CMOS sensor inventor Eric Fossum gives a terrific lecture at his alma mater Yale University and you can catch it on YouTube.
The title of this post is from that film at around the 39 minute mark and he suggests that it is one of his favorite sayings.
What it specifically refers to is the fact that the best optics can focus down to a useful point size of about 4.4 microns. That’s pretty small, but today’s cell phones and small sensors have much higher pixel density than that in order to be able to advertise 16mp resolution in a camera phone (yes, he showed an image of the assembly from Sony that has that ability.)
And such densities mean that pixels are down to 2 or even 1 micron in size, which means of course that the camera is diffraction limited (i.e. images will be soft) right out of the box, no matter how good the optics are.
And his point is that, if the number on the box is bigger, the item will sell. Thus, marketing has more influence than engineering.
Physics is working against you, and he says that it is “not so easy to fix, but it pays the bills for us engineers and gives us something to do …”
If you are interested in how CMOS devices have evolved and how they work, this is an excellent talk. Note: He also goes into the myriad social and societal implications of having ubiquitous imagery and high speed computing to analyze it … so if you have interest in social issues, watch at least the first part.