I've been struggling to sketch a portrait from a magazine. Beautiful model, head tilted back, photographed from below, not too much light and shade. It doesn't look like a hard subject but my first attempt looked like a hideously deformed dwarf.
Then it dawned on me I was forgetting about perspective. The rules of proportion only apply when the subject is viewed straight on at a level plane. Once you alter anything, like a turn and tilt of the head or drop below the horizon line the image distorts accordingly. What is closer appears larger. Like a terrace of houses, all the same size, petering away into the distance when viewed from the end of the street.
The odd thing is our brains are so accustomed to processing the images we see that they automatically allow for the effects of perspective so that we are no longer conscious of it. I'm having to train myself to override this faculty to draw what I see rather than what I know is there.
I think this same loss of vision happens whenever we're too close to or familiar with something. It may explain the myopic views of some publishing professionals faced with the changes happening at the moment. After all, it's hard to see something afresh when you've looked at it unthinkingly for many years.
As my sketching problems clearly show.