# Cokin Pure Harmonie: filters for photographers who don’t like filters

Can Cokin's ultra-thin UV filter really be good enough to leave on a lens all the time without spoiling images?

Pure Harmonie filters are billed “the thinnest and lightest filters in the world” and are designed so “you won’t even notice when they are attached”. The Anti-UV filter in particular is described as “almost invisible”.

So you should be able to leave one of these on your lens, wherever you go, and forget about it, right? What about in the studio? We’re always interested in how things affect our camera’s performance. If you leave such a filter on your lens while shooting white backgrounds, for example, how much of a detrimental effect will it have on your photographs? And what about when you’re out and about, shooting outdoors?

It’s easy to think that a UV filter is a UV filter is a UV filter. What could really be different between two discs of essentially transparent glass? We decided to find out by comparing the £38 Cokin Pure Harmonie Anti-UV with a generic equivalent.

Firstly, notice how much thinner the Pure Harmonie filter is. When smoothly screwed on to the lens, the Cokin, which has a sturdy build to it, is barely noticeable. A more conventional filter sticks out much more. While you can stack both types of filters, you are more vulnerable to specular reflections and vignetting with the thicker kind.

Shooting on a white background with two lights, we compared the Cokin Pure Harmonie Anti-UV Multi-Coated filter with a cheap no-brand UV filter. Our camera was a Canon 550D with the 18-55mm f/3.5–5.6 kit lens, taking a 58mm filter. The results were interesting. While the cheap-o glass seems to weaken the blacks due to flare from the white background, the Cokin Pure Harmonie filter had no effect on contrast relative to using no filter at all.

Therefore, as a studio photographer, you have nothing to fear from leaving Pure Harmonie filters on your lens all day long, even when shooting high-key stuff. No matter how hard we tried, we couldn’t distinguish the Cokin photos from the no-filter ones. And we couldn’t fail to notice the effects of the generic filter, either, which in the worst backlit situations made images appear washed out, leaving less headroom for post-processing.

Outdoors, the Pure Harmonie filters are similarly capable of retaining a very high level of contrast. Andrew visited Leith with the filters to take some beautiful landscape pictures and did not disappoint.

In challenging backlit situations like shown below, there is minimal lens flare and no real indication that a filter has been used. A small level of chromatic aberration does appear but this is only noticeable at 100%.

Compare that to the generic UV filter (below), which seems to turn the lens into a much worse-performing piece of glass than it really is. An overcast sky seems to be all that’s needed for the cheap filter to protest too much glare and rob the image of a fair amount of contrast and saturation.

To conclude, Cokin’s claim “you won’t even notice that they are attached” is dead on, both mechanically and optically. But should you buy one?

The price on Amazon for a 58mm Cokin Pure Harmonie Anti-UV filter is £38 (twice that for the C-PL), compared to the retail price of the generic filter which was nearer to £3. So ten times more expensive, but is it ten times better? The cheap filter definitely isn’t worth bothering with, so yes. But using no filter at all costs you £0, and for digital photography stray UV light isn’t really a problem, which means you would buy these solely to protect the lens.

Is this protection worth the best part of £40? Maths time! If $X$ is the cost of keeping all your lenses filter-free, $x_i$ is the cost of replacement for a particular lens and $p_i$ is the probability you damage that lens so badly it needs to be replaced, then a set of these filters needs to be less than the expected cost of not owning them, $E[X]=\sum_{i=1}^\infty x_i \, p_i$ and be able to stop any of this damage taking place.

By this logic, there isn’t much point buying Pure Harmonie filters for your 18-55mm kit lens or 50mm f/1.8, since these lenses cost around £100, meaning you’d have to think there was around a 40% chance of damaging your lens beyond repair — and that a filter would prevent this — before they are cost-effective. On the other hand, for your brand new £1,900 70-200mm f/2.8 it makes much more sense (2.3% chance of undesirable, filter-preventable damage before buying Cokin pays dividends). Now, obviously real life isn’t as simple as this, but my point is that you have to strike a balance between the value of your lenses and the cost of protecting them. Or shoot film.

In the past on my lenses I have used Samyang UV filters, which are around half the price of a Pure Harmonie but not nearly as light or thin nor quite as good at preventing reflections. If quality, thinness and weight are really important to you, then go ahead and get one of these Pure Harmonie filters, put it on your lens and forget about it. But if you’d rather not shell out the best part of £40 then you might be better off with a chunkier, cheaper one. Just don’t get the no-brand filters.

Cokin filters are widely available. They are distributed in the USA by OmegaBrandess and sold at Amazon, Adorama, B&H and various other good photo stores. Thanks to Omega for arranging this review and thanks to Cokin in France for sending us the samples.

Andrew Gass contributed to this review.

David Selby
Based in Paris, France, David Selby is editor of Lighting Rumours, a part-time photographer and a quantitative analyst.
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