The Sony a7S series of cameras is strange. They're described as stills cameras; however, most customers seem to use them for their video features. At best, they're an odd compromise that doesn't fit anywhere properly. For this reason, I'd like to discuss why Sony should get rid of this line completely or at the least, revamp the series.
Low-Resolution Sensors Offer No Advantage in Low Light
The Sony a7S III is the latest in the a7S series of cameras. One of the assumed benefits of this camera and its predecessors is that it offers better low-light performance. This is quite easy to disprove. If you have a lower-resolution sensor, then each pixel is going to be relatively larger. Larger pixels have the potential to be more efficient when it comes to gathering light. And this is thought to help improve high-ISO performance. In practice, this is only somewhat true at best.
For example, if you take a picture with the 12-megapixel full-frame Sony a7S III camera at ISO 12,800, you'll notice some noise in the image. Compare that to an image taken on the new 33-megapixel full-frame Sony a7 IV camera, and the latter will demonstrate slightly more noise in the image. However, if you take the same image from the a7 IV and scale it down to 12 megapixels you'll end up with near-identical noise performance between both cameras.
What's more is that the Sony a7 IV image will appear sharper and have more detail than the image taken with the Sony a7S III. If you're interested in testing this theory, you can hop over to the Studio Shot comparison from DPReview, download high-ISO raw files from the two Sony cameras, scale down the resolution to match, and check for yourself.
Otherwise, here is a quick demonstration of this fact with two different cameras.
The cameras I have used are the Canon 5DS R and the Canon 5D Mark IV. Above, you'll see the difference in noise performance when both files are compared at their respective resolutions. However, as soon as you scale down the resolution from the 5DS R image to match the Mark IV, the difference in noise performance becomes negligible.
As soon as you match the resolution in both cameras, the difference in high ISO performance becomes practically identical. This is more pronounced when you compare images between the Sony a7S III and the Sony a7 IV. Once again, you can find sample raw files to perform this comparison yourself using the DPReview link above.
What this proves is that lower-resolution sensors offer virtually no advantage when it comes to high-ISO or low-light performance. All you have with the Sony a7S III is a low-resolution camera without any real upside. With a higher-resolution camera such as the Sony a7 IV, you have the best of both worlds. The resolution is there when you need, and if you want comparable low-light performance, you can always scale down the resolution for cleaner files.
12 Megapixels Is Not Enough
I always find it a little cringeworthy when someone tries to discuss why 12 megapixels is enough. Common arguments include statements about how large you can print with 12 megapixels or how little resolution is required for printing in a magazine, or even points about how much resolution is required for a 4K display.
By that logic, two megapixels should be enough because you can print as large as a billboard with that amount of resolution. This is hyperbole; however, the point is that using a camera with the lowest feasible amount of resolution is a bad idea. No professional worth their salt would work with the bare minimum that's required in any other scenario. Therefore, this must apply when it comes to resolution too.
An apt comparison would be the two card slot issue I assume there are very few professionals that are comfortable shooting an entire paid shoot with just a single storage card. Realistically, you only need one card, so what is the problem, right?
The answer is redundancy and security. If you're a professional and you're using the bare minimum required for a job, you're leaving yourself open to a whole heap of potential problems.
This translates over to resolution too and more resolution (over 12-megapixels) is better because it offers a greater deal of flexibility. For many photographers, somewhere between 20 and 30 megapixels is the sweet spot of what's required. You have enough resolution for most applications and then some should anything occur.
Of course, I understand that to many, the Sony a7S series of cameras are not precisely geared towards photographers. Instead, it's widely understood that these cameras are designed primarily for their video features, hence the low resolution. Well, let's explore that point in detail below.
A Weird Compromise
As discussed above, the low resolution of the Sony a7S III makes it a poor choice for photographers. Despite this, the camera body is designed primarily for photographers and not videographers.
Cine cameras are built differently, and the Sony FX3 is a perfect example of this. The Sony FX3 is essentially a cine version of the Sony a7S III. It has virtually identical specifications, and the only real difference is that it has a different body and different button layout. With this in mind, what is the point of the Sony a7S III?
If you're interested in the video features, then the FX3 is the better option. On the other hand, if you're a photographer, then the Sony a7S III is a poor choice considering the many other higher-resolution options available from Sony. The fact is, the Sony a7S III doesn't quite know what it is. It compromises its stills features to try to offer better video features, even though a better cine camera exists with the FX3.
The Biggest Problem
The biggest problem with the Sony a7S III is its impact on the other Alpha series cameras from Sony. The Sony a7 IV was recently released, and this camera could have been the perfect all-rounder system, but it just misses the mark.
For photographers, it's a brilliant option. Unfortunately, it has a disappointing limitation for videographers.
When you're shooting 4K at 60p, the sensor is cropped to what is effectively an APS-C sensor. This feels like an intentional limitation to prevent customers from losing interest in the a7S series of cameras. If the Sony a7 IV did not crop the sensor when shooting 4K at 60p, it's unlikely anyone would pick the a7S III.
This is quite telling about what customers want, and Sony understands this, hence the limitation. Many customers seem to want a camera with a resolution between 20 and 30 megapixels and great video features without crop-factor limitations. This isn't unreasonable by any means because Sony can do it, and manufacturers such as Canon have already done it with the EOS R6.
The fact that Sony has the FX3 available along with the a7 series of cameras means that the a7S series of cameras no longer needs to exist. All it's doing is ruining the potential for the Sony a7 series of cameras and muddying the lineup.
Ultimately, the Sony a7S III just doesn't make any sense and feels confused. It's trying to be a cine camera without being a cine camera while simultaneously trying to act as though it's a stills camera. Worst of all, it's preventing the Sony a7 IV from being the proper all-around camera system that it could be.