In this guide we will go over what all the specifications mean to help you choose an appropriate optic for you!
We will be covering this from a photographers point of view and only touching lightly on each subject. Most photographers won't require this guide. It's aimed at new users who only have the basic kit lens and are looking for something better suited to what they shoot.
The camera lens is the most important part of your gear
It's what's really taking the photo. The camera records what the lens sees. Most of your image quality is coming from your lens, not your camera body.
Two lenses that seem superficially similar may vary greatly in price. For example the Canon EF 50mm f/1.2L USM retails at over 10x the price of Canon EF 50mm f/1.8 STM. Despite the similar focal length the former lens offers far superior optics resulting in less flare and better colour and contrast than similar lens, in addition to other features like weather-proofing and an 8-blade circular aperture for excellent out-of-focus blur. With the extra cost also comes increased size and weight.
We will break it down further below.
Both of these lens compete against each other however as you can see, the sigma renders color and tones differently. It pays to look at lots of sample images before you choose. Things like colour and tone are really impossible to work out just looking at specifications.
For this example I'll use the Nikon Nikkor AF-S 24-85mm F3.5-4.5G ED VR FX
This is the brand that makes the lens. A Nikon lens will only fit onto Nikon bodies, the same applies to Canon. Tamron and Sigma are 3rd party manufacturers and will produce versions of lens for all kinds of different cameras. Most camera manufacturers only make lenses for their own systems.
Since many of these camera brands are very old, they still label lenses with things like Nikkor or Fujinon. You can generally ignore this. As long as your mount is correct it's going to work.
This is the auto focus system. They come in lots of different types from Canon's USM to Nikon's new AF-P system (not all nikon cameras work with AF-P). If your seeing something like this in the title, it has auto focus. Some manufacturers don't list this anymore in the title so if unsure, read the full specifications of your lens or ask us.
This is the focal length and is really important. Focal length is going to determine how wide or telephoto your lens is going to be.
The lower the number, the wider it is, the higher, the more "zoomed" it is.
If you see a hyphen ("-") in the title of a lens, it zooms. This Nikon lens has a range from 24-85mm, great for landscape and portraits. You can use any focal length within the 24-85mm range. Not all lenses zoom. Prime lenses are always at one focal length. The advantage of these is that they can operate at faster shutter speeds than zoom lenses and therefore are great for sports related photography.
This is the aperture. The f stands for focal length and the number following is a fraction of the focal length. This is why often - but not always in this case - the focal length is denoted with 'f/' e.g. f/1.2.
"...the lens aperture is usually specified as an f-number, the ratio of focal length to effective aperture diameter. A lens typically has a set of marked "f-stops" that the f-number can be set to. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor."
Aperture controls the amount of light reaching the camera sensor. The bigger the "hole" the more light hitting the sensor. It is also influences depth of field to a degree. Higher numbers make the aperture rings go smaller, keeping more of the scene in focus.
Note that if there is a hyphen ("-") in the aperture, it makes it changes as it zooms. It gets darker as the focal goes up. It's possible to buy lenses now that don't change aperture as the focal changes though they are physically larger and more expensive. If you're into video it's very helpful.
This is the type of glass used. Not all brands will mention it.
This is also quite important for longer focal lengths. It stands for vibration reduction and helps counter hand shake allowing for a sharp result with a slower shutter speed. If you only use your lens on a tripod, you don't need this. Also, some cameras now like Olympus's mirrorless models have vibration reduction built into the camera, meaning that every lens attached will have some form of stabilisation.
Other brands use a different mark to display if the lens has vibration reduction. Tamron uses VC and Canon uses IS.
FX in Nikon's range stands for Full Frame. DSLR cameras typically come in two different sensor sizes. Full frame, which is the same as a 35mm film strip or crop.
When a lens mentions it's 24-85mm, it's saying that it's a 24-85mm on a full frame 35mm sensor. If you have a cheaper camera you would have a crop and would need to think about the crop factor.
Canon's APS-C sensors have a crop of 1.6x, Nikon's crop is 1.5x a roundabout.
A couple of things that crop does not change:
Crop factor does NOT affect a lens’s focal length. Crop factor does NOT affect a lens’s aperture.
It does change your field of view though, a cropped sensor sees less then a full frame using the same focal length lens. For example a 50mm lens on a Nikon crop sensor body would have the field of view of a 75mm lens, quite a bit narrower.
And that's just the basics
A good lens doesn't come cheap, before purchasing a lens always read reviews and look for sample images from that lens.
If you have any questions about camera lenses please feel free to contact us