We present new infrared JHK photometry for 61 halo and disk stars around the stellar/substellar boundary .
We also present new L ^ { \prime } photometry for 21 of these stars and for 40 low–mass stars taken from the Leggett 1992 photometry compilation .
These data are combined with available optical photometry and astrometric data to produce color–color and absolute magnitude–color diagrams — the current sample extends the similar work presented in the 1992 paper into more metal–poor and lower mass regimes .
The disk and halo sequences are compared to the predictions of the latest model atmospheres and structural models .

We find good agreement between observation and theory except for known problems in the V and H passbands probably due to incomplete molecular data for TiO , metal hydrides and H _ { 2 } O .
The metal–poor M subdwarfs are well matched by the models as oxide opacity sources are less important in this case .
The known extreme M subdwarfs have metallicities about one–hundredth solar , and the coolest subdwarfs have T _ { eff } \sim 3000 K with masses \sim 0.09M/M _ { \odot } .
The grainless models are not able to reproduce the flux distributions of disk objects with T _ { eff } < 2500 K , however a preliminary version of the NextGen–Dusty models which includes homogeneous formation and extinction by dust grains is able to match the colors of these very cool objects .
The least luminous objects in this sample are GD165B , three DENIS objects — DBD0205 , DBD1058 and DBD1228 — and Kelu-1 .
These have T _ { eff } \sim 2000 K and are at or below the stellar limit with masses \leq 0.075M/M _ { \odot } .
Photometry alone can not constrain these parameters further as the age is unknown , but published lithium detections for two of these objects ( Kelu-1 and DBD1228 ) imply that they are young ( aged about 1 Gyr ) and substellar ( mass \leq 0.06M/M _ { \odot } ) .