Late to the party but ive spent a lot of time with the S series since it launched. One technical thing you should know is that Panasonic, Sigma, and Leica formed the L-Mount Alliance. This means any Sigma lens labeled DG DN with an L-mount fits your S5 perfectly with full autofocus. No adapters needed, it just works. In my experience, if you want that creamy background on a budget, look for a used Sigma 65mm f2 DG DN Contemporary L-Mount. I've used it for many portrait sessions and while f2 sounds slower than f1.8, the glass is so sharp that the subject really pops. Honestly, 65mm is a hidden gem for weddings because it gives you more reach than a 50mm without being as restrictive as an 85mm. It is a fantastic alternative to the Lumix glass if you want something with a bit more character. Worth checking used listings tho.

I felt the same way when I got my S5. Buying the Panasonic LUMIX S 85mm f1.8 L-Mount made me very satisfied with the results. I looked at the Panasonic LUMIX S 50mm f1.8 L-Mount too, but the 85mm creates way more blur for portraits... its just safer sticking with native glass. No adapters needed. TL;DR: Stick with the Panasonic 85mm f1.8 for the best reliability and bokeh.

Coming back to this... I went down a rabbit hole trying to save cash by picking up a used manual lens with a basic adapter for my setup, thinking I was being smart. Honestly, it was kinda a massive disappointment. On paper, the f/1.4 specs sounded like they would give me that creamy look I wanted, but the reality was a technical mess. I spent an entire graduation shoot struggling because the contrast was so low it felt like there was a permanent fog over the sensor. A few things that specifically ruined the experience:

• The micro-contrast was almost non-existent at wide apertures.
• Chromatic aberration was peaking at several pixels wide on high-contrast edges.
• The mechanical tolerances of the cheap adapter caused a slight tilt, making one side of the frame blurrier than the other. I ended up with hundreds of shots where the bokeh looked nervous and busy rather than smooth. It taught me that while cheap glass is tempting, those technical flaws actually matter when you are doing portraits for someone else. I thought I could fix it in post, but you cant really recover details that the glass never captured in the first place. tbh I basically threw away my budget on something that sits in a drawer now because the quality just wasnt as good as I expected. If you are worried about wasting money, just know that cheap often comes with a hidden tax of missed shots and frustration... it sucks when you realize it too late.

Building on the earlier suggestion about the L-mount alliance, it really is a massive relief that you arent just limited to one brand. For a high-stakes event like a wedding, lens reliability is basically everything because you cant afford for the autofocus to hunt or fail while the couple is moving. Honestly, since you're worried about wasting your money, it would help to clarify a couple of things before you buy anything. Are you planning to shoot mostly outdoors where you have plenty of space to back up, or will you be in a tighter indoor space for the ceremony and reception? Also, is keeping the total weight of the setup down a priority for you, or are you fine with a heavier lens if it feels more durable? Knowing those details would make it much easier to narrow down the best choice for your S5.