Sony a7S III vs Sony a9

This is a full comparison between the cameras Sony a7S III and Sony a9. We compare them by looking at the categories you see below.

Sony a7S III

Sony a9

Manufacturing

These cameras are both manufactured by Sony.

Sony a7S III were released 2020 and Sony a9 was released 2017. That is a 3 years difference. In tech, this period can be of interest since technology is always improving, etc.

Camera	Released
Sony a7S III	2020
Sony a9	2017

Type of camera

Both these cameras are Mirrorless cameras. No difference there.

Sensors / crop factor

Both these cameras have the same sorts of sensor (called "Sony Full Frame") which means that if you compare these cameras side by side the lenses will also have the same experienced focal length. Since both cameras have a Full frame sensor there will be no crop factor.

Camera	Focal length, 50mm f/1.8 **
Sony a7S III	50 mm Full-frame sensor No crop factor/focal length multiplier
Sony a9	50 mm Full-frame sensor No crop factor/focal length multiplier

** Experienced focal length when using a lens such as a common "50mm f/1.8"

Learn more about crop factor and focal length multiplier here:
Camera selection can affect the focal length (Sony)

Resolution

Sony a7S III has a 12 MP (Megapixels) resolution while Sony a9 has 24 MP. If we break down this in more detail this is the data behind the numbers:

Camera	Megapixels
Sony a7S III	12 MP 12007680 pixels 4240 x 2832
Sony a9	24 MP 24000000 pixels 6000 x 4000

Sony a9 has a 100 % larger resolution than Sony a7S III. This could give you more details in the picture but also a possibility to crop more in the pictures, afterward while editing the pictures, if needed that is.

ISO range

Sony a7S III has a larger ISO-range than Sony a9. Sony a7S III has an ISO range that stretches from 80 to 102400 while Sony a9 has 100 to 51200.

Camera	ISO Range
Sony a7S III	80-102400
Sony a9	100-51200

Autofocus and lens compatibility

Both of these cameras have a built-in autofocus motor. Some lenses, that support autofocus, do not have an autofocus motor of their own but this won't cause any problems with these two cameras.

Here is a complete overview of which lenses work with each camera:
Lens compatibility chart for Sony a7S III
Lens compatibility chart for Sony a9

Pictures per second

Depending on what you are shooting the FPS, or frames/pictures per second, can definitely be of interest. Sony a7S III can shoot up to 10 pictures per seconds and Sony a9 can shoot up to 20 pictures per seconds.

Camera	FPS (Frames per second)
Sony a7S III	10
Sony a9	20

Ability to record movies

It is becoming more and more popular to record movies with digital cameras.

In this case, both Sony a7S III and Sony a9 can shoot movies.

Weight

The weight of the camera can be an extremely important factor, especially if the camera is about to be used, or carried around, for several hours at a time.

Sony a7S III weighs 699 gr (equal to 1.54 lb) which is 4% heavier than Sony a9 and its 673 gr (or 1.48 lb).

Camera	Weight
Sony a7S III	699 gr 1.54 lb
Sony a9	673 gr 1.48 lb