What is the absolute best prime lens I can get for street photography on my Sony a7C II that actually stays small but doesn't suck in low light? Honestly I'm so fed up with this 28-60mm kit lens that came with the body, I thought it would be fine for a compact setup but it's driving me crazy. I spent all last weekend wandering around downtown Chicago trying to get some moody evening shots near the Loop and everything just came out like a grainy mess because the aperture is so slow. It's frustrating because I bought this specific camera for the small form factor but now I feel like I'm stuck between a tiny lens that performs poorly or a huge lens that ruins the whole point of having a compact body.

I really need something fast, at least f/2 or better, because I do a lot of shooting at night or in dimly lit alleys. I've been looking at the Sony 35mm f/1.8 but I've heard mixed things about the build quality and some people say the 40mm f/2.5 G is the way to go for the a7C series but then I'm losing light again which is exactly what I'm trying to avoid right now... it's like a never ending circle of trade-offs.

Here is what I am looking for:

• Needs to be compact (no massive lenses that weigh a ton)
• Fast aperture for night street stuff
• Quick autofocus because I hate missing shots of people moving
• Budget is around $850 give or take

I'm heading to Tokyo next month and I really want to have this figured out before I go so I'm not lugging around gear that makes me miserable the whole time. Should I just bite the bullet on the 35mm f/1.4 GM and deal with the size or is there some middle ground I'm missing? I've even looked at some Sigma stuff but I'm worried about the weight distribution on such a small body. What are you guys actually using that doesn't feel like a brick?