Welcome back to our series on backpacking photography. Today’s article is dedicated to looking at lenses for both interchangeable lens cameras as well as those on compact cameras. Let’s just jump right in…
How Does a Camera Lens Work?
In a nutshell, the lens gathers the light entering it from all angles, focuses it on an infinitely tiny point (the focal point), then projects it onto the camera sensor, or film for you geezers who are sticking to your guns. The inside of the modern lens consists of multiple glass elements, each performing a specific job. Some correct for distortion, others ensure that different colors of light are focused correctly despite differences in their wavelengths. There is no perfect lens, but the difference between a quality lens and a mediocre one can be huge. Higher quality lenses generally contain more and higher-quality glass elements, resulting in a better rendered image, and a bigger, heavier lens. Below is a cross sectional view of the Canon 24-105mm zoom lens, all 18 glass elements can be seen inside.
So, What Makes a “Good” Lens?”
There are so many criteria that can be used to analyze a lens; many of those criteria are not subtle and the use of technical papers and graphs is needed to interpret them (yay!… boring), while others are purely subjective such as whether colors are rendered warm or cool. To make quick work of analyzing a lens there are a few key things to consider.
- How does the lens perform at it’s wide open aperture? You’re being critical of sharpness and vignetting.
- How does the lens perform in high contrast scenes? You’re being critical of chromatic abberation (green and red junk around high contrast edges).
- How does the lens handle sun flare? You’re being critical of how easily the lens will flare in bright light situations.
For the average user these criteria are probably sufficient to tell whether the lens is up to snuff or not. The latter two are especially important for backpackers or anyone who’s bound to take photographs outside where high contrast scenes and bright light is the norm.
What Focal Length Do I Need?
The focal length (or range or focal lengths) of a lens determines how wide or, alternatively, how ‘zoomed in’ the view will be. The smaller the number, the wider the view. For compact cameras focal lengths are almost always listed as “equivalent”. This is just a reference to what the field of view looks like compared to a 35mm camera with a lens of the “equivalent” focal length. In reality the sensor on your compact camera is very small and the actual focal length of the lens may only be a few mm, but who can relate to that?? It’s easier just to say it has a 24mm equivalent which a lot of people will recognize as being a wide angle. The image of the Nikon CoolPix below shows the 4-45mm lens, which the specs reveal is equivalent to 25-250mm. The maximum aperture value is also shown as f3.2-5.8 …not a very fast lens (more on this later) although it does have a nice zoom range.
Moving on… for shooting landscapes and scenery it’s nice to have a wide angle of view around 24mm. Most compact cameras and zoom lenses offer a zoom range of 5-7 times whatever the widest focal length is, for example 24-135mm. It’s not enough to zoom in on distant animals, but nice for taking portraits and other shots where you want to isolate the subject a little better. Some models offer 10x zoom (or more) but they tend to be heavier, slower, and not as optically pristine when it comes to the lens. If you’re planning to dedicate energy and money to becoming a wildlife photographer an SLR with big telephoto lenses (400-800mm) will bring those far away subjects right up close… but that’s a whole other ball of wax.
Is Maximum Aperture Important?
For landscapes and scenery, not so much. For general use and portraits – yes. The opening in the lens is the aperture and is set by adjusting the f-stop value (when using auto-exposure modes the camera will adjust the aperture automatically). The smaller the number, the larger the opening. In the case of most, if not all, compact cameras the lens will have a variable maximum aperture; you might even see it printed on the end of the lens, something like “f2.8-5.6”. So, as the lens is zoomed in our out the maximum aperture will be restricted to a value somewhere in that range. In our example f2.8 is the maximum aperture at the wide end and the 5.6 at the telephoto end. Focal lengths in between will have max apertures that fall somewhere in the range. But why does this matter?
The aperture affects two important optical qualities: A) the shutter speed you can use, and B) the amount of background blur you can achieve. If you’re in a situation where the light is not abundant and you zoom in to take a photo you may find that your shutter speed is too slow because the aperture is too small. The result – the photo turns out blurry. Conversely, say you’re taking a photo of someone or something that you want to isolate with an out of focus background. Wider apertures will blur the background details out, so f5.6 may not work in this case. For the same reason this is why I say that the maximum aperture isn’t critical for landscape work where having as much detail as possible is the goal. In that case you don’t want to be shooting with the lens wide open. Most lenses perform their best between f5.6-f8.0 which you may find very suitable for landscapes.
Sometimes the term “fast” is used to describe a lens. This usually refers to lenses that have a maximum aperture of f2.8 or below. A full “stop” on the aperture means the lens will produce the same exposure with half the light of the previous stop (“stop” is sort of a way of talking about exposure in a generic sense). The aperture f2.8 is 1 stop faster than f4.0 and 2 stops faster than f5.6. So for the same exposure the shutter speed can be doubled by opening the aperture from 4.0 to 2.8 – or it can be quadrupled by opening the aperture from f5.6 to f2.8! Follow along here… f5.6 to f4.0 doubles the speed, f4.0 to f2.8 doubles it again, net result 4x as fast. If it’s dark around and you’re shooting hand held with a shutter speed of 1/30th of a second at f5.6 you’re probably going to have some camera shake. Open the aperture up to f2.8 and suddenly your shutter speed is 1/120 second! Score! Of course you don’t have to increase shutter speed, you can instead or in combination, decrease your ISO setting at the wider aperture. Since you have more light to work with, use a lower ISO and get a cleaner shot. It’s all about creative balance. One last thing you might be wondering: “why are the aperture settings these funky numbers??”… it’s because the area of a circle varies with the square of the radius. As the aperture blades make a smaller circle opening for light to pass through the area controls the quantity of light, thus the aperture setting doesn’t just double of halve. An easy way to remember stops by aperture is to remember 2 numbers: 1.0 and 1.4. Each full stop is an increment of those numbers starting at f1.0, and alternating…. f1.0, f1.4, f2.0, f2.8, f4.0, f5.6 …. and on and on…. blah blah blah. So now you know why some lenses are fast. A small difference in the maximum aperture has a big impact in the way the lens performs.
