varies as the 6.2 and 7.7[$\mu$m]{} PAH features move within the passbands. This variation in flux ratios is illustrated in Figure 3 for four different SED types derived from spectral observations of galaxies in the local Universe [@Armus; @Brandl:04].

While it is true that variation of PAH line ratios or strength of silicate absorption can cause broadband fluxes to vary significantly, the combination of photometric redshifts from the optical/near-infrared and mid-infrared photometric redshifts using these three bandpasses can help break redshift degeneracies.

The flux density ratios observed for HUDF-JD2 are a 16[$\mu$m]{}/22[$\mu$m]{} ratio of 0.25$^{+0.19}_{-0.08}$ and a 22[$\mu$m]{}/24[$\mu$m]{} ratio of 1.1$^{+0.37}_{-0.13}$. This indicates that the galaxy must either be at $z\sim0.6$ if it has very strong silicate absorption or at $z\sim1.7$ if it is a typical starburst galaxy with strong PAH emission.

In Figure 4 and Table 1, we illustrate the quality of fits to the photometry at 16, 22 and 24$\mu$m from different mid-infrared template spectral energy distributions. We consider starbursts, AGN and composite sources which span the range of strong PAH, weak PAH and strong silicate absorption [@CE01; @FS01; @lef:01; @Dale:02; @Brandl:04; @Armus]. We also consider the non-detection of JD2 in deep 70[$\mu$m]{} observations of the GOODS fields 