Image sensors continuously develop in-field permanent hot pixel defects over time. Experimental measurements of
DSLR, point and shoot, and cell phone cameras, show that the rate of these defects depends on the technology (APS or
CCD) and on design parameters like imager area, pixel size, and gain (ISO). Increased image sensitivity (ISO) enhances
defects appearance and sometimes results in saturation. 40% of defects are partially stuck hot pixels, with an offset
independent of exposure time, and are particularly affected by ISO changes. Comparing different sensor sizes with
similar pixel sizes showed that defect rates scale linearly with sensor area, suggesting the metric of defects/year/sq mm.
Plotting this rate for different pixel sizes (7.5 down to 1.5 microns) shows that defect rates grow rapidly as pixel size
shrinks. Curve fitting shows an empirical power law with defect rates proportional to the pixel size to the power of -2.1
for CCD and to the power of -3.6 for CMOS. At 7um pixels, the CCD defect rate is ~2.5 greater than for CMOS, but
for 2.4um pixels the rates are equal. Extending our empirical formula to include ISO allows us to predict the expected
defect development rate for a wide set of sensor parameters.