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Every year comma beginning with the SMOV comma ACS-WFC has obtained multiband imaging of a moderately crowded stellar field in the globular cluster 47 Tuc (about 6. west of the core). Measured stellar positions and magnitudes are used to monitor local- and large-scale variations in the plate scale and the sensitivity of the detectors. Single exposures in each WFC subarray mode (512 comma 1K comma 2K) allow us to verify that photometry obtained in full-frame and in subarray modes are repeatable to better than 1%. These observations will help validate and monitor the Cycle 24 redefined ACS subarray readouts comma which now include all pixel columns for consistent timings. Although the new 512 comma 1K comma and 2K subarrays are defined for all 4 readout amplifiers comma the B amplifier subarrays are the current default for subarray requests comma and the default for the WFC polarizers. This program will obtain only B-amplifier subarray exposures. Cycle 30 will be the fourth year of consecutive observations of Omega Centauri globular cluster with standard ACS-WFC filters (in the same way as 47 Tuc). This cluster is a WFC3-UVIS calibration target. These ACS observations will be used for comparison of L-flat and filter-dependent distortion for ACS-WFC and WFC3-UVIS.