What's A Fast Lens, Do I Need One?
Black and white portrait created with a fast lens and window light.
Buying a fast lens is a big decision. But, with the knowledge I’m going to share, your photos can improve dramatically.
A fast lens has a particularly wide maximum aperture which can let more light onto the sensor or film than a lens with a physically narrower maximum aperture. With a fast lens you can produce exceptionally shallow depth of field and sharp photos, under low light conditions, without a tripod.
What Is A Fast Lens?
Simply put a fast lens has the potential to allow significantly more light through to a digital camera’s sensor than a more conventional lens, whether it be a fixed or zoom lens.
What Are The Advantages Of A Fast Lens?
Now that we’re clear about a fast lens definition let’s check out the advantages a fast lens offers the photographer.
The use of shallow depth of field to visually separate the primary subject, from potentially competing elements within the frame, is one of the defining attributes associated with professional portrait photography.
Fast lenses have the capacity to produce exceptionally shallow DOF and, therefore, are an essential piece of kit for many professional wedding and portrait photographers.
Documentary photographers and photojournalists also favor fast glass given the low light conditions they often find themselves working under.
Take a look at this picture of a young man sitting on a staircase in a pub in Mildura, a region city along the Murray River in Australia.
I made the photo with a fast Canon 24mm f/1.4 lens at an aperture of f/2.8. The wide angle focal length allowed me to work up close and still document the surroundings which is important when creating an environmental portrait.
Notice how this combination of light, lens, aperture and camera-to-subject distance has enable me to record the scene in such a way that emphasizes the subject and visually separates them from the surroundings.
It’s worth noting that the quality of light is often most beautiful under low light conditions. Some examples worth noting include the following:
Dawn
Sunrise
Sunset
Dusk and Twilight
Cities at night
In addition to reducing the chance of subject movement and camera shake a fast lens offers the photographer the opportunity to make use of the soft, warm light at the edges of the day as well as the often evocative nature of street and interior lighting.
Lens Apertures: f Numbers Compared
Just as the camera's shutter speed determines the amount of time, usually in fractions of a second, that light is allowed to reach the sensor or film it is the aperture that determines how much light the lens allows through.
In photography speak an italics f is used to define a particular aperture (e.g., f/4).
An aperture of, for example, f/22 is referred to as a narrow aperture as it's relatively small and lets very little light through.
Conversely f/2 is a relatively wide aperture that lets significantly more light through onto the digital sensor or film.
The vast majority of lenses available today offer the ability to set one of numerous apertures from, for example, f/4 to f/16. Those apertures provide opportunities for great photos under a range of conditions.
However, a fast lens with a maximum aperture of f/2 or wider is where the fun really begins.
An aperture of f/2 provides the ability to let two stops (i.e., four times) more light through than would be the case with a common zoom lens with a maximum aperture of f/4.
Both lenses have an aperture of f/4, but only the f/2 lens has the ability to open the aperture wider than f/4. In this case to f/2.8 and, beyond that, to f/2.
I hope the rather basic illustration above helps make sense of these numbers. Lenses with apertures greater (i.e., physically wider) than f/1.4 are rare. The same is true for apertures smaller (i.e., physically narrower) than f/32.
The full list of apertures from f/1.4 to f/32 are as follows.
f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32
The distance between each of those apertures, in either direction, is referred to as a stop. Setting the aperture in between any two of these marked aperture points is often done in third or half stop increments.
Fast lens aperture of f/2 was employed to photograph these two horses.
Do Photographers Really Need Fast Lenses?
The above image of the two horses in rural Australia was made with a Canon 85mm f/1.2 lens at an aperture of f/2.
That's a physically wide aperture which, in addition to the short camera-to-subject distance, produced the very shallow depth of field that contributes to the unique look and feel of the image.
The horses are standing quite close to each other, but by critically focusing my camera’s lens on the eye of the closest horse and employing an aperture of f/2 I was able to render the more distant horse almost completely out of focus.
This technique works brilliantly whenever there’s potentially competing subjects within the frame and you want to draw attention to the primary focal point. Examples include the following:
Bride and bridesmaids
Placing attention upon a single flower in a bed of flowers
Close up baby portrait where attention is drawn to the eye closest to the camera
If you’re interested in making these kinds of photos you’ll find my post titled Selective Focus and Depth Of Field to be a great resource.
It’s important to understand that, in addition to being able to gather more light, fast lenses are generally of a higher quality than lenses with more modest maximum apertures.
That means fast lenses are relatively expensive, which is why it’s important to think carefully about whether the kind of images that are most suited to fast lens photography are the kind of photos you want to make.
