Why step back ten feet from your painting and then squint?

Why do artists close one eye and squint with the other to look at their painting? Why do artists stand back to look at the painting they are working on?

Artists do those two things for different but related reasons. Both techniques help them stop seeing details and start seeing the overall visual effect.
Why artists close one eye and squint with the other
(See a visual example at the bottom of this post).
Closing one eye and squinting reduces the amount of visual information reaching the brain.

• Closing one eye eliminates binocular vision (depth perception). A painting is a flat, two-dimensional surface, so removing depth cues helps the artist judge the picture as a flat arrangement of shapes and values.
• Squinting blurs the image. This reduces fine details and color differences while emphasizing:
  • Light and dark values
  • Large shapes
  • Overall composition
  • Major edges

When you squint:

• Dark areas appear to merge together.
• Light areas merge together.
• Small details disappear.
• You can quickly see whether the painting reads well from a distance.

For example, if a face only looks convincing with every eyelash and wrinkle visible, squinting will reveal that the underlying light-and-shadow pattern isn't working.

Why artists stand back
When you're painting, you're often only 12–24 inches from the canvas. At that distance, you're concentrating on tiny brushstrokes and details.
Stepping back 6–15 feet lets you judge:

• The overall composition
• Balance of light and dark
• Whether the focal point attracts attention
• Whether perspective feels correct
• Whether colors harmonize
• Whether one area is unintentionally dominating the painting

It's similar to reading a paragraph: if your nose is one inch from the page, you can see individual letters but not whether the paragraph communicates well.

The combination is powerful
Many experienced painters repeatedly follow this cycle:

1. Paint up close.
2. Walk back several feet.
3. Squint with one eye.
4. Notice the biggest problem.
5. Walk forward and fix only that problem.
6. Repeat.

This prevents becoming absorbed in details before the large visual relationships are correct.

A useful saying
Many painting instructors teach:
"Work from the general to the specific."

​Squinting helps you see the general, while standing back helps you judge the whole. Only after those are working well do the specific details make the painting stronger.

Notice as how the blocked-in version above looks more like the blurry version above it. That's a good thing because it captures the overall structure of the subject. Then, after the block-in, the artist can continue moving toward the details. But going for the detail first unnecessarily complicates what the artist is looking at. It's better to block-in first.