Have you ever wondered what is inside a camera lens? No? Well, this blog post might be one that I write for myself only, in that case. But make sure and check out the focus tips I have at the end of the page!
I work better when I understand the mechanics of what happens when I push a button or spin a wheel. So breaking a camera lens gave me the opportunity to tear it apart and inspect what’s inside.
The lens in question is the Olympus 40-150 mm f/4-f/5.6, which I used on my mirrorless Olympus camera. This lens came in the kit when I bought the camera. And, at $179 to purchase separately, it is a surprisingly good lens. Adjusting for the camera’s crop factor, this lens is like an 80-300mm on a 35mm camera.
This lens broke off when I dropped my camera. It wasn’t repairable. So I unscrewed, pried, broke, twisted, experimented, and explored every last piece inside it.
How Does a Camera Lens Work?
Let’s talk about how lenses work before we go any further.
The lens in the diagram above has 9 pieces of glass. Each piece of glass is called an element. Each side of an element can be flat, concave (squished in in the center) or convex (puffed out in the center). Elements are joined together in groups.
Why are lens elements curved?
The job of a camera lens is to take your subject and make it fit on your camera sensor. In most cases, your subject will be much larger than your sensor.
That means that the lens needs to take the light bouncing off your subject and bend it so that it fits onto the sensor AND stays sharp looking. That process looks something like this:
The curved edge of the lens bends the light so that it all fits onto one point. Pretty cool, right?
However, the lens does something else to your subject. Look at the photo below where I shot through a fishbowl that acts like a lens element. What do you notice? Two things jump out at me when looking through the fishbowl:
- The image inside the bowl is upside down.
- The image inside the bowl is distorted.
The arrow is pointing to a curved line that is actually a straight palm tree. Note that this distortion is worse on the outside edges of the lens/fishbowl than it is in the center. The straight lines on the dock look relatively straight.
The lenses in your camera work EXACTLY the same way. First off, the image projected onto your camera’s sensor is always upside down. The camera flips it for us so that we don’t see it that way.
Second, the curved glass in lens elements distorts your subject, especially near the edges of your photo.
Lenses contain multiple glass elements to counteract as much of this distortion as possible and to create a sharp representation of your subject on the camera sensor.
When you focus your camera, some of these elements move closer to or farther away from your camera’s sensor to achieve focus. (Much like I have to move the newspaper closer to and farther from my eyes in the morning before I can read it.)
What’s Inside a Camera Lens?
I knew that my lens had 10 groups with 13 elements. So I was surprised to take out only 4 things that looked like lenses. It turns out that elements, and groups of elements, are much smaller than I expected. This page has a great diagram of the 40-150.
The first group has two elements – this is the outermost part of the lens–the part that you clean before shooting.
Next, I found this tiny piece that contains 3 elements:
The third section is the heaviest of the lot. It’s an inch or an inch and a half tall.
Finally, this last section. You can see the mechanism that helps it move towards or away from the sensor for focusing purposes.
What I was most excited about was the aperture! You can see it opened here:
And closed here:
That silver thing off to the side of the aperture is the motor that powers its opening and closing.
The aperture was much more delicate and insubstantial than I expected. It’s fragile like typewriter tape (you remember that, right?). It feels like very thin plastic-coated paper, or maybe very very thin plastic. It astounds me that we can open and close an aperture so many thousands of times without breaking it.
All lenses are different. The components inside yours might be smaller or larger and made from plastic or glass. But the way it all works together is going to be similar from lens to lens.
What to Do with Lens Elements?
I played with shooting through the various parts of the lens, looking for a through the viewfinder effect. This birdhouse was my subject.
My photos looked like this:
I’ll keep experimenting with using these pieces of a lens to create cool effects.
For Sharpest Focus in Your Photos
What does all this mean for getting the sharpest possible photos on your camera? Check out these articles. They will pull it all together for you:
- How do Cameras Autofocus?
- Sharper Images: Troubleshoot Your Camera’s Focus Problems
- Back Button Focus: A Common Sense Guide
- Photography Focus Tips: Focus and Recompose
- Photography Focus: How to Make Everything in Your Photo Sharp
Now that you know what’s inside a camera lens, you’ll be able to visualize what’s happening in your lens when you follow the tutorials above. Need any more help with focus? Post your questions in the comments below.