r and Hα emission of a detection with homogeneous and relatively low background noise (NGC 3336, top), and a lower limit with uncertain continuum subtraction and inhomogeneus background noise distribution (LEDA 761585, bottom). In particluar, LEDA 761585 is the galaxy with the lowest S/N in the sample (S/N ≃ 6). The green ellipse represents the r26 magnitude isophote in which we performed the photometry. The white regions had negative emission due to uncertain coontinuum subtraction, and were masked and set to background emission levels. Idem for the blue regions, masking bright stars.