When the Sony A9 came out in 2017 I had been with Sony full frame mirrorless cameras for 3 years already. The benefits of the stacked sensor really intrigued me, but it wasn't until 2021 that I managed to pick up a second hand A9 from ebay. Having owned an A7III for a couple of years prior to this, the big question was; Is the A9 still worth it (4 years later), compared to newer lower and higher end models?...
The Sony A9, Sigma 85mm f/1.4 DG DN ART lens & Angelo Pelle wrist strap
The A9 was initially marketed as the first real mirrorless competition to professional DSLRs. It was smaller, lighter, faster, higher resolution and cheaper than the Canon 1DX mkII and Nikon D5. Funnily enough, this seems even more true of Canon & Nikon's next (and final?) generation DSLRs now that price is an even bigger gap. Sony also began launching big pro lenses in 2017 to entice more professionals to switch. They now have a 400mm f/2.8 and a 600mm f/4. I'm sure the 300mm f/2.8 and 200mm f/2 won't be too far behind. It takes a lot for professionals to be tempted away from their reliable lens systems, but this push from Sony seemed somewhat successful.
The A9 has some really impressive features and focus capabilities, but on the flip side - many pros didn't like the tiny body/grip, lackluster battery life and key feature omissions. The latter would be addressed in the mkII (2 years later), but it was otherwise a rather disappointing upgrade (build, battery, sensor and speed being identical). The new A1 is Sony's answer to Canon's latest mirrorless camera (R5) significantly raising the bar in many areas, but the even more cutting edge high-res version of the stacked sensor comes at a hefty price! Unfortunately Sony still haven't upgraded the rear LCD or overall build, grip and battery life of their pro cameras since the A9. This doesn't look too terrible now, but if the new pro mirrorless offerings from Canon & Nikon become a reality soon then Sony might need to reconsider
Much of the A9's benefits are about speed. Compared to other mirrorless cameras; It starts up quicker, has less shutter lag, a higher max shutter speed, it scans quicker, focuses quicker, tracks quicker, shoots quicker, updates the viewfinder quicker & never blacks out. For DSLR users it also provided: 5 stops of image stabilization (for lenses that don't), far more AF sensors over a much larger area, eye-AF (for humans and animals), a tilting LCD screen and no need for lens calibration.
The mid-range the A7III was a big step up over its predecessor due to borrowing some of the A9's innovations. In practice, if you're using it for speed critical subjects like wildlife, the A9 is light-years ahead.
On the rare occasions when I feel the need to use the maximum 20fps burst it always delivers! At full speed the buffer allows for just over twelve seconds of continuous shooting. This might not sound like a lot, but at 20fps it provides an absolute ton of images to look through! For your sanity I don't recommend holding that button down just because you can, but it's damn nice to know it's there!
It's capability is impressive, but more importantly it gives you the confidence to shoot pretty much anything. Misses are usually your fault, giving you the ability to fine tune your skills, rather than getting frustrated by hitting technical limitations.
12bit vs 14bit
There seems to be some confusion about when the A9 can shoot 14bit. I have heard many Youtube reviewers say that if you use the electronic shutter or compressed RAW files that the camera will be shooting 12bit, but this is not true. You can shoot both silent and compressed while retaining 14bit RAW files, just as long as it's in single shot mode. Any speed of continuous shooting will cause the camera will drop to 12bit. I was initially reluctant to use the burst speeds because of this, but thus far I have not seen any detrimental effect to shooting 12bit when processing.
The A9 came before any of the A7 mkIII series, thus compared to the a7 mkII series there were a lot of improvements that were first seen in the A9 and followed on to every A7 camera after that point. Things like a deeper grip, focus nipple, an improved record button location, dual memory cards and the amazing Z-type battery. Eye-AF and 4k had existed before, but were much improved here, although the latter would lack colour profiles for no good reason.
One thing that would never filter down to the A7 cameras was the left dial. This has two sections (upper and lower) that control focus modes and shooting speeds. It's really nice not having to delve into the menus for these or assign them to custom buttons. It would be useful to have this on all of the A7 series as well, but I get that Sony want some way to have a physical difference on the pro models.
The main feature of the A9 is it's stacked sensor. This provides a two amazing features. Firstly; the sensor scans at a very high speed when using the electronic shutter / silent mode (1/160th). This allows you the confidence to leave the camera in silent shooting mode most of the time without having to worry about rolling shutter. Secondly; The viewfinder has no blackout when it is shooting silently, no matter the burst speed and unlike many other mirrorless cameras this is not because it displays the last frame until it's finished recording. The view is unhindered by shooting. Since this is such a bizarre sensation it's actually nice that the camera has a fake sound and various options for flashing symbols to help tell you that you have actually taken a shot.
Sony have a long head start concerning full frame mirrorless lens development. They now have 60 of their own lenses, many of them are very good and almost justifiably expensive. Perhaps even more impressive is that Sony made their lens mount opensource. This has encouraged many other lens manufacturers to make their new lenses available for the Sony E mount and not others. There are already several very good third party lenses (from Sigma and Tamron) that are available for the Sony A7/A9/A1, but not for Nikon or Canon's mirrorless cameras.
The Sigma lens shown above is one of these. This Sigma DG DN 85mm f/1.4 FE ART lens was used to take the following shot (and the bokeh panoramas, below). This is a nicer option than the Sony GM in my opinion. Having all the same controls, matching or beating the optical quality, firmly beating it on focus speed and noise, while being smaller, lighter and cheaper. The Sigma DG DN 100-400mm FE (which I used to take many of the wildlife photos shown here) is another amazing lens you won't find for Canon or Nikon. Weighing just over 1KG it offers superb image quality, auto focus and great image stabilization for the size, weight and price.
Another of my favourite lenses is the Sigma (I am a much bigger fan of Sigma than I used to be) 135mm f/1.8 ART lens. I would love for this to be available as a mirrorless design, but thus far there isn't one. I use the Canon EF mount version, adapted to FE via the MC-11 adapter. This lens was a pain to focus on the A7II, but here it works better than many of my native Nikon lenses did on the pro DSLRs and that is an incredibly impressive illustration of how far the focusing has come on the A9!
If you're not sure what this is (go here for more info); It's the stitching of multiple shallow depth of field images shot on longer focal length lenses to emulate an impossibly fast wide angle lens. Something akin to large format or beyond.
I started shooting this technique on the Nikon D3 (2009), switching to the Sony A7 (2014) was a big help for shooting this technique, but the A9 has a few nice additions that make this technique an even nicer experience. Firstly - you can shoot silent, so the excessive amount of image you need to shoot doesn't kill your camera, without worrying about rolling shutter. Doing this on the A7III, which scans at less than 1/10th the speed, frequently messed up the geometry of the images, breaking the stitching process. Secondly - you can shoot up to 1/32000th with the electronic shutter (used in the 3rd example below). This is extremely useful when shooting fast lenses in bright conditions and not wanting to blow out the highlights.
So, is the A9 worth it in 2021? For me the answer is an emphatic yes! This was a massive improvement over previous Sony cameras, even the mighty A7III. I have enjoyed previous Sony A7 series cameras before, but even though they offered a lot over DSLRs I've always thought they lacked something too. Perhaps they still do with battery life, although the Sony is better than most others. Compared to other mirrorless cameras the Sony's grip is still a little dissapointing, although I have been very happy with the additional thumb and pinky grips. I guess the main reason why I'm so happy with the A9 is the focusing and silent shooting ability. The burst speed is also nice, but even if it was 10fps for 3 seconds I'd probably be fine with it, so is largely overkill for me.