This instructables show how to build a mirrorless interchangeable-lens camera for makers.

Supplies

LilyGo T-Display S3 Pro With GC0308 Camera option (we only need the camera PCB)
OV2640/OV3660/OV5640 Camera with M12 mount and 24p DVP interface (a little bit long FPC is preferred)
M12 varifocal zoom lens
Four 12 mm M2 flat head screws
Tiny camera tripod

Step 1: What Is Mirrorless Camera?

The full name of mirrorless camera is mirrorless interchangeable-lens camera.

Previously, interchangeable-lens camera is DSLR (Digital Single-Lens Reflex) camera. Start from digital camera, the optical viewfinder can be replaced by a digital viewfinder or live view screen. Then the whole optical design are simplified and the mirror of DSLR also be eliminated, so the new design interchangeable-lens camera is called mirrorless camera.

Ref.:

https://en.wikipedia.org/wiki/Digital_single-lens_reflex_camera

https://en.wikipedia.org/wiki/Mirrorless_camera

Step 2: Camera for Makers

A interchangeable-lens camera is a good way to study how does optical physics work. Especially using full manual focus lens.

However, the price tag of a mirrorless camera is not suitable as a study material. Fortunately, as a maker, we can make one for our studies ;)

Step 3: M12 Lens Mount

M12 lens mount is the smallest lens mount system that have varifocal zoom lens in the market. At the same time, maker dev device commonly used image sensors (OV2640/OV3660/OV5640) have M12 mount version in the market. Follow this coincidence, I chosen M12 lens mount for this mirrorless camera project.

Step 4: Dev Device

Since we selected M12 lens mount, we need select a similar size dev device as a camera body. The dev device should have built-in camera support and a color display for live view. LilyGo T-Display S3 Pro capable to do it.

Step 5: 3D Printing

T-Display S3 Pro already has a very good case body. But we still need some modification to have a M12 lens mount.

Please download and 3D print the 3D models at thingiverse:

https://www.thingiverse.com/thing:6464712

Step 6: Assembly

Follow the video steps for the assembly and something to note:

The leather sticker decoration is optional, you also can decorate with different materials
The camera sensor can be installed in 2 different angles depends on what sensor version you bought
The screws fixing camera sensor are optional, depends on is it provided when you buy the sensor
Highly recommend use tripod for the stabilities of manual focus, any tiny camera tripod should be ok

Step 7: Sample Camera Program

Please follow LilyGo Github page to install required software:

https://github.com/Xinyuan-LilyGO/T-Display-S3-Pro

And then here are the draft sample camera program for testing:

https://github.com/moononournation/T-Display-S3-Pro/tree/main/digital-camera

Step 8: Sample Photo

The sample program will take photo if pressed the button (GPIO 12). The photo will store to SD in the folder "/DCIM/100ESPDC".

The above are some sample photos for your reference.

Step 9: A Long Way to Go

Since this camera is designed for makers, it will have infinity possibilities. Every maker can modify their own version and all versions probably will be open sourced, so it can evolute quickly.

One of the scope require substantial enhancement is the software:

Use NTP & RTC to record photo taken time
Store photo thumbnail
Replay function
Manual focus aids features, e.g. enlarge center part to help more precise focus
With the specific sensor, also can enable auto focus
OSD for displaying camera status, e.g. battery level, memory status, storage remain, date time, sensor configurations ...

And since maker can plug more modules to enhance this camera, so it also can:

Use GPS module to store location data to photo file
Use 9-axis module to store photo taken angles and motions
Use weather sensors to store temperature, humidity, pressure and even air quality while photo taking...

Since it is WiFi connectable, it also can: