Many photographers go out UV filters on their lenses more-or-less permanently. Many others exercise not. Who is right? Should y'all buy UV filters (or articulate protective filters) for all your lenses?

This question is highly controversial amid photographers and the forums of DPREVIEW have seen many long discussions/arguments on the subject. The only matter we tin say for sure is that there is no definitive right answer. In this commodity, I volition try to explain my ain point of view and discuss the principal arguments for and confronting using UV filters. Most of these arguments apply equally to articulate protective filters.

I assume that the UV filter being used is of similar optical quality to the lens elements themselves. This is more often than not truthful for the best multi-coated filters from good manufacturers, merely may non exist truthful for the cheaper filters.

The filter blocks UV lite and removes the blue bandage from images taken in very bright sunny conditions

This statement is almost completely spurious for modern digital cameras. With old film cameras it was often necessary to use a UV filter because motion-picture show is extremely sensitive to UV low-cal. However, digital sensors are generally rather insensitive to UV, so the problem doesn't ascend to anything like the same extent.

Having said that, I have seen some prove that for certain lenses a UV filter can reduce the purple fringing caused by longitudinal chromatic aberration. The purple fringing of longitudinal chromatic aberration just occurs in particular circumstances and is not to be confused with the much more common coloured fringing caused past lateral chromatic aberration (well-nigh noticeable in the corners of the frame).

My personal view is that these furnishings are almost always insignificant and practise non provide a skilful enough reason for using UV filters on a regular basis with digital cameras.

The filter provides protection for the lens

At that place are two types of protection to consider.

Firstly, protection against damage caused by crude handling or dropping the lens/camera -
 I doubt if anyone has done a proper scientific study of this, but personal experience suggests that a mishap that damages the filter volition probably also damage the lens. I take seen no good bear witness that the presence of a filter significantly reduces the chances of seriously damaging the lens.

Secondly, protection against dust, dirt, smears and scratches on the forepart chemical element of the lens -  The presence of a filter on the lens certainly protects the front chemical element, as the dust, clay, smears and scratches go on the filter instead. Which is preferable?

The filter is apartment and easily removed, which makes information technology much easier to clean. Likewise, if it does get scratched, or gets then dirty that it is too hard to clean thoroughly, then information technology typically costs much less to replace than the lens.

On the other hand, many photographers argue that lenses practice not need cleaning very often and the chances of scratching the lens are very low, so it is better to salve your money and go without the filter.

The filter causes a loss of image quality

This is true in theory (except possibly in those rare cases of lenses that have been specially designed for utilise with a filter). Still, the loss of image quality is likely to be very small-scale in practise and so the real question becomes: Is the loss of image quality pregnant to me?

In trying to answer this, there are several different aspects of image quality that need to be considered:

Flare and ghost images

I utilize the term flare to mean an overall veiling of the image (or parts of the paradigm) due to stray calorie-free, while ghost images are secondary images of very bright lite sources, unremarkably badly out of focus and sometimes showing extreme coma, astigmatism and chromatic aberration besides.

Both flare and ghost images are caused by unwanted reflections or scattering from the various exposed surfaces inside the lens and camera body. The glass surfaces of all the lens elements will contribute, as will the glass surfaces of the filter. Typical modernistic lenses contain up to 15 or more elements, and the addition of one more than element (the filter) is not likely to brand much difference in about applied circumstances.

I accept never seen whatever convincing evidence that the presence of a adept quality filter increases flare to whatever noticeable extent with ordinary camera lenses.

However, there is a particular circumstance in which the presence of a filter may crusade noticeable ghost images. With some lenses, when used at full aperture (or nearly so), lite reflected from the sensor back through the lens may be reflected from the rear surface of the filter back into the camera producing a ghost image on the reverse side of the optical axis.  Ghost images of very bright lights are often visible in night shots taken with a very fast lens at full discontinuity if a filter (whatsoever filter, the type is irrelevant) is being used.

Although much fainter than the primary images, they can be very noticeable as they will be in focus if the lens is focussed at infinity and the lights causing them are in focus. These ghost images will disappear if the filter is removed, or if the aperture is reduced sufficiently (i.e. the F-number is increased).

Without a filter on the lens. Both this and the prototype below were taken at full discontinuity (f/1.7 for these images) with a standard lens.

With a UV filter on the lens. The greenish spots of light in the central portion of the frame are ghost images of some of the very bright floodlights. It is only a circular area around the centre of the image that is subject field to these ghost images. The diameter of this area reduces as the F-number is increased.

Both the above images are overexposed and this makes the ghost images more noticeable. Fifty-fifty so, it is only the brightest lights that produce ghost images that are vivid enough to be seen (and so merely when they occur against a relatively dark background). In daytime images, it is extremely rare for ghost images to be noticeable unless the sun is visible in the frame (and the air is clear then the sun shines brightly).

Notice that at that place is considerable flare almost the floodlights and this is the same in the ii images. The leftmost floodlight produces particularly strong flare which tin can exist seen both as a fuzziness and spreading of the floodlight itself and besides as a purplish brume which seems to surround the crane on the extreme left.

Loss of lite

I have never seen any convincing evidence that a good quality UV filter causes noticeable loss of lite through the lens. Indeed, that would non be expected as the filter is just ane additional glass element and most modern lenses already have at least seven elements and oftentimes twice that number or even more.

Loss of resolution

Again, I have never seen any testify that this is significant for a good quality filter on normal camera lenses. Good quality filters should have optically flat surfaces that do not disturb the direction of the light rays passing through the filter. If there is whatsoever slight variation from optical flatness (every bit may occur with a very cheap filter), the effect volition be most noticeable with extreme telephoto lenses considering of their magnifying consequence.

Conclusions

My evaluation of the evidence is that there is no really compelling show either to use a filter or not, except in a very few situations when it is better not to use a filter to avoid in-focus ghost images.

Personally, I do have UV filters on all my lenses and merely remove them in those very rare situations for which I know they may cause ghost images. My main reason for using filters is that I like to keep my lenses very clean and I feel more than confident in cleaning the filter than in cleaning the surface of the lens.

However, I recollect those photographers who cull non to utilise filters accept a audio example too!

The consequence of a muddied lens (or filter)

In comparing images taken with and without a filter, one thing I take noticed in doing the tests is that even a slightly dusty lens occasionally has a noticeably deleterious upshot on the prototype. This only occurs in extreme lighting weather such every bit when the sun is shining brightly and is inside the image frame, or very shut to information technology. Under such circumstances, low-cal scattered by dust particles on the front element of the lens or on the filter tin can significantly increase the stray light falling on the image.

Information technology's generally not worth worrying virtually a niggling dust on the lens (or filter). In normal circumstances grit on the forepart element has no visible effect at all. But, if you are shooting into a bright sun or other very bright lights, then it is a skilful idea to clean your lens (and filter) first.