Understanding Camera Lenses :: Digital Photo Secrets

Understanding Camera Lenses

by David Peterson 6 comments

Intermediate "One of the many revelations that photographers have is discovering the difference between letting your camera decide how to do something, and telling your camera what to do." - James Brandon

I love that quote by James Brandon because it speaks to all that I do to inform photographers on how to use their camera to its fullest. Naturally, part of your camera is the lens you use with it. This post is dedicated to helping you determine which lenses are best for you so that you can control the outcome of your images.

Technological Differences

What may surprise you is that the size lens that worked for your old 35 mm film camera may not work as well for your DSLR. Therefore, choosing lenses for a DSLR is more complicated than when you bought lenses for a 35mm film camera. The reason why is because a DLSR sensor is generally smaller than the frame of 35mm film. Lenses, at the same time, are still labelled for 35mm film cameras, unless you buy a digital-specific lens.

Picking out a lens for a 35mm film camera was simple because 35mm lenses capture images as you see them. A short lens, such as a 20mm, 24mm, or a 28mm, are focal lengths for wide-angle lenses that take wide-angle photos. Telephoto lenses have focal lengths greater than 35mm and give you the ability to capture close-up images without having to be that close to your subject.

A term called "field of view crop" means that a DSLR's sensor is smaller than a 35mm film frame. Though they're more expensive than most hobbyists might want to spend, there are "full-frame" DSLRs that have the same size sensors as a 35mm frame. As such, they aren't impacted by field of view crop.

Field of view crop is also referred to as the multiplication factor or focal length multiplier. Common values for field of view crop range from 1.3 to 2. To determine the amount of crop you're experiencing on a non-full-frame camera (like a digital camera), you would multiply a lens' focal length by the multiplier to determine its 35mm equivalent.

As a basic example, if your camera sensor's field of view crop is 1.5 (which it is for a lot of digital cameras), a film lens marked as 50mm will actually give you a focal length of 75mm.

If you can afford a full-frame camera, the lenses you buy will give you more realistic and higher quality results.

Choices - Zoom, Telephoto, Wide-Angle

There are so many lens choices out there, which can make it overwhelming to try and figure out which ones are right for your photography needs. So, let's take a look at some options.

Zoom versus Telephoto: To start with, let's get some terminology cleared up. A lot of beginner photographers confuse zoom and telephoto lenses. Don't let this confuse you because zoom lenses and telephoto lenses are not the same. Simply put, zoom lenses can be any focal length. The key is that they have a barrel that extends to change the focal length. On the other hand, a telephoto lens has a longer than normal focal length. A telephoto lens can be a zoom lens, but not all zoom lenses are telephoto. You'll find both wide-angle and telephoto zoom lenses.

Now that that's cleared up, this will make more sense: there are two different types of lenses: fixed-length and zoom. The common debate is which one is better? Well, that depends. A zoom lens will give you more versatility and is less expensive than buying multiple fixed lenses to meet the focal lengths that a zoom lens has. However, the debate is whether or not a fixed lens produces sharper images.

Standard Zoom Lens: When you're starting out, I recommend that you use a standard ranged zoom lens that gives you a range of about 28mm-135mm. This gives you good versatility to use a telephoto to get closer, but you could be limited on some wide-angle shots.

Wide-Angle: If you tend to shoot a lot of landscapes, a good second lens to invest in is a wide-angle lens. Wide-angle lenses capture wider views, allowing you to fit very large subjects into the frame (without needing to move a long way away). They are perfect for not only landscape, but also architectural photography or even just a big group shot. They run in 20mm, 24mm, and 28mm lenses. A focal length shorter than 16mm will give you the fisheye effect, which distorts the image, causing it to curve around the edges for a more artistic approach.

Fisheye lens causes the horizon to be curved


F-numbers refer to aperture, which determines how wide the aperture opens or doesn't open. A deciding factor for a lot of photographers is the f-stop range a lens has. Aperture affects the amount of light let in, which creates the depth of field and impacts shutter speeds and field of view. So ideally, the smaller the f-stop capability, the better because you have more flexibility.

You'll see lenses with minimum f-stops of f/2.8-4, for example. A lens with large f-number gives you a wider depth of field and a smaller f-stop gives you a shallow depth of field, which is great for portraits.

Ideally, the lenses you invest in should have a wide range when it comes to f-numbers. It is more important to professional photographers to have lenses with a smaller f-number (for example 1/1.4 as opposed to 1/2.8) to accommodate the shallower depth of field range. The smallest f-number is often referred to as the lens' speed, and that's because it will dictate the fastest shutter speed you can get with the lens.

Most people think this post is Interesting. What do you think?


  1. farruk says:

    Dear sir,
    First of all i want to thank you for such a wonderful website. i learned lot from here.
    I want to start photography. i just want to take photo for friends and family. and then they share this in social media . and everyone asked them who toked this photo? very nice. a good compliment for me.
    so, which SLR i choose for this kind of photography? Could you please suggest me which camera and lenses should i buy?
    please please.....
    best regards

    • David Peterson says:


      You honestly don't need an SLR camera to take shots where everyone asks 'who took the photo?'. It's more about what you place in front of the lens rather than the type of camera and lens that you have.

      This article should help you in creating a 'work of art' rather than just a snapshot: http://www.digital-photo-secrets.com/tip/4904/beyond-snapshots/

      I hope that helps.


  2. Susan Sheppard says:

    Thanks David. Your info was very helpful.

  3. Susan Sheppard says:

    I still find it frustrating to operate my Nikon 3300 cam since Feb. I try using the telephoto and wide angle and they come out with dark edges so I lose my full image when I photo edit them. Now the zoom is next to nothing and I want to photograph birds in trees and items far away but have no clue what size zoom I need for this shooting. Can you inform me? Thanks

  4. kevin Fleming says:

    At Last... Someone refering to 35 mm As most of us have some interest in the past ,,although total digitalnow it makes sence to remember Capt Cook had a sailing boat (the endeavour) he did not use a a space ship !,

  5. Elisabeth says:

    could you write an article about how to set up/use the Canon EX 600 Speedlite for weddings? Thanks

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