G Dan Mitchell Photography

Sellers sell, and many buyers buy, UV (ultraviolet) filters for their DSLR and other cameras. The advantages are said to be twofold: some reduction of haze that is invisible to the human eye but which the sensor might register, and some protection of the front element of your lens.

On the other hand many photographers wouldn’t think of putting an extra layer of unnecessary glass in front of their lenses. They would rather accept the (rather small) possibility of a scratch on the front element of a lens than possibly reduce the quality if their images and/or they prefer to protect the lens by using a lens cap and lens hood.

I’m in the latter camp. I don’t own any UV filters and I can think of darn few situations in which I’d want to use one. (One possible exception being the use of some of Canon’s sealed lenses on which the seal is completed by adding a front filter – and here only if I were to use the lens in an extremely hostile environment, and with a fully environmentally sealed camera body such as that of the Canon 1 series.) My preference is to handle my camera and equipment relatively carefully, keep the gear in bags when not actually using it, use a lens cap, and to almost always use a rigid lens hood.

Level of Protection – Nothing can provide complete protection to a lens or other camera equipment. A filter can provide some protection and so can the cap/hood combination – either or both can offer some protection from objects striking the front element of the lens. With the filter the assumption is that a force that might damage a lens element will instead be absorbed by the filter, and even though the filter may be unusable the cost of a filter replacement might be less than the cost of replacing or repairing a lens. When using the cap/lens combination, the assumptions are that the cap provides even better protection when it is in place, that the cap will be on the lens when one isn’t taking a photo, and that the hood provides some additional protection in some situations.

To me this seems like a “six of one, half dozen of the other” question. Clearly the filter is the only option that provides a “cover” over the lens while shooting. On the other hand, a hood somewhat compensates for this to the extent that it extends in front of and to the sides of the lens. The lens cap is perhaps stronger than the filter, and can be handled more roughly when the lens isn’t actually on the camera, thus making packing a bit less fussy.

Dust on Lens – The filter will keep dust off the lens… by letting it collect on the filter instead! To the extent that you worry about a clean front element, you’ll need to clean the dust off the filter just as often as you would have cleaned it off the lens element, so there is no advantage to using the filter in this regard. (Experienced shooters will point out that dust on the front element probably has far less effect on your photos than you might imagine.)

I continue to be baffled by photographers who obsess over perfectly clean front elements and seem terribly concerned about the process of cleaning the lens – they often cite possible contamination of the front element as their reason for using a filter. I want to say, “Just clean the front element!” It is no more difficult to clean the front element of the lens than to clean a filter – you do it the same way. There is virtually no risk to the lens from cleaning it – lens glass is actually very tough material and won’t be damaged by normal cleaning. And it isn’t even necessary to keep your front element perfectly clean. A bit of dust on the lens is totally insignificant in a photograph. Don’t believe me? Next time you clean the front element do the following: Put the camera on a tripod, make an exposure before cleaning, don’t change anything, clean the front element, duplicate the exposure. No see if you or anyone else can actually detect any difference.

Convenience – The filter pretty much wins hands-down on this count. Assuming that you purchase a filter for each lens you own, once installed you can forget that the filter is there for the most part. If you use a filter instead of (as opposed to along with) a hood the smaller bulk of the lens/filter combination provides packing and carrying advantages. One complexity arises when you want to use other filters besides the UV. You must either replace the UV filter with, say, your polarizing filter (probably the best idea, for several reasons) or you’ll need to attach this filter to the front threads of your UV filter – in which case you may have vignetting issues if the assembly of the two filters extends far enough forward to enter the field of view of your lens.

With the cap/hood approach you’ll need to get in the habit of removing the lens cap, stashing it somewhere handy, remembering where you put it when you are done shooting, and remembering to put it back on the lens. Unless you can store the hood in its operating position on the lens you’ll need to attach it (whether you store it separately or reversed on the lens) and remove it when you are done. If you leave it on the lens it takes up more space and can make it awkward to pack your gear – this is especially true with the wide, shallow filters used on wide angle lenses. Less convenient, indeed. On the other hand, much of this becomes intuitive and second-nature after awhile, and what seems here like it might be a lot of trouble becomes fairly automatic.

Image Quality – A first question might be, “Does reducing ultraviolet light improve my photos?” The answer could be stated as, “Well maybe, but most probably not.” It turns out that, at least as far as I’ve been able to determine so far, modern DSLR camera/lens systems are not sensitive to UV light like cameras are/were. If so, and assuming that you are using modern lenses, there is likely to be no benefit from the UV filtering capabilities of these filters. (With this in mind, if you do decide to use a filter for “protection,” it might make more sense to use clear glass rather than paying extra for UV filtering you don’t need.)

