I believe that the confusion stems from the fact that the presence of a mechanical shutter does not always guarantee that linear rolling shutter distortion is not present in an image. In fact, the sensor in the DJI Phantom 4 Professional camera is a CMOS sensor that records each image line-by-line, as Brian mentioned, which is typical for a rolling shutter , and not “all at once” which is characteristic of a global shutter.
For additional information about the camera sensor and the shutter itself, we recommend contacting your camera’s manufacturer directly.
We have reason to believe that whatever rolling shutter distortion that may be present in images captured by DJI’s Phantom 4 Professional is, generally speaking, marginal and should have little to no effect on your project results.
However, if you see any symptoms in your project that are commonly due to excessive amounts of linear rolling shutter distortion in your images, e.g. your results bending or an extreme difference between your camera’s initial and computed internal camera model parameters, etc., we recommend the following:
- Enable the linear shutter optimization in the Image Properties Editor and then process step 1. Initial Processing again.
- Capture the project area again while flying slower and/or higher above the ground to reduce the amount of linear rolling shutter distortion that is present in your images. You can see how your camera and flight parameters influence the amount of linear rolling shutter distortion that is present in your images with Pix4D’s Vertical Pixel Displacement Calculator.
- Ensure that the Mechanical Shutter option in DJI GO 4 is enabled for all future flights. Please note that enabling this option does not guarantee that all images will be captured using the mechanical shutter due to limitations of the mechanical shutter’s exposure time and other factors.
Please do not forget that it is not possible to identify the presence, absence, or amount of linear rolling shutter distortion that is present in an image simply by looking at it. A common misconception is that a blurry image is caused by rolling shutter distortion. The geometric distortions that are introduced into an image by a linear rolling shutter cannot be identified accurately by the human eye so if you have a camera with a linear rolling shutter and do not have a general idea of how much distortion is present in your images, we recommend that you at least estimate how much distortion is present with Pix4D’s Vertical Displacement Calculator.
To be clear, the factors that influence the amount of linear rolling shutter distortion in an image are not the same factors that influence whether an image is blurry.