STScI Calibration Data System

WFPC2 Pixel Area Correction Table

NOTE:

Do not use this correction file if you plan to use Multidrizzle, as all geometric distortion corrections, including the pixel area correction, are properly accounted for in the software.

When performing integrated photometry, users should be aware that WFPC2 has significant distortion which causes the pixel area to vary across the field. The application of flat-fields "corrects" for this and normalizes all pixels to have the same area. However, this renders integrated photometry incorrect, because all of the light falls on the distorted pixels and correcting for the pixel area changes the amount of total light.

Consequently if you are measuring integrated brightnesses (as opposed to surface brightnesses), you will want to put back the true relative pixel areas. Maps of these can be found below. Multiply by these maps to put the relative areas back into the image. The maps are normalized to unity at (400,400) in each chip.

File Use After Mode Gain Pedigree Comments
f1k1552bu 12-01-1993 00:00:00 FULL N/A INFLIGHT Relative pixel area correction map