Light available for photosynthesis fluctuates continuously in the field, as clouds cross the sun and as the movement of the sun causes shadows to move across leaves. Transgenic manipulations to allow more rapid relaxation of non-photochemical quenching during sun-shade transitions increased productivity in the field by 14-20%. Rubisco activation is a key limit on photosynthesis during induction following shade-sun transitions. This suggests there may also be potential to increase photosynthesis and crop productivity by speeding up Rubisco activation.