[ITAL]VI[/ITAL] Photometry of Nearby Globular Clusters: M3, M5, M13, and M92

( V , V - I ) color-magnitude diagrams (CMDs) are presented for the four nearby globular clusters M3, M13, M5, and M92. These clusters span the range -1.3 > [Fe/H] > -2.3, and the new CMDs are intended for use as templates against which to compare the outer halo clusters observed with Hubble Space T elescope F555W and F814W filters. The calibration to the system of Landolt appears to be secure to ≲1%–2%. Comparing M3 with M13, it seems unlikely that the clusters differ in age by the 2–3 Gyr required to explain the difference in their horizontal-branch (HB) morphology purely as an age effect. If the HB difference is to be attributed to a single agent, we propose that a difference in Y of ∼0.05 (with M13 having the larger Y ) would most economically explain the differences in the main-sequence turnoff and HB morphology between the clusters.