Thumbnails can be useful as a warmup exercise, time efficiency, fast iterations and problem solving. I personally found these exercises for today challenging since I tend to spend way too much time creating thumbnails, I would spend at least 1-3 hours to create one thumbnail and this is very time consuming. Working in grayscale can vary depending on what I want to achieve, the value usually comes naturally for me when it comes to the light, mid and dark tones. Although using the Rule of Thumb was helpful and I will definitely use it for my future thumbnail drawings.

Three landscape images with 3 basic values, identifying foreground, midground and background.