A remaining question is, “Does a UV filter degrade my images in any way?” From what I’ve read, a few things are clear, while others are less so.

Filter quality does make a difference. Cheaply made filters can reduce image quality in several ways. On the cheapest filters, optical distortions in the glass can impact image quality, poor quality coatings can lead to contrast reductions and to reflections and excessive lens flare. If you care about getting the best image quality, putting cheap filters on your lenses is not an option.

The situation is more positive with high quality UV filters. Although they may not add anything to image quality, their potential for degrading the image is vastly reduced – to the point that in most cases any degradation is negligible, with one possible exception being the introduction of some additional flare in certain conditions and/or internal reflections from the back of the filter in others.

For those who care about image quality, one approach to using these filters might be to use only the very best UV filters and to consider removing the filter in situations in which flare could be an issue. Or, perhaps even better, only add a filter in truly risky environments.

Cost/Insurance – Here things become complex. If you are concerned (and you should be) that using cheap filters may lead to degradation of your images in at least some circumstances you’ll want the best filters you can buy. You certainly don’t want to spend over $1000 on a first-class lens, only to degrade the optical quality you paid dearly for by putting a piece of cheap glass in front of it.

A quick check of 77mm UV filters at B&H shows good filters costing between about $80 and $150. (77mm is the common thread diameter for high quality Canon L zooms.) Unless you are willing to forego the convenience advantage of the UV filter by moving a single filter between all of your lenses – assuming that they all have the same filter thread diameter – you’ll want one filter per lens. With four lenses in your kit you’ll spend between about $350 and $600 for good UV filters.

“Fine,” you might say. “That is less than the cost of replacing my most expensive lens.” True, but keep in mind that you are buying insurance, not absolute protection for your lens. In other words, if something happens that might damage your lens the filter will reduce but not eliminate the possibility of damage to the front element only. To make an admittedly imperfect analogy, would you invest half the cost of your car in insurance that would cover some types of damage to the front end only?

In order to justify the cost of a UV filter as “insurance” you need to figure out the relative value of several factors. (This isn’t a lot different than figuring out how large of a deductible to pay for on your auto insurance.) How likely is it that you’ll damage your lens? What percentage of the value of the lens will you pay to “insure” it with a filter? Of all the possible ways that your lens could be damaged, how many of them will be be affected by the use of a filter? Are you comfortable with other side effects of the filter including possible effects on image quality?

While there are objective answers to some of these questions, for others the answers may be relative to your personal approach to photography. Do you tend to handle your lenses carefully or casually? Are you able to absorb the costs of filters for all of your lenses, but unable to cover the cost of repairing or replacing a damaged lens? (That is a bit hard for me to imagine…) Is it a choice of a filter versus no protection or of a filter versus cap/hood? – and what value do you assign to the increment of additional protection you believe comes from choosing one over the other?

In some cases the answers might be clearer than in others. For example, it makes little sense to put a $100 UV filter on the very nice, $75 Canon 50mm f/1.8 lens. (It also doesn’t make much sense to put a cheapy filter on this lens and degrade its image quality.) It might make sense to put a $100 filter on a $2000 lens that becomes sealed with the addition of the filter if you use the lens in an extremely hostile environment – e.g. desert dust storms – and you work with sealed bodies.

Speaking of insurance, you do have regular insurance on your cameras and lenses, right? Regular insurance – the kind you pay for – will cover loss/damage to your lens that a filter can’t help with: damage to areas other than the front of the lens, theft, and so forth. It seems bit silly to spend hundreds of dollars on the minimal/arguable protection from filters and not spend a relatively small amount of money on real insurance that protects you far more thoroughly from loss/damage.

Bottom Line – As with many issues in photography, opinions vary. There are those who swear by UV filters for lens protection and those who believe that the protection that they might provide isn’t worth the cost – in funds or possible image degradation.

I can understand how one could decide either way, especially with photo retailers almost insisting that you get UV filters for your new camera/lens. For my part, I don’t use UV filters on my lenses, and I haven’t for years. I’m relatively careful with my gear, carrying camera and lenses in padded cases for the most part and using lens caps and hoods. However, I also regularly shoot in the situations that seem to concern many filter users: ocean spray, desert dust, light rain, snow, and so forth. While I cannot eliminate risk of damage, I think that the chances are relatively low – such that the substantial cost of high quality filters would be a poor investment. In addition, I’d rather not risk degradation of image quality, and I’m not about to spend the very large sum that it would take to put the best UV filters on all of my lenses.

Bottom line: If you ask me, I recommend not bothering with so-called “protective filters.” I recommend using lens caps and a hood.

G Dan Mitchell :: Dec.27.2007
Commentary, Equipment, Popular
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