Originally posted by tibbitts For those who find filters affect their images in noticeable ways, is the issue primarily resolution or flare? I have had only one filter ever that I could tell affected resolution, and that was dramatic, while many filters have had an effect on flare, but only that I could see under specific circumstances. However my highest resolution body is only 16mp with an AA filter, so maybe this is becoming more of an issue as sensor resolution has increased.
I've mainly noticed a slight softening when using filters on telephoto lenses. It's only obvious when reviewing images with fine detail at 1:1 or greater reproduction ratios while processing / editing. Additionally, I've had some light reflection issues. I have a whole series of shots with magenta blobs in them, taken indoors at a railway museum that uses strong overhead spot lighting. I'd forgotten to remove the UV filter from my lens, and all but a handful of those shots was affected.
But the biggest issue I've encountered was with UV filters that introduced a strange diagonal lines in the out-of-focus areas. See a couple of my earlier threads here:
Always test your filters! - PentaxForums.com Further testing - UV filter and diagonal lines in bokeh - PentaxForums.com
The take-aways from this are (1) if you're going to use UV (or any other) filters on your lenses, test them first and carefully review your images at 1:1 reproduction to ensure you're happy with the results, and (2) remove them if there's a strong light source in front of the camera (even if it's outside of the visible frame)...