Notes:

before any measurements will be made at least one of the catalogue parameters RAD0 through RAD15 must be present in the default.param file. The minimum starting threshold that can be used is the analysis one -- no information about values below this is available.

For completeness the existing ISO0-ISO7 areas in SExtractor are based on an optimal sampling of each object profile. Under this scheme each threshold is:

$I_{i} = start * (\frac{I_{p}}{start})^{i/8}, \ i = 0, 7$

where $I_{p}$ = peak intensity. So you get a range of levels for each object spanning the range from its analysis threshold to just below the peak intensity.