I use clears or UVs on all my pricey glass, and on my pricey "video" cameras with attached lenses. Mainly because I'll pick up a camera and go to a party or club occasionally, or take a shot around the house, sometimes test a new light or something.
For run & gun event type of gigs, the filters stay on. I really rarely see any difference, and it's mainly in how flares look. and those kind of gigs, gear gets bumped around a lot more than usual.
For something really pretty/cinematic, more planned, and particularly indoors, I tend to take them off.
Michael which brand you use for UVs? I opened this topic because i bought recently 2 expensive lenses (Sigma 18-35mm 1.8 and 50mm 1.4) and i was thinking about buying UVs filters for those lenses.
If you barely see any difference, i assume you use a top brand like Hoya?
I generally do keep a B&W Sky 1A uv filter on my fixed lens Canon and my 12-120 Angie on the D16. It does help color purity shooting outdoor daylight scenes and I do like the protection. Sometimes take them off for interiors.
To the OP, if you feel you need one on your lenses then by all means.
In my case, I'm careful with my gear, stuck in my ways, and a wee bit frugal. If I were to add a quality UV filter to all my lenses it would cost over $3K. rogar-Dum(DBG):
I routinely use Hoya Pro HD Protective (UV) filters on my Zeiss ZF.2s for event work and feel a bit uneasy if I'm not using one on my lens, especially in situations where the elements (wind/rain) or people (especially kids) could potentially be unkind to the lens. For narrative, in controlled situations and with crew I trust, I run without filters.
I don't see any major critical difference because the filters I use are of such good quality. That's not to say there wouldn't be a very minor difference if you seriously pixel-peeped it. You are buying top quality glass and covering it with glass of (arguably) less quality and by so doing are adding another layer where dust etc can settle. But I think the trade-off is worth it because the extra protection you have for your expensive lens is very re-assuring and once you clean the lens before screwing on the filter and then keep the filter clean, you should be fine.
A real life example - I remember shooting a documentary which featured kids at an art camp and my camera was right amongst the kids as they worked with paints and art materials. The amount of times the children came up to the camera and touched the lens with a paint covered finger was really surprising. Lets just say I was so happy I had my lenses covered!
However, I don't use filters if I'm doing narrative work in controlled situations where I need the absolute best image possible.