Photo: Jakub Vacek

How To Choose Your Camera Lens

If I were an amateur photographer just been admitted to the ultimate photo-store of my dreams, my mannerisms would suddenly change for the worse, and would most certainly resemble Scrat (Ice Age) lost in a world of acorns. Not knowing which one to pick and which one to leave I would mostly likely be confused, dabbing at things at random.

Choosing a right camera lens could easily become a predicament for the uninitiated. In a world of confusing acronyms, markings, definitions and formats choosing the right lens is more confusing than knowing which turn to take on Dupont Circle. Hopefully this tutorial will guide you to your dream lens(es).

Lens mount

If you prefer purchasing your lenses ‘the old-school way’, i.e.; going to a store and picking up the one you need from among many, the first question the clerk would ask is – “which mount?”

If you are an amateur this innocuous looking question would floor you right there. The lens mount essentially can be compared to the umbilical cord. It is an interface that connects the lens with the camera body. Whatever the lens does is actually on instruction from the camera body that is channelized via the lens mount.

Lenses designed for a specific mount won’t operate on other mounts, unless you use a mount adapter. The most popular lens mounts are Canon’s EF and EF-S, Nikon’s F and Sony’s A mount. It is important to know the mount type of your camera to begin the hunt for lenses.

The lens mount can be made of both plastic or metals. The heavier, expensive & professional grade lenses are mostly made of metal mount.

Format

There are two major current DSLR formats based on the size of the sensor. (a) Full-frame and (b) APS-C. A full-frame sensor mimics the size of the erstwhile 35mm film format with the dimensions 36 x 24mm. An APS-C sensor is slightly smaller and there are two main popular options – (a) Nikon’s 24 x 16mm and (b) Canon’s 22.3 x 14.9mm.

I see a question coming, “so what’s the big idea with the sensor size, anyways?” Well, the sensor is like a bucket and the incoming light is like raindrops. Bigger the bucket the more water you can collect. Evidently, this means your point and shoot, despite all the promotions, cannot hope to match an APS-C DSLR. The same way an APS-C DSLR cannot hope to match a full-frame DSLR.

Lenses designed for APS-C DSLRs are not advisable to be used with full-frame bodies unless you want large black corners in your images. Lenses designed for full-frame DSLRs, however, works without major issues on smaller bodies crop bodies (APS-C). The morale of the story – if you have plan for a full frame DSLR in future, buy full frame lenses now. So that you don’t have to change your entire lens collection later. Just change your camera body instead. Read more on sensors here

Lens types

All lenses are divided into three basic types based on their focal lengths – (a) wide, (b) standard and (c) telephoto. Of course these can be further sub-divided, based on their ability or inability to zoom, in the following two categories – (a) zoom and (b) prime. There are some other special types of lenses available for example (a) Macro Lens (b) Tilt & Shift Lenses.

Wide angle lenses – Any lens that has a focal length of less than 35mm is considered as a wide angle lens. Wide angle lenses provide a wider angle of view (thus the name). They also have an effect of pushing the background away and bringing the foreground closer.

Canon 16-35 f/2.8L, Canon 17-40 f/4L & Nikon 16-35 f/4 – Wide Zooms

Standard lenses – these are lenses in the range 35mm to around 60mm. They are referred to as standard lenses because they don’t tend to distort or compress the background and the foreground in any way. Additionally, the standard 50mm lens is widely considered to give the same angle of view as the human eye. This is one of the reasons why street photographers as well as journalistic photographers prefer using the 50mm lens with their full-frame DSLRs.

Telephoto lenses – These are highly sought after by sports, wild-life and even amateurs because of their ability to capture images of distant subjects. These lenses usually have a focal length of more than 75mm and can go up to 800mm for standard production models.

Nikon AF-S NIKKOR 800mm f:5.6E ED VR – Tele Photo lens

Telephoto lenses can also offer what is known as perspective compression, compressing the background and the foreground by bringing them together. This has some utilities in sports photography e.g.; where you need to show all the players on the same plane.

Zoom lenses – These are lenses which have variable focal lengths and can switch between these by a turn of the zoom ring on the lens barrel. Pretty handy when you are a lazy bum and want to photograph without breaking a sweat.

Tamron SP 150-600mm F:5-6.3 Di VC USD – Zoom Lens

Prime lenses – The ultimate tool for sharp images, fine bokeh and of course a lot of self-gratification, prime lenses have been the professional’s choice for years. They have a fixed focal length accompanied with fast maximum apertures helping you to make crisp images.

Macro lenses – These are specially designed lenses allow a photographer to fill the frame with even the smallest of subjects with higher magnification for creating a life-like image. A life like image means, the image is projected on to the sensor at the same size as it is in real life. Read more on macro photography here

 Canon EF 100mm f:2.8 L IS USM – Macro Lens

Tilt & Shift / Perspective control lenses – These lenses offer photographers an extraordinary degree of control on depth of field and perspective. Shift movements enables lenses to look up or down without tilting the camera, eliminating the ‘converging verticals’ effect that can spoil architecture images. Tilt movements can rotate the plane of focus to either extend or shorten depth of field. A handy feature in landscape or still-life photography.

