View Range has no relevance of its own, its only purpose is to serve as a factor for calculating the spotting range.
The maximum possible view range you can currently (v0.7.3) achieve in game is nearly 598.842m with a Patton and 100% Commander and crew having the Brothers in Arms perk, the Commander having 100% Recon skill, the Radio Operator having 100% Situational Awareness skill, the tank having Improved Ventilation and Binoculars equipment installed and using Case of Cola premium consumable.
Minimum Spotting Range
You will always spot any vehicle that comes within 50m of you, regardless of line of sight. Because you do not need line of sight, this is also called proximity spotting, and can be used on certain maps to spot enemies going past a choke-point without actually being being exposed to them.
Maximum Spotting Range
You can never spot a vehicle further away than 445m, the game engine performs no spotting checks past this boundary. Note that unlike draw distance limits, spotting range limits are the same in all directions (think of a virtual bubble instead of a cube).
Rate of Visibility Checks
You will not necessarily spot an enemy tank as soon as you have line of sight on it. The rate of visibility checks is limited as follows:
within 50 m range - every 0.1 sec
within 150 m range - every 0.5 sec
within 270 m range - every 1.0 sec
within 445 m range - every 2.0 sec
The rate limitation on visibility checks means that it is entirely possible that a hidden tank moves out of cover right after a visibility check, shoots you, and returns back into cover right before the next visibility check, thus never getting spotted and staying hidden. This can also lead to fast tanks getting spotted only closer to you than your spotting range would normally allow - at a maximum speed of 72 km/h a tank can cross 40m between spotting checks past 270m range.