Types of Lenses

When I first started to get into photography, the first thing that completely baffled me, was the numbers. 80mm this, and 4.5 that, what on earth was all this stuff? When trying to work out what camera I wanted, I was at a complete loss, and instead resorted to one that I knew others had, or had seen photos taken by it.

It still didn’t get any better when I moved into SLR photography, and I had to start buying separate lenses! It was time to learn what the numbers really were.

Some photographers quite happily go through their entire lives not really know what the numbers mean from a technical perspective, and just know what the numbers mean using their own system. This is perfectly alright in my book… if you know that 100mm is more “zoomed in” than 24mm, then that’s good enough. I personally like to understand it a bit more and I will be going into some but not all of that technical detail in this guide.

The Numbers

Let’s start with the matter of numbers, and get that out of the way.

85mmI’ll take an example lens from my collection to start with. I call it my “85 mill” as would most photographers, and you’ll see why. Its official name is the Canon EF 85mm f/1.2L II USM Lens. I’ll break that down into its parts:

Canon | EF | 85mm | f/1.2 | L II USM

Canon

Obviously this is the manufacturer of the lens.

EF

This is the type of mount. The mount is the part that connects the lens to the camera. On Canon DSLR cameras, there are 2 mounts: EF and EF-S. If your camera supports EF-S lenses it also supports EF, but if you’ve got a full-frame camera for example, which only supports EF lenses, you cant use an EF-S lens on it. Other camera manufacturers have different mount systems, such as the F-mount on Nikons and E-mount on Sonys. Some lens manufacturers like Sigma, make the same lens, for different mounts, so be careful you’re getting the right lens for your camera.

85mm

This is the focal length of the lens. The non technical way to explain this, is how “zoomed in” the lens is. The higher the number, the more “zoom” you’ll experience.

Anyone who already knows technically what focal length is will probably be cringing that description though. A more technical way (but still brushing over a lot of the detail) of explaining it, is that it’s the distance, in millimetres (hence the mm and the “mill” nickname we give each lens) between the centre point of the inner lens pieces, and the camera sensor. The longer that distance, the more magnified the light is as it passes through the lens to the sensor, and the shorter the distance, the more of a wider amount of the “scene” will be captured. Hopefully this really basic diagram helps:

focal length

f/1.2

This is the lowest f/stop the lens will go down to. the f/stop is the measurement of the aperture size relative to the lens’s focal length. To understand this more, head over to my article on Aperture here. But essentially, the lower the f-number in the lens name, the better the lens will be at helping out in low-light situations.

L II USM

These are pretty much Canon only things, the L indicates that this lens is from their “Luxury” range, i.e. designed for professionals and of higher quality than non-L lenses.

The II indicates that this is the 2nd version of this lens, there was an original version which they no longer make.

The USM indicates that this lens has an UltraSonic Motor inside it to speed up the focusing.

You’ll find other lenses have other letters at the end, indicating specific technology being used, such as lenses that end with IS, which indicates they have Image Stabilisation technology inside them.

 

Now we’ve got all of that out the way, lets look at some general terms used to group lenses. I’ll explain what these names typically mean:

Zoom Lenses

When a lens is referred to as a Zoom lens, this simply means that the focal length (described earlier) is adjustable. For example if you have a 75-300mm lens, this means you can adjust the focal length from 75mm through to 300mm, allowing you to either take either relatively normal magnified photographs, or zoom right in for a big closeup using the 300mm setting. Great lenses for someone who’s going to be shooting a range of different types of photos and doesn’t want to keep changing lenses. The downside is that zoom lenses often sacrifice a bit of quality, and don’t go down to the very low f/stops.  I don’t use zoom lenses, but that’s a personal preference.

It doesn't come much wider than this. Taken using my 15mm Fisheye wide-angle lens

It doesn’t come much wider than this. Taken using my 15mm Fisheye wide-angle lens

Prime or Fixed Focal Length Lenses

These are my lenses of choice. If you have an 85mm prime lens, it’s always going to be an 85mm lens, you can’t adjust the focal length, so if you need to magnify what you’re looking at, you’ll need to use your legs, and walk towards it. Prime lenses often have superior image quality and can go down to very low f/stops, often less than f/2.0

Wide Angle Lenses

These are the lenses with the short focal lengths. Some say that 35mm and below are classed as wide angle. With a low focal length, you get more of the scene in the image, hence the name. The downside is often image distortion, as the scene is stretched across the image. Super-wide angle lenses often have extreme distortion/stretching that is very noticeable.

