Down To Business
Don’t worry if all of these concepts are a little foggy. F-stops in particular will take some practice - you know, while holding camera - to get used to.
In other words, I know you might be confused! Relax! I just threw a whole lot at you, so just relax. Breath. Take a few photos at different apertures [[link to section on aperture priority mode]]. Let’s review the important things to remember.
Lenses take light that is bouncing around (as light does), and direct some of it at as an image on an image sensor. The image sensor reads this light and ’takes’ a photograph. They image that is projected onto the sensor can be zoomed in or out by changing the width of the lens, called focal Length. This is usually done by twisting a control around the barrel of the lens. Some lenses have electronic controls, and a motor to zoom in and out for you. This focal length is measured in millimeters (mm) for legitimate reasons that are legitimate, don’t worry about why.
Zooming out means a lower focal length (small mm), and zooming in is a higher mm distance (big mm)
The part of the image that is in focus can be adjusted by adjusting the focus ring on the lens. Most lenses have the focus ring farther forward than the zoom ring, control wise. Twisting this will change the distance away from the lens that objects are in focus. The distance is measured in units of distance (duh). Geet or meters, usually. This distance is the middle point of what is in focus, and the range of distances of what things are in focus is called the “depth of field”.
How much light that gets to the image sensor can be adjusted by changing the aperture of the lens. This is a ring that shrinks and grows. Measured in f-stops, we adjust the ‘f-stop’ in order to change the size of the aperture. This also affects the depth of field.
That Wasn’t Too hard!
Feel free to ignore and forget anything about optics or lens design or square roots. I mention these complicated (and unnecessary) things because when I was learning photography, I was frustrated about how my resources didn’t mention anything about them!
Understanding the design constraints that lenses have won’t make you a better photographer, but it will make you a smarter one. When hunting for lenses on eBay, it’s nice to know why a lens is or isn’t better. Sure, knowing the lowest f-stop and range of width is nice, but what about the coating of the glass? The number of aperture blades? How about how fast the motor can focus an image, or even what type of motor is used? Which lenses are worth their weight, and which are plastic pieces of crap? Or what about a plastic piece of crap that takes really really beautiful images? (I’m looking at you, Holga).
I have covered lenses to a more advanced degree than most introductory guides - but there still is a lot I left out. I encourage you to continue researching.
Lenses are incredibly advanced, sophisticated pieces of technology, and I believe it is a passive benefit to at least learn some of how they work.
The lens is arguable the most influential piece of gear - it will affect how your photos appear photos the most. (Although light sources make a close contender).