Users of compact cameras
You will find that the max aperture is usually f2.8 or f3.5. A few cameras offer f2.0 which is nice to see. For general use it’s nice to have a lens that can open up as wide as possible; there are always occasions when you can use the extra light, or want to limit the depth of focus. As for the rest of this article, you may want to skip to the conclusion. The next couple of sections pertain to interchangeable lens users.
Users of interchangeable lens cameras
The next couple of sections really pertain to you. The choices you’ll make in lenses are going to affect the weight of your pack and your wallet!
Are Lenses with Fixed Aperture Better?
Yes! Well, it depends. Ok, so it really really depends on the lens and what you’re comparing it against. But I digress… yes they’re better. Why? Because they are more expensive! You’re thinking “that doesn’t prove anything”, and you’re right, but the price is not what makes them better. Making a fixed aperture lens requires a more complex lens design with larger glass elements so naturally the lens is going to cost more to make, and with retail mark up is going to cost a lot more right out of the gate. It makes sense for manufacturers to put these types of lenses into their premium lens lineup, so typically the entire lens is built better. Typically fixed aperture lenses come in two flavors: f4.0 and f2.8… the latter is much larger and more expensive than the former. Do you need a fixed aperture lens? Probably not, but it can be nice. It doesn’t matter what focal length you’re working at, you can control the aperture so you can control the shutter speed and the background blur. Owning control over all of these things is more typical of the SLR user, and it’s ok because you won’t find fixed aperture lenses in compact cameras.
In the image above the Canon 70-300mm (left) has a variable aperture, and even though it’s got 100mm more reach than either of the other two lenses, it’s quite a bit smaller and lighter! The 70-200 f4.0 in the middle is getting a little beefier, and the f2.8 version is a brick. All that glass can be heavy to carry around.
What’s Up With Prime Lenses?
Prime lenses, or simply “primes”, are lenses that have a fixed aperture and a fixed focal length. The lens does not zoom in or zoom out… instead zooming is done with your feet! I like to make “zoom zoom” sounds when I move around to zoom. All the strange looks you’ll get make for good candid portraits! There are four reasons why you might want to use prime lenses…
- Compact Size: Since there are no moving components inside the lens to support zooming, the design is simple and the lenses can be fairly small.
- Image Quality: Primes are the kings of image quality due to their simplified design and typical use of high quality elements inside.
- Speed: Many prime lenses have a maximum aperture of f1.4 – f2.0 allowing them to gather lots of light and utilize fast shutter speeds.
- Cost: Prime lenses are always less expensive than their zooming counterpart… but you’ll find yourself owning more of them probably.
It’s common for photographers to keep at least one “normal length” (50-85mm) prime in their kit for portraits and casual use where having a wide-aperture (a.k.a. “fast”) lens is desirable. Some people (such as the me) exclusively use primes. I just find that they suit my style, but the real trouble with them is they’re addictive! The image quality and speed makes them a ton of fun to work with. Working with fixed focal lengths has it’s pros and cons. On the positive side, it becomes easy to learn the character of each lens since each has only one focal length. Zoom lenses on the other hand have multiple personalities depending on the focal length you’re working at. To be fair though, some people dislike primes due to lack of convenience; it’s definitely a trade off. The size/weight advantage is real though. Check out this comparions between the
18-55mm 18-200mm zoom lens and the 16mm prime lens on this Sony NEX-5.
In choosing a compact camera pay attention to the lens, not just the camera features. See if you can find a lens with a max aperture less than f2.8 on the small end and no more than 5.6 on the other end of the range. Keep in mind that the super zooming models will either give up size or image quality in order to provide the extra zoom range. Do a little extra homework and try to find some reviews that talk about other aspects of the lens such as chromatic abberation, fringing, and flare. In the world of compacts lenses are small but not equal; choose carefully.
When it comes to interchangeable lens cameras, think carefully about how you’ll use it on the trail as well as around home. You probably don’t need a fixed f2.8 zoom lens, and you certainly don’t want to carry one in your backpack. Consider f4.0 zooms instead, or even the option of a lightweight variable aperture zoom; even if it’s just for your hiking trips. If you want to try a prime lens before deciding to buy one, you can rent – or simply treat your zoom lens as a prime and leave it set at one focal length your entire trip. At least this will give you an idea of how working with a single focal length feels. Interchangeable lens cameras provide a lot of flexibility, but a common mistake is to acquire lenses to try and cover every focal length. Having some gaps (or overlaps) in your arsenal is hardly the end of the world; instead put some thought into building a kit that will meet your needs in an efficient way. A kit consisting of only one zoom and one fast prime can be a very light and versatile package. Lastly, remember – Good glass is forever, cameras come and go.
Well, I hope you’ve enjoyed the series thus far. The next few articles will be written by our guest authors and are dedicated to actually taking some photos! Yay… finally something interesting ;)
Hike It. Like It.