the world’s absolute fascination with optical effects over digital ones might make a company willing to turn out new ideas in filtration.