  The statistical power of weak lensing measurements is principally driven by
the number of high redshift galaxies whose shapes are resolved. Conventional
wisdom and physical intuition suggest this is optimised by deep imaging at long
(red or near IR) wavelengths, to avoid losing redshifted Balmer break and Lyman
break galaxies. We use the synthetic Emission Line EL-COSMOS catalogue to
simulate lensing observations using different filters, from various altitudes.
Here were predict the number of exposures to achieve a target z > 0.3 source
density, using off-the-shelf and custom filters. Ground-based observations are
easily better at red wavelengths, as (more narrowly) are space-based
observations. However, we find that SuperBIT, a diffraction-limited observatory
operating in the stratosphere, should instead perform its lensing-quality
observations at blue wavelengths.
