One of the very first posts I wrote was about what you should consider when buying a new lens. The article was pretty shallow, however, and I’d like to delve deeper into the problem. This article will repeat some basics about lens specifications, list up a few examples of “famous lenses” and go into a couple of things you can do to verify a lens’ quality without actually testing it yourself.
Let us start by repeating a quick summary of the previous article. The lens market is a heavily contested one. Most people do not buy many lenses, and what kind of lens they buy depend on how new they are to the game, what kind of photography they want to pursue, what kind of recommendations they local photography store gives them and so on. There are roughly speaking three things to consider when looking at lenses and their specs. 1) What is the focal length/range? 2) What is the aperture size(s)? 3) Does it have any extra features like IS/VR/HSM/etc.? And finally the hidden fourth thing which is more or less a matter of taste: Is the build a solid one or does it feel like flimsy plastic in your hands?
1) Focal length and/or range
This is represented by the number followed by “mm” (millimeter) on the lens. It says something about how wide an angle is captured on the camera when attached. The smaller the mm, the wider the angles. Keep also in mind that if your camera is not a full frame camera, you will likely have to multiply the focal length by something called a crop factor. Many DSLRs have a 1.6 crop factor, while some do have 1.4 or 1.5. This is to make up for the smaller sensor.
See the picture above. Imagine you are using a 50 mm lens. The image reflected into the camera from the lens will naturally be circular because the lens is circular. The squareness of the photo is because of the squareness of the sensor. If you put the lens on a crop sensor camera, you’ll get the picture within the green border. If you put it on a full format camera you’ll get the picture in the red border. We say that the crop sensor has a crop factor which varies from camera to camera. Many have a 1.6 crop factor, which means for this example: 50mm * 1.6 crop factor = 80mm. The image captured in the green square is in other words in effect what you’d get with an 80mm lens on a full format camera.
Nikon has a webpage that simulates the different focal widths with the different types of cameras. Have a look at it and experiment to see what the different ranges and focal widths can get you.
Many actually want a crop camera for this exact reason. For example nature photographers for whom it is extremely important to have as much zoom as possible. Say they have a 300mm lens. On a full format camera that lens gives them exactly 300mm focal length, but on a crop camera, that lens would give them 480mm.
2) Aperture sizes
The aperture is the set of blades in the lens that opens and closes a circular opening in the middle when you shoot. Some lenses have few blades, others have more. The opening here is defined by what is called the aperture size and is represented by the “F/x.x” number. The smaller the x, the bigger the opening. We often want a really big opening, because it means more light and less depth of field. This means quicker shutter speeds, and a more interesting photo in that for example the background will be out of focus, making the subject really stand out. This out-of-focus background effect is called “bokeh”, and what is considered “good bokeh” is a discussion on its own, so I will not go into this here. It is however something to consider when looking for a large aperture lens, and several reviewers take this effect into close consideration when doing their research. In any case, the general rule of thumb for aperture is that the smaller the F-number (ie. the bigger then aperture), the better the lens is on paper.
3) Extra features
Some lenses have some special kinds of features. Some of Canon’s lenses come with “IS”, which stands for Image Stabilizer and is an active process inside the lens that compensates for slight movement. It helps make really sharp images while shooting handheld, and is a really handy function. Some of Nikon’s lenses has the same, but they call it VR, or “Vibration Reduction”. Another example is for example Sigma who makes some lenses with HSM, which stands for “Hyper Sonic Motor”. The idea here is that it is built to find focus fast and more importantly, quietly. There are so many different kinds of features that I cannot possibly list them here, but if you Google it, you will find it pretty quickly.
4) Physical build
This isn’t something I’ll get into here. Just hold the lens in your hand, and bring your camera to the store so you can try it out. Hold it, use the zoom, try to find the auto-focus on/off-button without looking for it, use manual focus ring. Just get a feel for it and decide if it feels good in your hands.
Lenses with pet names
Just like everything else, some lenses are so famous they have earned a pet name. I’m sure there are many of them, but I’ll only bring out a few here because I’m a big fan of them myself.
The kit lens: This one isn’t really fair to bring up here as this is not one particular lens. Most people start out with what is called a “kit lens”. This is a term that you’ll often see in photography forums and such. A kit lens, is a lens that comes with the camera when you buy a package deal, ie. both a camera body and a lens in one package. These lenses are usually not bad per se, but are often selected for being an all-round kind of lens, as well as being relatively cheap. If you are starting out and getting to know photography, this lens will cover your needs for a good while.
The nifty fifty: This lens is also not necessarily one particular lens, but there aren’t many lenses in the category. Roughly speaking Nikon and Canon has each theirs. (Others also make 50mm lenses, but I’ll get to why I bring out Nikon and Canon’s particularly).
What they are, are lenses that are 50mm wide with no zoom and a f/1.8 aperture, which is fairly large. There are also f/1.4 and f/1.2, as well as f/1 and even a rare few with even larger apertures than that. So why f/1.8? Why is this lens famous? Well for one it takes really good pictures. The pictures are very sharp, and with the large aperture of f/1.8 it will give you much light in those dark situations. It is however slow to find focus and is also noisy in doing so. It has a flimsy build and feels light and plasticy. Because it is made mostly out of plastic. So why is it awesome? Because it is probably one of the cheapest lenses you can get while also giving really good pictures! This lens is so popular that it has its own niche photography. People even make groups where they gather and share pictures taken exclusively by a lens like this. This lens, has personality and charm. This lens, is the lens that I personally think should be a kit lens for all cameras. This lens, is the only one that I’d say is an obligatory lens for anyone who enjoys photography.
