H-R diagram for our sample of binary system. Each pair (red and blue circles) has been joined by a line, and the discovery designation is noted. The bar at (−0.1,+6.0) shows the estimated error of the photometry, as discussed in Section 2. For YSC8, BU220, and I253AB we also show our “corrected” magnitudes (red and blue diamonds), obtained from our Δy measurements as explained in Section 3.3. Clearly, these latter agree much better with the theoretical isochrone. See text for details and comments on individual systems.