What is the best 85mm portrait lens for Sony a7 IV?

Question

so i finally pulled the trigger on the a7 iv after saving up for like a year and now im staring at my bank account and these lens listings feeling totally overwhelmed. i have a huge family reunion and portrait session coming up in about three weeks in a local park near seattle and i really want that creamy blurred background look for the individual shots but i cant decide which 85mm is actually going to work best with the autofocus on this body.

im basically torn between three options right now:

the sigma 85mm f/1.4 dg dn art

the sony 85mm f/1.8

maybe a used sony 85mm f/1.4 gm if i can find a deal

the sigma seems like the sweet spot for quality but im honestly terrified about the weight and if the autofocus is gonna hunt while im trying to catch the kids running around because they never sit still for more than two seconds. then i look at the sony 1.8 and it is so cheap and light which sounds amazing for a long day of shooting but am i gonna regret not having that extra bit of light and the 'pro' feel of the 1.4? i have about 1200 dollars to spend max and i really dont want to have to buy a lens and then realize it was the wrong move and have to deal with returns right before the shoot. the gm is the dream i guess but even used its pushing my budget and i keep hearing it is loud and slow compared to the newer stuff? my hands are literally shaking a bit typing this because i just want to make the right choice and not blow my savings on something that isnt going to give me those sharp eyes and blurry backgrounds i need. does the sigma track well enough on the a7 iv for moving people or should i just play it safe with the native sony glass even if its the cheaper 1.8 version...

Bruceslile · Accepted Answer

ngl i went through this exact same panic when i got my a7 iv. i spent a whole weekend at a local park testing different glass because i couldnt decide if the extra weight was worth the f/1.4 look for my portfolio. honestly for kids running around in seattle weather the Sony FE 85mm f/1.8 is a sleeper hit because the dual linear motors are incredibly snappy and it basically never misses eye-af even when they are sprinting.

Sigma 85mm f/1.4 DG DN Art: this is the sharpness king and weighs about 630g so its not a total brick. the af is definitely fast enough for portraits but might hunt slightly more than native glass in low light.

Sony FE 85mm f/1.4 GM: id skip this for active kids. it uses an older ssm motor that feels sluggish and loud compared to the newer options. the sigma gives that creamy look you want and fits your budget perfectly while being way more modern than the old gm. if you prioritize hit rate for the kids tho the 1.8 is hard to beat.

TebeAlish · Answer

I've spent years testing these setups and the technical specs tell the story. The Sony FE 85mm f/1.4 GM is a beautiful lens but it uses an older motor system that feels clunky on the a7 IV during high-speed tracking. Focus performance on that one is hit or miss compared to the newer glass. If you're worried about kids, the Sony FE 85mm f/1.8 is actually the best bet for pure AF speed... it has less glass to move so it snaps to the eye instantly. I did a weekend shoot with the Sigma 85mm f/1.4 DG DN Art recently and the stepper motor is incredibly precise. It weighs around 630g which is totally manageable compared to the old 1kg monsters. If you want that f/1.4 look without the GM price tag or the slow focus, the Sigma is the technical sweet spot. Dont overthink the weight, the balance on the a7 IV is actually pretty decent with that Sigma.

ZitalaSmoth · Answer

Coming back to this, is the park shaded? Ive seen shoots ruined by harsh sun and cheap glass with terrible purple fringing! Its a total nightmare!How many kids?Printing big?