Top: broad-band colours and the excess in the NBC iv: (i′−NBC iv) versus (R_c − z′) (left) and (i′−NBC iv) versus (R_c − i′) (right). Colours, symbols and contours are the same as in Fig. 4. The green dashed lines indicate the boundaries of the LAE colour selection criteria. Bottom left: (i′−NBC iv) versus NBC iv colour–magnitude diagram. Vertical dashed and dotted lines indicate the NBC iv 5σ-limiting magnitudes of field J1030+0524 and field J1137+3549, respectively. Many broad-band selected sources are not detected in the NBC iv band and are assigned the corresponding 1σ magnitude limit (NBC iv_1σ ∼ 27.4–27.5 mag). Bottom right: (i′ − z′) versus z′ colour–magnitude diagram. Vertical dashed and dotted lines indicate the z′ 5σ-limiting magnitudes of field J1030+0524 and field J1137+3549, respectively. The horizontal dashed line shows the i′-dropout boundary (i′ − z′) = 1.3. LAEs have fainter broad-band UV magnitude than LBGs.