I see where you guys are coming from with the reach thing, but I have to respectfully disagree about needing to stick to those traditional focal lengths or the super expensive native glass for the best street experience. Tbh I spent months looking at the market trends and realized the big name brands are charging such a massive premium for those standard 35mm and 50mm lenses, while the third-party market is honestly killing it with more compact options... I actually sold off my heavy native setup a few months back because I was tired of carrying around something that looked like a professional cinema rig just to take photos of people at a cafe lol. I ended up getting this tiny third-party lens from a brand people usually overlook, and it totally changed how I shoot.

• The market data shows these third-party lenses are catching up so fast in terms of autofocus speed that the native advantage is barely there for street anymore.
• I found that my hit rate actually went up with a cheaper, smaller lens because people dont notice me as much... it feels way less intrusive than those giant high-end things.
• Basically, the cost-to-performance ratio on the non-native stuff makes it way easier to experiment with different focal lengths until you find your vibe without breaking the bank. It really comes down to the market being so saturated with good glass now that the ideal focal length is probably whatever you can afford to carry all day without your neck hurting.

The optimal focal length for your Sony a7 or a9 depends on your photographic style and desired perspective. A 40mm lens offers a natural field of view, balancing scene context and subject isolation. Wider lenses (e.g., 24mm) emphasize environment, while longer lenses (e.g., 50mm) enhance subject separation. Ultimately, the "ideal" focal length aligns with your storytelling approach and aesthetic preferences.

Honestly, I think the "ideal" focal length is really about what gives you the most reliable hit rate when things are moving fast. I've been shooting these bodies for years, and while wider is fun, it can be pretty risky if you aren't comfortable getting right in someone's face... which isn't always the safest move depending on where you're shooting. IIRC, a lot of the older street pros swear by having that extra bit of reach just for the peace of mind. Not sure if it's the "purest" way to do it, but using something slightly longer—like in that 40mm to 55mm range—tends to be more reliable for nailing focus without the distortion you get when you're forced to get too close. Plus, the weather sealing on those mid-range primes is usually top-tier. I’ve had some close calls in the rain where I was glad I wasn't swapping lenses or struggling with a focus motor that couldn't keep up. Basically comes down to what keeps your kit safe and your shots consistent. If you can't rely on the glass to perform in a split second, the focal length doesn't even matter.

FE 35mm f/1.4 GM.