Just sharing my experience: I went through this last year when I first grabbed the a9 III. Basically, that global shutter is a total beast, but it’s highkey picky about glass if you actually wanna hit 120fps. I tried to save some cash using the Sony FE 200-600mm f/5.6-6.3 G OSS for night soccer, but honestly? The f/6.3 was a disaster under those dim stadium lights. My ISO was through the roof and the AF occasionally hunted cuz of the narrow aperture. Over the years, I've found that building a kit around the Sony FE 70-200mm f/2.8 GM OSS II was the smartest move for my wallet and my back. Here’s what I ended up doing: * I use the 70-200mm II bare for basketball—it’s literally the perfect court lens.
* I pair it with the Sony FE 1.4x Teleconverter SEL14TC for field sports to reach 280mm at f/4.
* I skip the 2x converter cuz the image degradation and light loss just wasnt worth it for me. This setup stays SO light for handheld shooting and those XD linear motors are the only way I've been able to maximize the 120fps burst without any lag. anyway...

> do you think the 70-200mm with a 1.4x teleconverter is a better move than the bigger zooms? Quick reply while I have a sec... Over the years, I've tried many combos, but 100% go for the Sony FE 70-200mm f/2.8 GM OSS II (around $2,798). If ur on a budget, just grab the Sony FE 1.4x Teleconverter for $548. It’s way cheaper than a dedicated field lens and actually keeps that 120fps. Third-party lenses will highkey bottleneck u to 15fps, so basically dont even bother. gl!

Coming back to this... I really have to agree with Cynthia on the sensor risk. I learned that lesson the hard way at a dusty track meet a few months back. Since this body doesnt have that mechanical curtain to hide behind, I was being a bit too reckless during a quick lens swap and ended up with some nasty debris inside. It took ages to get it spotless again, and honestly, it made me way more conservative with how I handle my gear in the field. Now, I am basically a ninja about it. I usually keep a lightweight rain sleeve on at all times just for dust protection, and I have mastered the under-the-shirt swap to keep the internals safe. It is a bit of a DIY hassle, but when you are shooting fast-paced stuff for hours, you really dont want to be worrying about your sensor getting trashed by a random gust of wind. Just something to keep in mind if you are planning on switching between setups while standing on the sidelines.

Quick reply while I have a sec. I've been shooting varsity sports for a decade and unfortunately the Sony FE 200-600mm f/5.6-6.3 G OSS really let me down on the a9 III. I had issues with the AF motors just not quite keeping pace with the 120fps burst during fast transitions, and that f/6.3 is just miserable in those dimly lit high school gyms. Honestly, it's not as good as expected for a camera this fast. My go-to now is actually the Sony FE 300mm f/2.8 GM OSS. It's pricey at $5,998 but it's incredibly light for handheld work and the balance is perfect for hours on the sideline. If that's out of reach, I'd suggest looking at the Sony FE 100-400mm f/4.5-5.6 GM OSS (around $2,498) over the 200-600 any day. The AF is much snappier for tracking fast action. I tried using the 70-200 with the Sony FE 2.0x Teleconverter but the results were kinda soft and disappointing compared to bare glass... the 1.4x is definitely the better move if you need to keep things light.

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For your situation, warning: stay away from that f/6.3 zoom for night soccer. honestly, the light loss is a killer. in my experience, the fast f/2.8 zoom with a 1.4x converter is way better for the 120fps burst. it stays light for handheld use and the AF is sooo much more reliable. i've tried many setups and slower glass just wont cut it when the sun goes down lol. TL;DR: Fast glass + converters beat slow zooms.

> I also tend to shoot handheld for hours at a time, so the weight of the lens is a huge factor for me. One thing everyone forgets to mention is the risk youre taking with the sensor on the a9 III since it doesnt have a mechanical shutter protecting it during lens swaps - basically the sensor is always sitting there exposed to dust and debris on the field. If youre doing outdoor sports, you realy need to be careful about DIY sensor cleaning. Its highkey risky compared to older bodies. Before you commit to any setup, check out the official Sony support site for the ILCE-9M3 compatibility - they have a specific list of which lenses actually support the 120fps AF/AE tracking. Its not just about the glass, but the firmware version too. Im not 100% sure if youve checked yet, but sometimes you gotta do a DIY firmware update on the lens itself to get the full performance of those linear motors. Couple of resources to look at:

• Sony Support Continuous Shooting Compatibility list
• Firmware update downloads for E-mount glass
• Professional sensor cleaning kits vs pro service centers Definately avoid trying to self-service a sensor scratch tho, get a pro if the dust wont budge. Its a beast of a camera but those internal components are sensitive when exposed.