Many photographers leave UV filters on their lenses more-or-less permanently. Many others do not. Who is right? Should you buy UV filters (or clear protective filters) for all your lenses?
This question is highly controversial amongst photographers and the forums of DPREVIEW have seen many long discussions/arguments on the subject. The only thing we can say for sure is that there is no definitive right answer. In this article, I will attempt to explain my own point of view and discuss the main arguments for and against using UV filters. Most of these arguments apply equally to clear protective filters.
I assume that the UV filter being used is of similar optical quality to the lens elements themselves. This is generally true for the best multi-coated filters from good manufacturers, but may not be true for the cheaper filters.
The filter blocks UV light and removes the blue cast from images taken in very bright sunny conditions
This argument is almost completely spurious for modern digital cameras. With old film cameras it was often necessary to use a UV filter because film is extremely sensitive to UV light. However, digital sensors are generally rather insensitive to UV, so the problem doesn't arise to anything like the same extent.
Having said that, I have seen some evidence that for certain lenses a UV filter can reduce the purple fringing caused by longitudinal chromatic aberration. The purple fringing of longitudinal chromatic aberration only occurs in particular circumstances and is not to be confused with the much more common coloured fringing caused by lateral chromatic aberration (most noticeable in the corners of the frame).
My personal view is that these effects are almost always insignificant and do not provide a good enough reason for using UV filters on a regular basis with digital cameras.
The filter provides protection for the lens
There are two types of protection to consider.
Firstly, protection against damage caused by rough 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 will probably also damage the lens. I have seen no good evidence 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 front element of the lens - The presence of a filter on the lens certainly protects the front element, as the dust, dirt, smears and scratches get on the filter instead. Which is preferable?
The filter is flat and easily removed, which makes it much easier to clean. Also, if it does get scratched, or gets so dirty that it is too difficult to clean thoroughly, then it typically costs much less to replace than the lens.
On the other hand, many photographers argue that lenses do not need cleaning very often and the chances of scratching the lens are very low, so it is better to save 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 use with a filter). However, the loss of image quality is likely to be very small in practice and so the real question becomes: Is the loss of image quality significant 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 use the term flare to mean an overall veiling of the image (or parts of the image) due to stray light, while ghost images are secondary images of very bright light sources, usually badly out of focus and sometimes showing extreme coma, astigmatism and chromatic aberration as well.
Both flare and ghost images are caused by unwanted reflections or scattering from the various exposed surfaces within the lens and camera body. The glass surfaces of all the lens elements will contribute, as will the glass surfaces of the filter. Typical modern lenses contain up to 15 or more elements, and the addition of one more element (the filter) is not likely to make much difference in most practical circumstances.
I have never seen any convincing evidence that the presence of a good quality filter increases flare to any noticeable extent with ordinary camera lenses.
However, there is a particular circumstance in which the presence of a filter may cause noticeable ghost images. With some lenses, when used at full aperture (or nearly so), light 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 opposite 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 aperture if a filter (any 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).
Both the above images are overexposed and this makes the ghost images more noticeable. Even so, it is only the brightest lights that produce ghost images that are bright enough to be seen (and then only 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 so the sun shines brightly).
Notice that there is considerable flare near the floodlights and this is the same in the two images. The leftmost floodlight produces particularly strong flare which can be seen both as a fuzziness and spreading of the floodlight itself and also as a purplish haze which seems to surround the crane on the extreme left.
Loss of light
I have never seen any convincing evidence that a good quality UV filter causes noticeable loss of light through the lens. Indeed, that would not be expected as the filter is just one additional glass element and most modern lenses already have at least 7 elements and often twice that number or even more.
Loss of resolution
Again, I have never seen any evidence 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 any slight variation from optical flatness (as may occur with a very cheap filter), the effect will be most noticeable with extreme telephoto lenses because of their magnifying effect.
My evaluation of the evidence is that there is no really compelling evidence 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 only 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 confident in cleaning the filter than in cleaning the surface of the lens.
However, I think those photographers who choose not to use filters have a sound case as well!
The effect of a dirty lens (or filter)
In comparing images taken with and without a filter, one thing I have noticed in doing the tests is that even a slightly dusty lens occasionally has a noticeably deleterious effect on the image. This only occurs in extreme lighting conditions such as when the sun is shining brightly and is within the image frame, or very close to it. Under such circumstances, light scattered by dust particles on the front element of the lens or on the filter can significantly increase the stray light falling on the image.
