Screencast: Photoshop: Transforming Color Images to Monochrome using B&W Filter Layer
Video showing how to convert to monochrome using a Photoshop filter layer.
In diglloyd Monochrome: Photoshop: Transforming Color Images to Monochrome using B&W Filter Layer
At diglloyd Patreon.com: Photoshop: Transforming Color Images to Monochrome using B&W Filter Layer
TIP: watch at 4K on a 5K display for greatest ease of viewing.