Telephoto Lenses in use by the press

Telephoto Lenses in use by the press

Telephoto Lenses

These are simply lenses with really high focal lengths, usually 200mm and up. They’re often used by sports or wildlife photographers. Canon L glass telephoto lenses are white. You’ve probably seen sports photographers with those big white lenses on before.

A macro shot of a ladybird bug

A macro shot of a ladybird bug

Macro Lenses

Macro photography or the more cool sounding word that no one actually uses: Macography, is the art of photographing things very close up so that the final photograph shows the subject in at least life-size, or more often, larger than life-size. A typical example is a picture that shows a tiny insect in very clear and large detail, another might be the lovely enlarged photographs of jewelry in a jewelers shop window.

So, naturally you can expect that a Macro lense lends itself to this form of photography better than any other type. It does this by having both a long lens barrel and a very short focussing distance. That basically results in the subject being magnified and very close to the end of the lens to ensure as much of the image can be used to frame the subject.

Tilt and Shift

This is a weird one. Chances are you’ve seen photos taken using Tilt and Shift lenses, but you may not have had any idea. The basic principle is that parts of the lens can be moved, relative to the camera itself. You can tilt parts of it, and shift parts of it, hence the name. This then produces some interesting effects on the image, such as correcting perspective. Architectural photographers often use Tilt and Shift lenses for this purpose, enabling them to remove most or all of the perspective from the image.

Another effect can be to impact how much of a wide scene is in focus. When adjusted in a certain way a Tilt and Shift lens can be used to increase sharpness across a whole scene by impacting the depth of field, but similarly, it can be adjusted to give the effect of a very shallow depth of field too. We normally only see shallow depth of fields in photographs of things reasonably close to the camera, so when we see a shallow depth of field on a large scene such as a landscape photograph, the brain is often tricked into thinking what you’re actually seeing is a miniture recreation of a scene.

Full Frame and Cropped Sensors

The terms Full Frame and Cropped actually refer to camera design rather than the lens itself, however what type of sensor you have will have an effect on the way some lenses perform. This particular subject really only applies to DSLR cameras and lenses.

I touched on lens mounts earlier, and mentioned that with Canon lenses there’s EF and EF-S mounts available. The reason for the different mount types, is because Canon started to produce lenses specifically for cropped sensor cameras.

Cropped sensor simply means that the sensor chip inside the camera is smaller than the full 35mm frame size that you’ll get in a Full Frame camera. The term Cropped is used because the lens still projects the same sized image onto the sensor area of the camera, therefore with a smaller chip, not all of the image is captured, effectively cropping what the lens “saw”.

If I put my 85mm lens onto my full frame camera, I will get the full image produced using the 85mm focal length. If however I put the lens onto a cropped camera, for example a Canon EOS 600D camera has a smaller 22.3mm sensor chip size, then the image taken will appear more “zoomed” in than on the full frame. This is called the crop factor, and on the 600D the crop factor is 1.6. A quick bit of simple maths tells you that 85mm x 1.6 gives you 136mm, therefore on a camera with a 1.6 crop factor, an 85mm lens is actually a 136mm lens.

This is good some of the time (getting more zoom out of your telephoto lens) and bad other times (your wide lenses are not as wide as they’re supposed to be). So Canon brought out some lenses that are designed to work with cropped sensors. Some of them do this by having parts of the lens extend into the camera body, effectively shifting the center point of the lens and therefore shortening the focal length. The problem with that design change, is that full frame cameras aren’t designed to have “bits” inside them, and potentially things such as the camera mirror hitting the lens part, could occur, so Canon had to make a new lens mount that would hopefully prevent someone trying to fit one of these cropped-specific lenses to a camera not designed to handle it. Thus the EF-S mount was invented.

Other lens and camera manufacturers have the same sort of systems, with different mount and lens names. Some lenses designed for cropped cameras do actually fit and work on full frame cameras, but usually in those cases the result is a black border around the image, as not all of the full frame sensor is used by the lens.


 

So thats it, the basic types of lenses out there. I have one good rule I stick to when buying gear:

A Camera will date, but a good bit of glass will always be a good bit of glass.

Basically, invest in lenses more than you do your cameras, as you’ll probably replace your camera in a couple of years, but you’ll carry on using them great lenses forever.

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