How to Talk about Art (Value)

I feel like value is the most important aspect of an image.  That's probably why I saved it for last in my three part series How to Talk about Art.   Value is what leads the viewer's eye to the focal point.  Without value your eye wanders aimlessly.  The best way to see value is to squint.  In fact, the best way to see anything is to squint.  It is how artists see the basic shapes when they draw from life.  

Greg Manchess
Not sure of title or date.

This is one of my favorite images.  It is arresting because it makes my eye go directly to the astronaut's face, which seems to have a look of awe on it.  Here's the reason why.

When you look at it in gray-scale, it is easy to see the darkest value is the astronaut's suit.  It's basically black.  This contrasts with the value of the astronaut's helmet, which is basically white.  My eye goes straight to the area's of greatest contrast, (so does yours!)

Even when this image is blurred-out you can still make out everything because each shape has it's own distinct value.  The astronaut is extremely dark.  His helmet is extremely light.  The planet he is on is a lighter mid-tone whereas the planet in the distance is a darker mid-tone.  The sky is almost as dark as the astronaut.