Comparison of B-band photometry for known Centaurus group galaxies in our survey area. Values from the literature (for references see Table 3) versus the B-band magnitude we derived from our gr photometry. We adopt a conservative error of 0.4 mag for our data, which includes the uncertainties for both filters. Photometric uncertainties for the literature values were taken from the publications. The unity line is shown as a solid line. For five galaxies the magnitude difference is larger than the error tolerance (indicated in red). These discrepant cases are discussed in the text.