Photography

Ahh yes, you will get flare at an almost 90 degree angle to the sun if you have a filter on because it's further forward than the lens itself.

I shoot a few portraits and probably 75% of them are backlit so there's potential for flair to get on my lenses a lot of the time.

So I have three tiers of lens shading to keep sun off my filter. The first is a lens hood. If, due to the angle, the lens hood doesn't stop sunlight or other bright light striking the filter I take off my cap or hat (which I always wear on a shoot for this single purpose) and hold it at the end of the lens would to shade the lens.

Then, if it's still not enough shade I have an assistant or a bystander hold a black card which I have on a stick and ask them to shade the lens with that. Regulars have become very adept at wielding the card on a stick! Then sometimes when I'm going for a strong rim light I will shoot right into the sun and in that situation I remove the filters.

I find it's imperative to take the filters off when I'm shooting at night because any bright light will reflect off the inside of the filter causing bright spots in undesirable places. So that's pretty well any nighttime light source.

If I damage a lens, for me that wouldn't be disaster either. But it would be a financial inconvenience. Then there's also downtime for the time it takes to replace or repair the lens. And on top of that there's the boss (my wife) to take into account!