tgreenhaw wrote:
I always buy a protective filter when I get a new lens. I just bought an RF 16mm f2.8 lens (an incredible lens especially for $300 new).
Whenever I buy slim wide-angle filters, the lens cap doesn't like to stay on.
Does anybody have a recommendation for a 43mm filter for an ultra-wide-angle lens?
Unfortunately, this question, operating to protective filters, usually opens up a can of worms and as you can see the "shouting and counter- shouting has l already started.
The anti-filter came to insist that protective filters will introduce flare and negatively affect sharpness. The pro-filter folks remind us of the possibility of serious lens damage due to various impacts, dust, dirt, great fingermarks, etc.
Technically speaking, anything you place in front of you, even the finest optical glass coated filter can possibly cause the aforementioned issues. A poorly crafted filter will certainly do so. I high-quality filter such as the kind made by B+W, Zeiss, and other reputable and time-honoured manufacturers will usually NOT cause any perceptible loss of image quality.
As for wide-angle lenses, B+W has a very comprehensive stock of THIN filters for wide-range lens applications. Also, note that with ultra-wide-angle lenses LENS SHADE usage can be problematic. The shade would have to be very large and shallow to preclude vignetting, the same problem caused by a filter in a thicker rim or made of thicker glass.
So, here is my personal experience. I do quite a bit of industrial photography on construction sites and other hazardous environments. I am dealing with airborne particles, metal filings, sparks for welding, sawdust, etc. I will use the protective filter in those situations. Over the years, 5 filters needed to be replaced because of damage that would have seriously harmed the front element of my lenses. I have made extremely large prints for trade-show booth displays with no loss of quality due to filter usage. You have used the filter on your other lenses, so I assume you are satisfied withte the quality.
A serious head-on impact or dropping a lens on a hard surface will cause serious damage regardless of filter protection. If the filter is shattered, the shards of glass will, in turn, damage the lens. A lens shade may prevent scratch of the lens by heavy brush or sharp twigs in the woods, etc., but again would not abate a head-on impact.
Here is a link to a very comprehensive website. It explains the thin-filter usage and has a handy "vignetting" avoidance tool that will hel you determthe correct filter for your focal length and filter mount diameter.
https://www.the-digital-picture.com/Reviews/UV-and-Clear-Lens-Protection-Filters.aspxI hope this helps.