A Comparison Between NSFCAM2 and SPEX
                                 NSFCAM2           SpeX Guider
Pixel scale                   0.04"                    0.12"
FOV                            80x80"                 30x30"
Gain                            4e/DN                 12e/DN
Full well                   ~65,000 DN        ~ 3,000 DN
2% linearity             < 25,000 DN        < 2,000 DN
Readnoise (CDS)    44  e RMS             40 e RMS
Readnoise limit      ~44 e RMS            ~20 e RMS
Approx. sensitivity     5sigma     (Vega mags) (Seeing dependent)
J  540s                         19.3           20.4
H  540s                        19.6           19.8
K  540s                        18.5           19.1
L'  90s                          14.0           13.2
M'  92s                         10.8           saturate
Due to the engineering-grade quality of the array currently in NSFCAM2 its photometric performance is limited compared to the old NSFCAM. The two issues are higher than nominal readnoise and an excessive number of bad pixels. See the section on NSFCAM2 sensitivity  for the effect of the higher read noise on sensitivity.
The excessive number of bad pixels increase the difficulty of obtaining good photometric precision (~1%). Tests on bright stars (JHK < 8 mag) dithered on the array indicate that precisions of 1-2% are achievable using daytime sky flats and replacing bad pixels using a mask. However, the precison degrades for fainter stars. (Note that
integration times for daytime sky flats are 5s at J, 8s at H. and 30s at K). Sky (or dome) flats do not work in the thermal (L' and M'). At these wavelngths dither the object and standard to reduce the RMS error or put object and standard at the same location on the array.
Consequently we recommend that observers use SpeX for JHK imaging photometry. See the SpeX webpage for the sensitivity and photometric performance of the SpeX guider. For high background applications (e.g. L' imaging, Jupiter imaging) NSFCAM2 is superior since the background dominates the readnoise and noisy bad pixels. Due to the finer pixel scale NSFCAM2 images (0.04") have slightly better spatial resolution than SpeX images (0.12")."