Generally speaking higher quality lenses are more physically robust and offer superior image quality, particularly in relation to sharpness, color rendition and relatively even illumination, edge to edge, across the image.
The best quality lenses, whether fixed (i.e., prime) or zoom lenses, will likely be made of glass and metal, rather than plastic and plastic, and may incorporate some level of weather resistant and/or dust seals.
Fast lens highlights details of a journal on the Polly Woodside, Melbourne.
Fast Lenses For Canon Cameras
There are a number of fast lens options available for Canon cameras.
For a full frame Canon DSLR camera I’d consider the following options:
Canon EF 24mm f/1.4L II USM Lens
Canon EF 16-35mm f/2.8L III USM Lens
Canon EF 16mm f/1.4 L II USM Lens
Canon EF 50mm f/1.8 STM Lens
Canon EF 50mm f/1.4 USM Lens
Canon EF 85mm f/1.4 IS USM Lens
Sigma make a number of high quality fast lenses that provide a decent alternative to Canon glass. Here’s a few Sigma fast lenses worth exploring.
Sigma 14-24mm f/2.8 DG HSM Art Lens
Sigma 35mm f/1.4 DG HSM Art Lens
Sigma 50mm f/1.4 DG HSM Art Lens
Fast Lenses For Canon APS-C Cameras
The Canon APS-C cameras have one particularly interesting fast lens in their range that I think is worth a look.
Canon EF-S 24mm f/2.8 STM pancake Lens
Canon APS-C camera also have a number of interesting options made by a wide variety of manufacturers, including the following.
Tokina Opera 50mm f/1.4 FF Lens
Fast Lenses For Canon Mirrorless Cameras
When it comes to a Canon Mirrorless camera you might consider one of these lenses.
Canon RF 15-35 mm f/2.8L IS USM Lens
Canon RF 85mm f/1.2 USM Lens
Fast Lens For Nikon Cameras
Like Canon, Nikon manufacture a large range of lenses. The best of their fast lens options include the following:
Nikkor AF-S 24mm f/1.8G ED FX Lens
Nikkor AF-S 35mm f/1.8G ED FX Lens
Nikkor AF 50mm f/1.4D FX Lens
Nikkor AF-S 85mm f/1.4G Lens
As far as a Nikon lens for their APS-C type cameras I’d say the pick of the crop, when it comes to fast lenses, would be the following:
Nikkor AF-S DX 35mm f/1.8G Lens
Fast Lens For Sony Cameras
These days Sony is my camera of choice. I switched over to Sony full frame mirrorless cameras a number of years ago.
If you own a Sony a7, a7R or a7S some excellent fast lens options await you. Here’s a few worth considering:
Sony FE 24mm f/1.4 GM Lens
Distagon T* FE 35mm f/1.4 ZA Lens
Sony FE 16-35mm f/2.8 GM Lens
Sony FE 16-35mm f/2.8 GM Lens
Sony FE 85mm f/1.4 GM Lens
Sony also have a range of APS-C size sensor cameras. Of the fast lenses designed to fit those cameras these are the ones I find the most interesting:
Sonnar T* E 24mm f/1.8 ZA Lens
Sony E 16-55mm f/2.8G Lens
Sony E 16mm f/2.8 (pancake) Lens
Sony E 20mm f/2.8
What’s Best Fixed or Zoom Lenses?
Depending on the focal length it's possible to acquire a fixed (also called a prime) lens with a maximum aperture of f/1.4 for a number of wide-angle, standard and short telephoto lenses.
As a way of explanation f/1.4 allows 8 times more light to reach the sensor than f/4.
Making images at an aperture of f/1.4 has the affect of increasing the camera's shutter speed from, for example, 1/8 second up to 1/60 second, thereby minimizing the chance of blur resulting from camera and/or subject movement.
As explained previously, an aperture of f/1.4 also has the capacity of producing a substantially shallower depth of field (DOF) than would be the case with the same image made at an aperture of f/4.
Under the right circumstances really beautiful images can be produced at a physically wide aperture of around f1/4.
However photography is a game of compromise and that kind of aperture is only available on certain fixed or prime lenses.
So, while you gain the opportunity of creating extremely shallow DOF and/or making sharp photos without the use of a tripod under low light conditions, you do so without the convenience a zoom lens provides.
f/4, 65 mm focal length and a short camera-to-subject distance.
The Alternate to a Fast Fixed Lens
There’s no doubt that zoom Lenses represent convenience for the photographer. However, most zoom lenses are compromised by their light gathering capabilities.
