Machine vision cameras vs. webcams – final result

We know now that a webcam, thanks to its Bayer filter, has a lower resolution than a machine vision camera, but that’s not the end of the story. The other big difference is in the optics.

Webcams use a diddy little plastic lens with a tiny aperture and a focal length so short that it’s almost a fisheye. In contrast, a ‘C’ mount lens, with its much larger diameter, allows more light through to the sensor. It also creates less distortion because it has large glass elements rather than plastic.

Less distortion? If you flip back to the images posted at the start of this discussion, “Webcam versus machine vision cam,” you’ll see how the machine vision camera exhibits the curved vertical lines characteristic of a wide angle lens. So why doesn’t the webcam image show the same?

To be truthful with you, I don’t know. My guess is that there are other elements in the optical path that correct this out, but if so, they will further reduce the amount of light that gets through. The alternative is that a software correction is being applied, perhaps right in the camera.

In conclusion: the success of your vision application relies above all on the quality of the images acquired, so put down that webcam and spend a little extra on a proper machine vision camera and matching lens.