Based on my research, I think you will struggle to find an easy-to-understand, definitive source for this information. What I have found is that there are three answers to the question of "What is the sensor size of the camera on this drone?" The values you may find on the web will fall under on of these three categories:
- Nominal: This is a nominal sensor size based on the commonly used sensor size terminology such as 1/1.3. If a sensor size is mentioned in marketing material, the nominal size is usually given.
- Actual: This is the actual size of the sensor and may be slightly larger (or smaller) than the nominal size. If you are given the area of the sensor and know the aspect ratio, the actual dimensions can be calculated.
- Active: This is the size of the active area of the sensor which will be less than the actual size of the sensor. This value can only be obtained my measurement.
For example, for the
Mavic 2 Pro, you will find the following sensor size values:
- 13.2x8.8 (nominal)
- 13.19x8.79 (actual)
- 12.825x8.55 (active)
Sources for each of these values include:
A graphical view of the various sensor sizes in DJI camera drones, along with photo and video specs available in different models.
www.djzphoto.com
docs.google.com
Contribute to Theta-Limited/DroneModels development by creating an account on GitHub.
github.com
@Eko Would definitely second what
@DJ Wes says, we've encountered similar difficulty in finding these parameters for use in our
OpenAthena software.
The supposed size of the sensor in spec materials, e.g. 1/3", which Wes calls 'Nominal' is known as
Optical Format; it's just a marketing gimmick owing back from the days of when sensors were based on vacuum tubes which took up their own space. It has little relevance to the actual physical size of the sensor, though it usually gives you a decent estimate once converted. We've found this list to be the most accurate if all you have is the Optical Format size (as DJI posts on the spec page for each of their drones):
There is a lot of misunderstanding about digital camera sensor sizes. Learn how big they really are.
www.digicamdb.com
This article describes the more exact math for converting from Optical to physical size (though again, sometimes the two can be entirely unrelated):
Wondering about digital camera (CMOS) sensor sizes? This article provides information about camera sensor format sizes, general tradeoffs, and lens equivalency.
commonlands.com
What you're really looking for is more likely the Actual or Active dimensions of the sensor. For non-DJI drones, these can often be obtained from the technical spec sheet of the CMOS sensor itself. These documents can be found online, they usually provide pixel pitch (size) in micrometers (μm). Multiply this by the number of pixels height or width and divide by 1000 to convert to millimeters (mm) and this gives you a pretty accurate value for width or height. If the spec sheet specifies Actual vs Effective/Active number of pixels, usually you'd want to use Effective.
Finally, if all else fails you can calibrate a camera manually using a few dozen images taken by it with a script such as ours here:
Python script for manual camera calibration using OpenCV with images of a B/W Chessboard pattern - Theta-Limited/camera-calibration
github.com
It does require you to have a calibration pattern printed on a poster, our company's standing offer is we will generally ship one to whomever for their own drone model if they are willing to
contribute the calibration values they obtain:
We maintain a list of drone cameras and their physical sizes here (obtained via varying methods mentioned above):
Contribute to Theta-Limited/DroneModels development by creating an account on GitHub.
github.com
We are proactive in maintaining this list for as many new drone models as we can and encourage community contributions for users wanting to make their own drones compatible with our (or others') software.
If you multiply ccdWidthMMPerPixel by widthPixels for any drone in this list, this will give you the sensor width for example. Same for height.
For the focal length you're looking for, it is usually stored within EXIF metadata by photos taken with a given drone. I recommend
Phil Harvey's ExifTool for Windows or
Exiv2 on Mac and Linux. Example usage:
You can probably calculate the FOV based on the tan(1/2 sensor height (or width) / focal length) * 2
According to the pinhole camera mathematical model:
Part 3 of the comprehensive tutorial series on image formation and camera calibration in Python
towardsdatascience.com
Feel free to post here or reach out to us at
[email protected] if you have any questions on these processes
www.pilotbyte.com
