Using deep J , H and K _ { S } -band observations , we have studied the near-infrared extinction of the Nuclear Bulge and we find significant , complex variations on small physical scales .
We have applied a new variable near-infrared colour excess method , V-NICE , to measure the extinction ; this method allows for variation in both the extinction law parameter \alpha and the degree of absolute extinction on very small physical scales .
We see significant variation in both these parameters on scales of 5 \arcsec .
In our observed fields , representing a random sample of sight lines to the Nuclear Bulge , we measure \alpha to be 2.64 \pm 0.52 , compared to the canonical “ universal ” value of 2 .
Our measured levels of A _ { K _ { S } } are similar to previously measured results ( 1 \leq A _ { K _ { S } } \leq 4.5 ) ; however , the steeper extinction law results in higher values for A _ { J } ( 4.5 \leq A _ { J } \leq 10 ) and A _ { H } ( 1.5 \leq A _ { H } \leq 6.5 ) .
Only when the extinction law is allowed to vary on the smallest scales can we recover self-consistent measures of the absolute extinction at each wavelength , allowing accurate reddening corrections for field star photometry in the Nuclear Bulge .
The steeper extinction law slope also suggests that previous conversions of near-infrared extinction to A _ { V } may need to be reconsidered .
Finally , we find that the measured values of extinction are significantly dependent on the filter transmission functions of the instrument used to obtain the data .
This effect must be taken into account when combining or comparing data from different instruments .