Recent content by Mark Dresser

To think about this another way: You can easily demonstrate that if you have a square source that occupies 16 pixels in your detector field of view and you double the viewing distance it will occupy 4 pixels. If the ISL applies then the total energy hitting the entire detector array also drops...

Thanks all for your input. I like jbriggs444 explanation "So if the image illuminates multiple pixels, the inverse square law manifests in terms of the number of pixels illuminated." I think I'm satisfied enough to move forward on an experiment to test it!

I am thinking of two extreme cases and ignoring everything in between: 1. a point source with a detector with a very wide field of view. ISL clearly applies. In the lighting industry they use a rule of thumb that for distances greater than 5x source size ISL is a good enough approximation but...

The source would typically be a large slab of hot steel, 20 - 30 m from the camera. Focussing is done with a commercial camera lens. The light source is many pixels wide at all of the distances in question.

I am interested in evaluating light intensity variation in a digital image. A colleague wants to apply an inverse square law correction to account for distance variation. I am trying to justify that in this case, the inverse square law does not apply. Treating each pixel as a detector, it has...