The bokeh monster: Yep. It sounds alot like “the cookie monster” doesn’t it? That’s the “pun”. This is actually a really old lens. The Pentacon 135mm f/2.8. It does not have auto focus. It will very probably not fit your camera directly. They are not sold in stores anymore, so you gotta put your trust to eBay if you want it, where many of the lenses sold have some sort of damage. In addition, because it won’t fit your camera, you have to buy a socket converter so that you actually can attach it to your modern camera. This can in some cases result in you actually losing your “infinity focus point”, meaning that you cannot use this lens to photograph things that are farther away than a certain distance.So why the hell would you want one? Well, this lens is famous for its wonderful bokeh, but I’m sure you guessed that based on its name. It has an impressive 15 blades on its aperture, which gives it a really round and beautiful bokeh effect. Many consider it the example of the perfect portrait lens and many people just absolutely love its personality and how their images look when they use it.
“Well, if the lens is so incredible, why has no manufacturer made an attempt to recreate it?” They have. Producers like Zeizz, Canon and Nikon have all made their versions of this, and successfully so. Canon’s version even has received its own nickname: “The Lord of the Red Rings” (Canon 135mm f/2.0L USM) (it is an L-series lens, and all L-series lenses have a red ring on the end piece of it). The problem with these modern lenses is that they cost a whole lot of money. One of the cheapest ones that is still considered really good falls on around 10,000 NOK (1,600 USD). Many of the used Pentacon-lenses go on eBay for somewhere between 1,500 and 2,000 NOK (240-320 USD).
How to interpret the stats when researching a lens
Ok, so you’ve decided on a type of lens that you want, and now you are ready to do your research. Where do you go? One problem is that you cannot really just Google the lens you’re wondering about and read random blogs about it. I’ve burned myself doing that, and take it from me: It doesn’t always work out well for various reasons.
Me personally, I always go to www.dpreview.com (Digital Photography Review), but they are not the only place who do properly thorough tests of lenses. DPReview has thoroughly tested an impressive range of lenses, though it has not like they have tested absolutely everything. If they haven’t tested the lens you’re wondering about, then just look elsewhere for in depth reviews. It means nothing that its not listed there. (For example: They have not reviewed the Canon 135mm f/2.0L USM, even though this is an absolute beast of a lens).
Their reviews cover so many aspects of the review object that you’ll get an answer for more than you thought possible to ask. That said, you don’t always want to spend a long time reading about everything, so what I often do (because image sharpness is important to me) is to always check their interactive sharpness diagrams that can also set up two diagrams next to each other to compare lenses.
The image above is a screenshot of said diagram. Here comparing the Sigma 24-70mm F2.8 EX DG HSM with the Canon EF 50mm f/1.8 II, both on a full frame camera. First notice on the bottom left you have “focal length”. On the Canon lens, this is set to 50, and there are no other values available. This is of course because the Canon lens is a prime and has no zoom. These fields are sliders that you can interact with to see the image sharpness on the different focal lengths. There’s also a similar slider for aperture. What I’ve done here is compare two lenses at 50mm on aperture 2.8 to see which lens would fare the best using the same settings. Clearly, the Canon lens comes out on top. You can tell from the color of the image to the left in the diagram, but also by looking at the sharpness diagram.
This doesn’t thereby say that the Canon 50mm is a better lens, because the Sigma actually has zoom, and all zoom lenses fare worse the more you zoom in. The Sigma is therefore sharper on 24mm, than it is on 50mm. The only thing this tells me, is that if I want to do a shoot where I know I’m gonna use 50mm and I have time to choose, then the Canon is the better choice.
A difficult thing is that some lenses fare “ok” on one camera, but may fare pretty bad on a different one, so even this test is not necessarily bulletproof if they haven’t just happened to test the lens using your camera. Take the Tamron 18-270mm F/3.5-6.3:
On the left is the lens on a Nikon camera, set to 18mm at F/5.6, vs. on a Canon camera with the same settings. Pretty noticeable difference. Of course, other times it goes the other way around again, and Nikon gives the best results. (Even so, none of these results are very good…)
There are particular lenses for particular jobs. Some lenses try to be a lens to do all jobs in one lens, but these tend to give pictures of a reduced quality. Some may not care about this, and for certain jobs, you may not care about this. Sometimes you may not want to risk bringing along your top of the line equipment. That’s up to you.
You now know that if you want a high quality lens, then you want to find out what is in generally the best kind of focal range for what you want to do. Taking portraits? You need something in around 100mm range. (Maybe for example the Bokeh Monster?). Shooting at a crowded wedding? A wide angle lens at 10 or 14mm is probably a good idea. And so on.
Now you can start looking into what kind of lenses are available on the market by using for example Google to look for lenses that cover that range. Make a list of the lenses that are in your price range and take this list to for example DPreview.com. Here you can start looking into if any of the lenses has been tested and what they scored. Look particularly into the specifications that are important to you, and make sure you won’t get surprised after buying your new lens. And for the love of God, don’t go to the photography store to browse and buy a lens the same day you start looking for it. If you end up regretting your purchase it will be a lot of money lost as nobody will buy your lens for the same price you bought it, no matter how sparsely used it is.