A recent social media campaign by Urth, promoting their new magnetic filters, claims to increase sharpness (emphasis my own)
Our professional Ultraviolet Filter Plus+ cuts UV light to make your images clearer and sharper and protects your lens from scratches, oil, dirt and water.
I was always told UV filters can reduce sharpness, and are really only any good as a temporary form of protection.
I asked Google Bard the question "In photography, can a UV filter increase the sharpness of an image?". It replied with
No, a UV filter cannot increase the sharpness of an image. In fact, it can actually decrease sharpness slightly. This is because a UV filter adds an extra layer of glass in front of the lens, which can cause diffraction and reduce contrast.
UV filters are designed to protect lenses from scratches, dust, and other elements. They can also be used to reduce the amount of UV light that reaches the sensor, which can be helpful in high-altitude or other environments where there is a lot of UV radiation.
However, if you are concerned about image sharpness, it is best to avoid using a UV filter. If you need to protect your lens from the elements, you can use a lens hood or a camera bag with a padded compartment for your lens.
Is there evidence to prove that a filter can increase sharpness? Or is this disingenuous marketing/creative writing?