Ever wondered why precision camera lenses cost so much? The amount of micro-level detail that goes into it is incredible. 

From doing CAD designs, creating and shaping the glass, machining the lens barrels to ultra-fine tolerances, adding electronics, waterproofing and finishing – it's a long process that is well documented in an interesting 24 minute video by YouTube channel Process X.

Within the first five days of uploading the video - there have been more than one million views!

We also can't speak for all lens manufacturers, but it's remarkable how much of the process is done by hand, even with huge advances in automation. 

You can learn more and see the current line up of Sigma lenses on their official website here.