Question regarding pixel size

[fsteiner]

Hello community,

in the camera calibration settings, I can set the pixel size (mm). I have two questions regarding this vaule:
1. Which pixel size is of interest? Many cameras have a higher density of pixels on their actual sensors than the resulting pictures will have (effevtive vs. total). Which value should be used?
2. At which point in the calculation is this value used? What does it change, when adding the value in the end? Which steps need to be redone?

Best regards.

[Alexey Pasumansky]

Hello fsteiner,

In the camera calibration dialog the Pixel Size stands for the sensor pixel pitch size (usually few microns). This value along with the focal length in mm is derived from image EXIF, if present.
Both values are used for Initial values estimation to be used in autocalibration procedure, so they shouldn't be very accurate.

[fsteiner]

Thank you for this answer,

Just to make sure I get this right: If the pixel size is used for the initial calibration estimation, it wouldn't improve anything, when adding these values in the end? Or in other words: If the initial alignment and the camera calibration work fine, the pixel size/pitch is not necessary?

Thank you very much,
- fsteiner

[Alexey Pasumansky]

Hello fsteiner,

It's correct. These values (focal length and pixel size in mm) are used to calculate initial values if Auto option is turned on. So if you change the values after the alignment is finished, it wouldn't effect on anything (unless you are using Fixed calibration option and then optimize the alignment).