Near-Infrared Photometry
The 2MASS photometry is converted to the WINGS/WFCAM photometric system with and then compared with WINGS magnitudes, for the whole collection of our NIR mosaics, separately in J- (upper panel) and K-band (lower panel). The absence of a significant zero point shift and the relative tightness of the magnitude sequence demonstrates the quality of the photometry in the WINGS-NIR survey.
Photometric errors assigned by SExtractor are unrealistically small, because they are based only on the photon-noise statistics. Here we present the global results (J and K band together) of photometry checks from the simulations. 
In the top panel the differences between input and output SExtractor MAG_AUTO magnitudes as measured from the mock images for stars (red
starred dots), exponential disks (open magenta circles) and spheroidal r1/4 (blue filled circles) are plotted for 0.5mag bins. The agreement is quite good, apart from
the constant shift of 0.2mag for spheroidal galaxies even at
bright magnitudes, a well known effect caused by the loss of light from the wings of profiles of spheroidal r1/4 galaxies in the background noise. The bottom panel of the same figure presents the overall precision of our
photometry (the RMS of measurements is plotted for 0.5mag
bins, the symbols are as above), with the corresponding polynomial fit for spheroids (blue line) and exponential disks
(magenta line) to be used as RMS value for all magnitudes of the catalogs.
Color magnitude diagrams of classified galaxies for a selection of WINGS-NIR clusters. The relatively thin red cluster sequences confirm the accuracy of the photometry provided by SExtractor. The large number of detections obtained at fainter magnitudes are the field background galaxies and demonstrate the deepness of our survey. There are also indications of red sequences for the field galaxies at bright magnitudes, indicating the presence of background clusters at higher redshift. The big red full circles are the spectroscopically selected members of the clusters(the RMS of the spectroscopically confirmed members of the clusters is 0.03mag and 0.05mag).