The evolution of the luminosity function of clusters of galaxies at
redshifts of 0.2 < z < 0.6 is studied, using the NOT telescope. Using
subtraction technique, we have determined the R-band luminosity function
for MS2255.7+2039 at z=0.29 down 
. It is found that, in agreement
with clusters at lower redshift, the luminosity function is considerably
steeper than a standard Schekter luminosity function at the faint end, as
predicted by hierarchical clustering scenarios.
We have also studied a distant cluster at z=0.54 in U, B, V, R and I in order to test the use of photometric redshifts to select cluster members for determination of the luminosity function, as well as color variations within the cluster. Observations have been obtained at NOT and we have also made simulations to determine the accuracy of this technique as the limiting magnitude is approached. As a spinoff, one should also be able from the colors to find distant background objects, using the Lyman break method.