Home : Photoshop Retouching : Hue/Saturation
With Hue/Saturation, we can achieve grayscale result
by sliding the saturation point to the extreme left.
1. Open an image to for grayscale output.
2. Image > Adjustments
> Hue /Saturation
3. Drag the Saturation slider as shown in the image.
4. You will get the following output.