To Filter or Not to Filter - That is the question...


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theveed

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Apr 20, 2007
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One common advice we hear from photographers is to immediately purchase a skylight or UV filter to protect our lenses. The premise is simple, a clear filter is a cheaper replacement than a damaged front lens element. Most UV filters are bought mainly for protective purposes only these days as UV doesn’t seem to affect digital images anyway.

There are, however, those who will insist that adding a piece of glass in front of a precision-engineered lens will alter the light rays no matter how good the filter is. In addition, quite a number of photographers will also note that filters will induce flare because the lens’ front element is designed to reflect a certain wavelength of light and the filter will actually bounce it back to the lens, and so on.

My philosophy with UV filters is simple, if the glass is large enough and protrudes enough, I’ll use a filter. I’m a rough user and unless it’s a macro lens where the element is deeply recessed, or a cheap lens, or a lens that I’ll never use without a deep lens hood (like telephotos), I prefer to use a filter due to my careless nature.

So today, I tried a simple test on a Canon EF 24-105 f/4L IS USM lens shooting still subjects with a relatively large light-source close to the lens using different apertures with both filter-on, and filter-off. The filter used is an entry level Hoya Standard UV filter.


I’ll let you draw your own conclusion based on the gallery below. You can see the EXIF by clicking on the images. They are sorted by Filter On, then Filter Off with similar exposures.


See gallery here... The gallery won't embed in the forum, sorry

My conclusion, at least for this lens/filter combination, is that the differences can be seen, especially when scrutinized at 100%, but hardly visible enough to say that the difference is pronounced. This could simply be a lens issue, though. I’m pretty sure that different lenses will behave differently, as well as different filters may produce different results as well.

In this case, the image quality differences are minimal, if not negligible. Some images at wide-angle have a little sharpness loss with the filter on, but flare differences are minimal.

A filter may protect the front element from day-to-day scuffs and smudges, it’ll also save the front element from microscopic rub marks from brushes and lens cloths, but in some cases, a filter may cause more damage compared to a more direct impact to the lens. Whether a filter is worth it or not, it’s up to you to decide.
 

night86mare

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Aug 25, 2006
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#2
i use my uv filter like a lenscap.. anyone who's seen me handling it would know what i mean.. :D

anyways, personally i keep it on most of the time unless it gets too dirty, then i just dump it somewhere in my pockets and hope it doesn't fall out. at night definitely will have to take out though!
 

bartleby

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Jun 17, 2008
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#3
Nice test there, theveed. You can really see the difference.

OT:
Are you theveed from tsikot.com?
 

Jul 26, 2002
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Woodlands
#5
Like you said, the difference is hardly noticable and it simply gives me a peace of mind more than anything else.
 

waileong

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#6
Thank you for your effort but people have conducted such tests before. The answer is easy to figure out-- a filter cannot improve the quality of an image, unless it's used for the right purpose. In other words, if there's no UV light to filter out, the effect of a UV filter can only be to degrade the image.

Of course, whether you can see the degradation depends.

What is clear is that there will always be two camps-- the one who believe in protecting their lenses with filters, and those who use filters only when for a legitimate effect. And the twain shall never agree.
 

Zicheos

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Jun 22, 2008
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#7
Thank you for your effort but people have conducted such tests before. The answer is easy to figure out-- a filter cannot improve the quality of an image, unless it's used for the right purpose. In other words, if there's no UV light to filter out, the effect of a UV filter can only be to degrade the image.

Of course, whether you can see the degradation depends.

What is clear is that there will always be two camps-- the one who believe in protecting their lenses with filters, and those who use filters only when for a legitimate effect. And the twain shall never agree.
If that's the case wouldn't it be more advisable to use a MC filter in situations where a UV filter will degrade the pictures? Having lurked in this place for some time I noticed no one seems to pay attention to MC filters.
 

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