Some comparative figures:
- With SST-20 4000K at standard driving current (R27 sense resistor), maximum power at the emitter: 350mA × 2.77V = ≈0.97W (check typical SST-20 4000K Vf in djozz's test, see below).
- With XP-E2 red at increased driving current (R20 sense resistor), maximum power at the emitter: 472.5mA × 2.12V = ≈1.00W (check typical XP-E2 red Vf in djozz's test, see below too).
Since the calculation is done for the standard red emitter, it is also fully valid for the photo/deep red one (its Vf may even be a little bit lower). 