It's generally not worth worrying about a little dust on the lens (or filter). In normal circumstances dust on the front 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 good idea to clean your lens (and filter) first.
|Dirt Hose by poppyjk|
|European bee-eaters by drvanger|
from A Big Year - birds
|Fat Is Beautiful Guinea 2008 DP by MarioSS|
from - Fat is Beautiful - (Woman's Portrait n Black and White+ A Border)
The a9 boasts impressive capability. As more examples of it in practice pour in, Sony's claims hold up. Watch the a9 track and maintain focus on a rapidly approaching basketball.
Last week, more than a million tonnes of Californian coastline slid into the ocean, taking part of Highway 1 with it. Check out the remodeling in photos taken before and after the landslide.
Even after eighteen months of reviewing the latest, greatest, shiniest and must-buy-me-est new gear, DPReview staffer Carey Rose has continued to use older DSLR cameras for his freelance work. But now, that might be changing. Read more
Sony is the world's leading mirrorless camera brand but remains third for ILCs overall, it's said in a presentation to investors. A focus on high value cameras and lenses should boost operating income, it says. Read more
It's nicknamed the 'Cycloptic Mustard Monster,' and is a 3D printed medium format camera. Read more
The new NanGuang LED lights are battery powered and come with accessories including filters and diffusers.
Have you been telling yourself, "Hey, I really need one of those 8K displays?" A video about Dell's new 8K monitor shows you what to expect. Is it really that much better?
Tamara Lackey, a Nikon ambassador USA and pro shooter, discusses embracing self-consciousness as a means of connecting with subjects.
There's a new Spiderman movie coming out and the poster been generating a lot of online chatter. Mostly about how it looks like the creation of a fevered teenager that just discovered Photoshop.
An honest defense of the system's merits, with photos as proof.
Copyright disputes are no fun at all. 'Binded' is a new startup that aims to simplify the process of registering - and enforcing - copyright for photographers. Read more
Not everyone wants to pay a premium for a long zoom camera. Thankfully, there are many reasonably priced cameras available, though they won't offer the same image quality as enthusiast models. In this updated roundup we look at big zoom cameras with more consumer-friendly price tags. Read more
Think Tank Photo has updated two of its popular bag lines with improvements to functionality. Read more
We’ve all seen Bob Jackson’s Pulitzer Prize winning photo, but there's another.
The sample footage looks good.
It will automatically pick the best camera settings depending on shooting conditions. It even promises enhanced functionality for your camera, like exposure and focus stacking. It already supports many cameras from Canon, Fuji, Nikon and Sony. Read more
As if $13,950 wasn’t enough to pay for a special edition lens, the Leica Store in San Francisco is offering a prototype of said lens for $24,995. Read more
Make those old photos disappear without deleting them forever.
Firmware updates enable 10 fps shooting with adapted A-mount lenses, and faster startup times and better compatibility for 20 fps shooting when using native lenses on the a9.
Fujifilm has released firmware updates for its camera models X-T2, X-Pro2, GFX 50s, X-T20, X100F and X-T1 and updates to three of its software products.
A 22 year-old Romanian photographer uses his DJI Phantom 4 drone to capture unique perspectives of the city where he now lives.
What's it like to ride the waves with champion surfer Kelly Slater? This VR video from Teton Gravity Research gives you a taste.
When Nikon released the full-frame D3 in 2007, it changed the professional photography industry. In this week's Throwback Thursday, Barney remembers a legend. Read more
The new stuff should have better red hues, improved sensitivity and finer grain - but don't worry - will still shift blues to green, greens to purple and yellows to pink.
Ricoh has introduced a new rugged compact camera with a 16MP CMOS sensor, 28-140mm lens, 2.7" LCD and built-in LED macro lights. Read more
This compact drone can shoot HD video using a 2-axis stabilized 12MP camera. Read more
The new Prynt Pocket can print a photo directly from their iPhone simply by inserting the phone into the printer, then snapping a photo. Each print will cost about 50 cents. Read more
Updates for Adobe Camera Raw and Lightroom CC bring support for the Sony A9 and Panasonic ZS70/TZ90, along with bug fixes.
The Triggertrap remote camera control system is no longer sold due to the company folding, but now users will be able to build their own. Read more
The Magic Format Converter comes with internal optics that expand the image circle of full-frame DSLR lenses for use on the Fuji medium format camera. Read more