Sooo, I went through this exact same process last year with my RF 24-105mm. It's such a versatile lens but finding filters that dont ruin the image quality is highkey a struggle. I spent way too much time testing different options because I was worried about that 24mm vignetting too... Basically, here is what I learned from my journey: 1. Multi-coating is non-negotiable. I tried a cheap unbranded UV at first and the ghosting in backlit scenes was literally painful. I ended up with the Hoya 77mm NXT Plus UV Filter and it's been super solid for the price.
2. Frame thickness matters SO much at the wide end. I found that anything over 5mm starts showing up in the corners at 24mm. 3. For landscapes, I eventually grabbed the K&F Concept 77mm Nano-X Series Slim CPL. It’s slim enough that I dont see dark corners, and the color shift is minimal compared to the super budget ones. Anyway, that was just my experience! It really depends on how much you want to pixel peep, but these mid-range options worked for me. Peace!

I totally agree that multi-coating is a huge deal - honestly, why risk an expensive L-series lens on a cheap piece of glass, right? Since I'm still kinda new to this, I was super worried about the reliability of different brands too, but here are a couple of things I've found that really help with peace of mind: * Try the B+W 77mm Master 010 UV-Haze MRC Nano for protection. It uses a brass frame which is way more reliable because it doesn't bind or get stuck as easily as aluminum ones - especially if you're traveling through different temperatures, you know?
* For the CPL, maybe look into the Breakthrough Photography 77mm X4 CPL. They're famous for being super slim to avoid that 24mm vignetting and the traction on the ring is great so it won't slip out of your hands. But yeah, I'm always paranoid about things getting stuck - does anyone else use a lens wrench or is that overkill for travel?

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TL;DR: My deep dive into spec sheets suggests that the high-end Japanese manufacturers often have the best tech-to-price ratio, so basically look at those brands if you want quality without the boutique markup. Just catching up on this thread! I'm still pretty new to the actual photography side of things, but I'm a total nerd for technical data, so I spent hours looking at light transmission charts and refractive index ratings before buying anything for my RF lens. Honestly, it's wild how much the market varies between the German and Japanese brands. I was comparing the lab tests for Marumi versus some of the more expensive brands mentioned here, and the data is pretty similar. I also looked into Kenko, which is basically a massive player in the Japanese market that people sometimes overlook elsewhere. From my research, the coating technology on the premium Japanese lines is super impressive for preventing that ghosting you're worried about. Tbh, you can't go wrong with anything from Marumi or the higher-end Japanese lines. They've been doing this forever and the specs really hold up, you know?