The loss of through focus process latitude due to the interaction of electromagnetic fields that are at 90 degree phase with the intended 0 degrees and 180 degrees at mask edges and line-ends is characterized for 45 nm imaging using thick-mask and image simulation. TEMPEST and Panoramic Technologies simulators are used to determine near fields and images of chromeless, MoSi and Ta-SiO2 line ends. These fields are then analyzed in both space and plane wave spectra to determine rules of thumb for the effective narrowing (real) and leakage (quadrature) contributions in boundary layers to improve the accuracy of thin-mask models. Typical values for ATT-PSM are 0.05 to 0.1 lambda/NA per edge. These values varied only slowly out to angles of incidence on the mask of 20 degrees suggesting an angle independent boundary layer parameter would be moderately accurate. For chromeless the values are larger and can be over 0.2 lambda/NA per edge for the quadrature component. The through focus imaging for lines and line ends is then made using the full set of near fields, producing a tile of the Bossung curve through focus that is 18 nm for line-end shortening. The Ta-SiO2 mask stack showed more irregular behavior compared to the other masks.