I've always thought that lenses were greatly over-priced. How can they justify the price tages that come with them? It wasn't until I stripped this one down, that I realised just how much technology they contain. The lens shown here is the 50mm 1.8; it is the cheapest lens in the Canon catalogue. I expect that more expensive lenses contain more technology, but I'm not looking to break a more expensive one just to find out.
The true nature of lenses - upside down images.
Proof, if it were needed, that you can reverse a standard lens to take macro images.
This is how it's done. Mine is a poor image bacause I just lined the lenses up, but for less than a tenner you can buy a specially made coupler ring (sorry about the quality of this shot too, but it's hard taking a picture of yourself holding one camera at arm's length whilst looking through another).
The six main parts of the lens laid out. Please hover cursor over the picture for labels. Note, that as this is a very simple fixed lens so there's only two pieces of glass. If anyone fancies dismantling a very expensive zoom lens, I'd love to see how many they have.
The six again, but this time in order from front to back.
The circuit board. I don't know what bits do what, with the exception of the little round disk at the bottom. This controls the flow of electricity into the motor via some brushes on the back.
The drive mechanism. Because it's only a cheap lens, this is made of plastic. The cog in the bottom right hand corner controls the auto focus. When it is disengaged (as in the picture) focus is manual. When it is engaged (imagine it pushed to the left a bit in the picture), the auto focus works.
Same mechanism, different angle.
The motor. The whole thing is just 20mm from top to bottom.
The focussing mecanism. Movement of the plastic block “A” in the groove “B” is what causes the front lens element to move in and out.
The aperture half way open. Being a cheap lens, it only has 5 diagphram blades. Pay more - get more. The slider to the right is what controls the aperture,