To make an image like a sketch in Photoshop

• Go to photoshop
• load any image
• press ctrl + J to make a copy of it
• now click the button shaped like a half-circle below
• select hue/saturation
• make saturation to 0
• now select layer 1

• Click the tab where written normally
• select the color dodge
• now press ctrl + i to invert the color
• now go to filter -> blur -> Gaussian blur
• select the blur accordingly
• now click the icon on the right size shaped like audio line named as level and set the level accordingly
• now use the brush tool to make the image more enhanced by changing the opacity to 40 %