Zoom lenses are, in effect, a variety of different focal lengths within the one lens. For example, a common kit lens will cover a range of focal lengths from wide angle to moderate telephoto.
Zoom lenses incorporate a number of individual glass elements, some of which move, in relation to each other, as the lens focal length is altered through the act of physically zooming in or out.
Some of these glass elements enhance the performance of the lens. However, the more glass present the more likely it is that the amount of light getting through to the sensor will be reduced.
This can reduce the chance of creating images with exceptionally shallow depth of field and limit opportunities to make photos, without a tripod or flash, under particularly low light conditions.
While you can increase your camera’s ISO to boost the shutter speed to a level that will allow you to hold your camera still, there’s always the chance that doing so will result in an increase in apparent noise.
As a result zoom lenses with maximum apertures wider than f/4 are expensive and relatively heavy. This is particularly true for zoom lenses that incorporate ultra wide-angle and powerful telephoto (i.e., telescopic) focal lengths.
However, all is not lost. There are three factors that determine depth of field.
Aperture selected
Lens Focal length
Camera-to-subject distance
As you can see from the black and white portrait above, by zooming and photographing from a relatively close camera-to-subject distance I was able to produce a lovely image with an acceptably shallow depth of field.
I made the image at 65mm with a Canon 24-105mm zoom on an older Canon 5D Mark II camera at the rather modest maximum aperture of f/4.
The trick then, when seeking a shallow depth of field with a more modest aperture, is to get closer to your subject. And you can do so by zooming in and/or moving closer.
It sounds so simple, but the fact is you have to know a lot to understand how the simplest solutions are often the best.
If you’d like to know more about Depth Of Field you’ll find my post titled Depth Of Field: Ultimate Guide For Photographers to be a great resource.
Christian cross and rainbow at the Lake Bolac Cemetery in Victoria, Australia.
Improve Composition With Fast Lenses
There's no doubt that a zoom lens offers a great deal of flexibility when it comes to framing an image. If your subject is too far away simply zoom in to allow them to fill more of the frame.
Likewise zooming out will allow you to fit more of the surrounding scene into your composition.
The problem is that zooming effects more than just the size of the subject within the frame. Zooming in or out changes focal length which alters perspective.
As a consequence of zooming your lens the relationship (i.e., perceived distance) between the subject and its surrounds is altered, and not always for the best.
What’s more be aware that, whenever you zoom in, less of the surrounding environment will be recorded in the image.
If you want to concentrate attention on the primary subject of your photo that’s usually the right action to take.
However, if you want to depict your subject in relation to their environment, than a different approach is required.
Take a look at this image of a Christian cross framed by a rainbow in the Lake Bolac Cemetery in Western Victoria, Australia.
It’s a great example of how to tell a story by including relevant information from the surrounding environment, while still placing attention on the primary subject or focal point within the image.
The secret is to photograph close to the primary subject with a wide angle lens.
As the name suggests a wide angle lens allows you to record a wider angle of view and, thereby, include more of the scene (left, right, above, below) in your composition.
However, the compromise is that, by including more information in the frame the wide angle lens pushes the foreground further away and also extends the perception of space between foreground, mid ground and background elements within the image.
To avoid your primary subject diminishing in power you need to move in and make your photo really close to the subject.
That’s exactly what I did in the photo of the Christian cross and rainbow which I made with my Sony a7R ii camera at 18mm with a Sony/Zeiss 16-35mm f/4 lens attached.
By moving in close the subject becomes more prominent and the wide angle focal length allows me to include the incredible rainbow and plenty of the other graves in this lovely rural cemetery.
How To Make Amazing Photos With A Fast Lens
Please remember that photography is a physical endeavor and your best photographs will often be those that were made by changing your camera's relationship to the subject.
And the best way to explore this concept is through moving around and changing the camera-to-subject distance.
By doing so you’ll likely produce far more interesting and compelling compositions than would be the case by simply zooming your lens.
The focal length of your lens will also make a difference. But don't forget to move. It costs nothing and can produce very creative results.
Likewise the lens you use can provide you with critical advantages, such as the ability to gather light and achieve incredibly shallow depth of field with a fast lens.
But, despite the lens being used, it’s how you use that lens that contributes to your ability to produce truly unique pictures.
A fast lens with a particularly wide maximum aperture is a great asset. However, whether it’s a quality fixed lens or a top level zoom, you’d be wise to get the best value from that lens by taking a more physical approach to your photography.
Get the best lens you can afford, but don’t forget to move in search of better lighting, to improve the composition and to achieve a more interesting perspective.
