Word for viewing angle

What is a word for viewing angle? For example,

The color of a birefringent surface varies with angle you look at it from.

It would be something like attitude or aspect.

Solution 1:

Perspective, view point, or point of view. "Point of view" has become a common term. I've seen the acronym POV used in various instances, particularly film direction.

I just recognized the scientific context of your question so I'd like to amend my answer slightly. If the original "viewer" can represent something other than human, then "Angle of attack" might be appropriate. This is a term used in medical imaging to describe positioning.

When taking radiographs for instance, one attempts to position the x-ray generator and detector plate in perfect alignment within the same plane. If either the plate or the generator tilts before or during the exposure, the image will be affected and the radiologist who reviews it may determine the image was poor because the "angle of attack" was not perfect.

Solution 2:

If it's a technical topic I would go for the more precise term over the most fluid prose.

Viewing angle or 'angle from the normal' would be correct, point of view, perspective, etc would either lead to confusion by experts if there is already a specific meaning for the term or by everyone else if they are left wondering if your 'perspective' is the same as the 'angle of view' they learnt somewhere else