Canon cameras are modified by removing the LPF2 filter to open the sensor to H-alpha light. The LPF1 filter is retained and it acts as a UV/IR cut filter and the dust removal tool. The sensor position is precisely calibrated afterwards to allow for the internal autofocus system to work properly.
Full spectrum modification
For a full spectrum modification, all filters in front of the sensor are removed to open it to the entire light spectrum, including UV and IR. External filters with UV/IR cut capability are required for this modification type. Popular camera models for this modification – Nikon D5300/D5500/D5600, any Canon camera.