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Photography Basics: Lenses

DIY Boudoir Photography Lenses

It’s time to talk about lenses. Knowing how lenses work will allow you to better pick the lens that will give you the results you are wanting out of your photography. In this post we will cover the following topics:

  • How lenses Work

  • Focal Length

  • Lens Mounts

  • Distortion

  • Compression

  • Zoom vs Prime

  • Other Lens Features

  • Glass! Glass! Glass!

How Lenses Work

Lens design is a complicated subject. In basic terms, lenses work by using a series of glass elements in both convex and concave shapes to manipulate light into hitting the cameras sensor in a desired way. I am not the best person to talk to if you want to know the ins and outs of cameras and lenses. If you like knowing the nitty-gritty about subjects and want the same for photography I highly recommend checking out Gerald Undone on YouTube.

Lens Descriptions

When you first start looking at lenses you will see them written like the example below.

Canon RF 24-105mm f/4L IS USM

Each part of this description means something. So let me walk you through it. First, we have the manufacturer of the lens, Canon. Second we have the lens mount type, RF. Third is the focal length of the lens, 24-105mm. Fourth is the maximum aperture of the lens, f/4. Lastly the IS and USM in this lens description tell you it has image stabilization and an ultrasonic motor.

Different lens manufacturers have different ways to describe their lenses so you will have to do a little homework to figure some of them out. But the basic format of brand, mount, focal length, and then maximum aperture will be the same no matter the maker.

You will also see some lenses with Macro in the description. These lenses have very short minimum focusing distances and are helpful in photographing at really close distances. An example of macro photography would be flowers.

Lens Mount

The lens mount is how the lens connects to the camera body. Each camera company has a specific lens mount for their cameras. For example, my Canon RP uses the RF lens mount and my old Nikon d3300 used the DX lens mount.

One thing to look out for with lenses is if the lens is designed for APS-C sensors or full-frame sensors. Some camera companies will use the same mount for both types of cameras. You can potentially damage your camera sensor if you use the wrong lens, so watch out for that.

Focal Length

Focal length is the distance that light will form a cone from the lens onto the image sensor to produce a proper image. You will see this displayed in millimeters (mm). Focal length controls your lenses field of view. The shorter the focal length the wider the field of view. As you increase the focal length of a lens you essentially zoom in on your subject. You will see terminology like wide and telephoto when talking about lenses and their focal lengths. Here is a list of the terminology that refers to a lens’s focal length.

  • Ultra-Wide: Anything Below 15mm

  • Wide: 15mm to 40mm

  • Standard: 40mm to 70mm

  • Telephoto: 70mm to 200mm

  • Super Telephoto: 200mm plus


Things closer to the lens appear larger. This is the entire basis for lens distortion. With shorter focal lengths you will need the subject closer to your lens in order to fill the frame. This means your nose will look bigger at shorter focal lengths than at longer focal lengths. Portrait photographers use a 50mm or 85mm lens most of the time because of this. The 50mm and 85mm focal lengths allow for the least amount of distortion while keeping the photographer close enough to their subject so they can still communicate effectively.


Something you will hear about with lenses is compression. When photographers are talking about compression, they are talking about how you will see less of the background behind a subject at longer focal lengths when your subject is the same size in the frame. Your background will also appear larger at longer focal lengths as well. Go ahead and watch this video to help you understand it better.

Prime vs Zoom

Lenses come in two main types, prime lenses and zoom lenses. Prime lenses have a fixed focal length. For example, my Canon RF 50mm f/1.8 STM has a fixed focal length of 50mm. Zoom lenses allow you to change your focal length and zoom in on your subject. My Canon RF 24-205mm f/4L IS USM lens can go from 24mm up to 105mm and anywhere in between. This gives you a lot of versatility.

With zoom lenses you can have a fixed maximum aperture or a variable maximum aperture. That means as you change the focal length of the lens by zooming in or out, you change the maximum aperture available to you. You will see this in lens descriptions like so, Canon RF 100-500mm f/4.6-7.1L IS USM. With this example the lens has a maximum aperture of 4.6 at 100mm and decreases to a maximum aperture of 7.1 at 500mm.

Prime lenses typically have a faster maximum aperture than zoom lenses which makes them ideal when working in low light and blurring out the background in your photos.

One more aspect of the prime vs zoom debate has been image quality. Historically prime lenses offered the best results when it came to image quality. This isn’t the case anymore. A well-built zoom lens such as the Canon RF 24-70mm f/2.8 IS USM will produce amazing results across its whole range of focal lengths. Combined with a little lens correction in post processing and you won’t even be able to tell a difference between it and a prime lens when you are looking at image quality.

There are other lens types out there, but they aren’t that important when learning boudoir photography in my opinion.

Other Lens Features

There are other lens features you might find useful in certain circumstances. A lens with built in stabilization will help you get sharper images at lower shutter speeds and produce smoother videos. Different lens motor types affect the way a lens will acquire focus which is useful for video work or if you are photographing a fast-moving subject. If you are going to use your lens out in extreme weather conditions you may want to look into lenses with weather sealing.

Glass! Glass! Glass!

If you have to choose between spending money on a camera body or a good lens, always choose the lens. A good lens on a decent camera body will give you better results than a cheap lens on a high-end camera body. This is one of the reasons I went with the camera and lens combination that I did when I was looking to upgrade my gear a few years ago.

Quality glass also holds its value really well over the long haul. So, if you ever need to sell a lens you will be able to get top dollar for it.

Final Thoughts

Whew! That was a lot. I hope you now have a better understanding of lenses and lens terminology. It took me awhile to get all this down when I was first learning so don’t be worried if it takes you awhile to figure it all out. For the next article on Photography Basics click the link below.

One last thing. If you are enjoying this blog and wish to support the work I do here, consider using the Buy me a Coffee button at the bottom of the page to make a one time donation to show your appreciation.

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