Protective Filters

© Mike Spinak

First, I’d like to share a picture of the day. This picture, above, has nothing to do with the article below, but I hope you enjoy it.


Are protective filters a good idea for nature photography? Should you use protective filters?

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Here’s my admittedly unpopular, opinionated view on the matter:

Protective filters are filters which photographers put on the front of their lenses to protect the lenses’ front elements from damage, and not primarily for any effects of light filtration. Protection is by far the most common reason for purchase and most common reason for use of filters in nature photography. Many photographers, perhaps even the majority, keep them on their lenses all the time.

What gets put to use as a “protective filter” varies, but it is usually either a UV filter, a skylight or haze filter, or a warming filter of some variety… in other words, usually some kind of filter with a very slight reddish cast. Occasionally. it is a clear filter (also known as a window glass filter).

It sounds sensible to insure expensive lenses against damage with comparatively inexpensive filters, and those who profit from selling protective filters do their best to get that idea into the heads of beginning photographers. The reality is that their benefits are questionable, and usually not worth the disadvantages. There are a very few special occasions when protecting a lens’s front element could be a good idea (such as when photographing a sandstorm), but for general use, you’re probably better off without.

Here’s why:

Flare

Placing another piece of glass in front of the lens makes another surface that can reflect light back into the lens barrel, leading to more circumstances where flare occurs, and more extreme flare when it does occur.

Vignetting

Additionally, when a filter is put onto a lens, the filter’s ring also extends opaque material slightly forward of the front edges of the lens barrel, potentially blocking some light from entering near the edges of the lens. This can cause vignetting, especially if stacked with another filter, such as a circular polarizer.

Optical Degradation

Furthermore, no glass is optically perfect. To some minor degree, any extra glass will decrease light transmission, decrease contrast, increase aberrations, etc. (This is especially true if the filter is not mounted perfectly flat, such as may occur if it is not screwed on tightly enough.) As minor as this increase is likely to be with a high quality filter, why have this added imperfection at all, adding glass in front of a lens unnecessarily?

Color Casts

Moreover, skylight filters, haze filters, warming filters – most protective filters – cause detectable color casts.


In short, if lens designers and manufacturers had intended for a protective filter to be part of the optical design, they’d have built one in (as is the case on the Canon 600 f/4 IS L); and if they did not intend for one to be part of the optical design, then you’re at least slightly degrading your optics when you add one.

A Poor Bet

Besides the optical considerations, protecting lenses with filters is generally not as financially sound as it first appears. Good quality filters aren’t cheap, themselves, and if you buy one for each of your lenses just to keep on at all times as protection, the cost could be as much as getting two or three damaged front elements replaced. Factor this in against the rarity of actual incidents of damage to the front elements of lenses. I’ve been shooting extensively for a dozen years (without a protective filter), and have yet to damage the front element of one of my lenses. I know a number of serious photographers who have been shooting for longer than I’ve been alive (without a protective filter), but I don’t personally know anyone who has ever damaged the front element of a lens. So why pay the equivalent of the replacement cost several times over?

Risk of Exacerbating Damage

Additionally, their value in actually protecting lenses is questionable. While they can prevent lens damage in some cases, they can exacerbate an accident and cause damage in other cases. If the front of your lens is bumped hard enough to shatter the filter, then it will grind shattered glass into your front element, and shattered glass is much harder, sharper, and more damaging than almost anything else that might hit the front of your lens (such as a stick).

Unnecessary

Further, the protection that a filter provides to a front element is, for most situations, considerably less than the protection that a lens hood provides to a front element. Add in the facts that lens hoods usually already come with lenses as part of the original cost of purchase, and they reduce flare instead of increasing it, thereby increasing a lens’s optical quality instead of reducing it. Then note the ironic fact that, since protective filters increase flare, they almost necessitate conjunctively using lens hoods for flare prevention, and the use of a lens hood renders the protection provided by the filter nearly redundant.

So, while noting that there is some possible increased risk of lens damage in certain situations, I suggest not bothering with protective filters unless you have a specific need. Otherwise, travel lighter and less encumbered, and put the money into something more productive, like travel, or a new lens.


Another Day in Paradise – The Tatoosh Range from Paradise, Mount Rainier


All pictures and text are © Mike Spinak, unless otherwise noted. All pictures shown are available for purchase as fine art prints, and are available for licensed stock use. Telephone: (831) 325-6917.