# Size of the pixel in world units

I am working on 3d max 2019 and I am facing a problem which is knowing the size of the pixel in world units of the images acquired from a free camera or physical camera in 3d max 2019. These parameters are important when working on 'Camera Calibration' subject, particularly the intrinsic matrix as explained in the link below:

https://uk.mathworks.com/help/vision/ug/camera-calibration.html

its true that sensors size in 3d max are available (width *Height) but there is no mention of the image resolution so the size of the pixel can be worked out. . I tried to look for that info and always get posts about pixel dimension which is basically the size of an image in pixels and not the size (width and height) of the pixel itself. Because I have a student license, no technical support is permitted but instead the experts in the community forum. I already asked in the forum but no solution so far. I would really appreciate it if someone has faced the same problem or knows how to solve it

regards

• Pixel have no physical size. – Scott Dec 6 '18 at 22:42
• I'm not sure what are you asking here. You can setup the camera aperture settings (filmback actually) in the Render dialog, the sizes there (WxH) are in pixels. Your question makes no sense. – Luciano Dec 7 '18 at 9:05
• @scott, well it actually does. you can check any lecture about camera projection and specifically camera matrix term to know that it does. for instance, if you want to calculate the length of the pixel you can get from: length of the image in pixels/ length of the sensor in world unit . you can check this link for more info. ephotozine.com/article/… – Caezar Dec 7 '18 at 16:57
• @Luciano I want to calculate the pixel size(individual) not the image size (resolution) in pixels. if you check the link in the post and go to the intrinsic matrix, everything will make sense for you. – Caezar Dec 7 '18 at 17:06
• Pixels have no physical size. The exact same number of pixels can fit a 4" phone or a 30" monitor. There's no "real world' measurement to be made of pixels themselves. It's only when a specific number of pixels are placed into a specific width and height that one can glean the size of a pixel. i.e. 10pixels in 1x1 centimeter square means each pixel would be 1x1mm in size. But the same 10 pixels in a 10x10cm square would mean each pixel is then 1x1cm in size. – Scott Dec 7 '18 at 18:00

I read the linked document, and it makes not much sense to me.

The only thing I would mention.

You can have a sensor of let's say in round numbers 36 x 24 mm. You still can not know the pixel size, you need to define the Mpx.

If your camera is really old and you only have 360x240 pixels on that sensor, then your pixel NOW measures 1/10 mm.

If you have a more modern sensor, of 3600x2400 px, NOW the pixel measures 1/100 mm.

I do not know if that makes sense. I read the link you provided and I do not understand why they need that data. Probably it is to simulate some aberration like diffraction per pixel. But in my opinion, that should be auto-calculated given only sensor size and pixel count or Mpx.

• I agree with you, the problem here is I am working with 3D Max camera, simulation, and the only known parameter is the sensor size. Therefore I need to know either the pixel size or the pixel count and that's the point of the post. – Caezar Dec 9 '18 at 15:51