Things to consider before buying a lens

Aperture

Aperture can be compared to the pupil of the eye. They have the same function as the pupil, controlling the amount of light that hits the back of the eye, which can be compared to in this case the sensor of the camera. Lens aperture can be both constant and variable.Usually expensive zooms & fixed focal prime lenses have a constant aperture. Lenses with constant F number are usually bigger, heavy & more expensive than usual. One of the advantage of having a lens with constant aperture is, aperture number remains fixed as you zoom in or out. On the other hand lenses with variable aperture number (f/3.5-5.6) aperture value changes. for example Canon EF-S 10-22mm f/3.5-4.5 USM Lens. It means, at 10mm the maximum aperture number is f/3.5 and as you zoom in towards 22mm the max. aperture number will become f/5.6. Lenses with variable aperture number are usually small, light & cheaper.

Large vs Small aperture | Photo: Shawn Chen

The bigger the aperture (smaller aperture number) the more is the quantity of light that sets in. In low light situations or when you want to freeze the action in broad daylight, bigger apertures certainly gives you an advantage. Unfortunately they are not cheap. For example, Nikon AF-S 70-200 f/2.8 VR II lens

Wider apertures are also good for capturing bokeh or soft out of focus background and foreground. This helps to isolate the subject from the surroundings. This is suitable in both sports and wildlife photography. The same effect is also sought after in mid-range tele-lenses such as the Canon EF 85mm f/1.2 L USM II lens (Amazon | Adorama | B&H) which is widely used for portrait photography.

On the other hand smaller apertures are suitable for creating greater depth of field to make almost the entire frame to be acceptably sharp. It is specially important in landscape and architecture photography. However smaller apertures needs a longer shutter speed may increase chance of image shake.

Diaphragm blades of Aperture & shape | Photo: Pascal

Aperture Diaphragm

Number & shape of diaphragm blades also play a important role in image quality. The 9 blade-rounded diaphragm creates an attractive blur to the out-of-focus areas of the image than 5 blade-rounded diaphragm.

Auto-focusing vs manual focusing

All Auto Focus lenses lenses will focus manually. There is a simple auto focus on/off switch that allows you to switch from auto to manual focusing. Manual focus lenses only allow you to focus manually. Some manual focus lenses you will be able to get a AF confirmation. Most nikon manual focus lenses are compatible with latest model camera. However, You won’t be able to use canon manual focus lenses (FD) on AF camera bodies (EOS Mount), unless you use some FD-EOS mount adapter.

Auto-focus motor type

Auto focus motors determines auto focus speed of a lens. Doing so, it also makes sound. Most auto-focusing sounds are acceptable and may not be a problem for many. Sometimes a complete silence is needed and situations like these demand ultra quiet lenses. Nikon’s AF-S lenses powered by SWM (Silent Wave Motor) for example, is a great piece of technology that offers super quiet auto-focusing. Canon uses USM (Ultra Sonic Motor) for this purpose.

Full-time Manual Focusing override

This brings us to the convenient feature of full-time manual focusing. This is available in most of the high-end lenses from major lens makers. This feature allows you to switch between auto to manual focusing without having to flick a switch. This saves a lot of time in real life situations where precise corrections can be made to where the camera thinks is the point of focus and where you want it to focus at.

Image stabilization

If you are a Sony or a Pentax user you are blessed with body-based image stabilization. This makes each and every lens that you buy for your camera to be stabilized by default. For Canon and Nikon users, however, you have to choose lenses that come with image stabilization, i.e., if you need it.

If you are shooting mostly in broad daylight and or using a tripod then image stabilization is something that you can forgo. After all why pay for something that you would never use? Well that is one way of thinking. The school of thought is you may not know when you might need it. So, if the difference in price is not much you might as well opt for a stabilized version. Its a good & handy features to have.

Build Quality

It is an important factor for photographers. As a keen photographer often you have to face the elements. thats why it is important to make sure your gears is capable of handling the odd bumps and knocks. manufatures use both plastic & metal for lenses. Certainly, metal construction These lenses are moderately to very expensive but are worth their price tag in terms of the advantage they provide. Canon’s L series lenses or Pentax’s weather sealed lenses are great choice for a quality glass. In an urge to shoot professional quality photos, in the most demanding of circumstances, photographers are looking for not only the best optical quality but also the best build quality.

Weather sealed/weather resistant

This is a feature most nature & sports photographer want to have in their lenses. It gives the lens capabilities to handle splashes, hail, snow, dust, dirt to the some extent. Apart from the lenses, your DSLR body should also have weather sealing for maximum weather resistant. Usually higher end professional and semi-professional DSLR models (Nikon D4, Canon 1DX) come with this feature. Canon, Nikon & Pentax has a series of cameras that come with weather sealed bodies, which are extremely well built.

Internal focusing and Internal rotation

On some lenses, the front of the lens rotates and some lenses extends out off the lens while focusing or both. Rotation of front elements is a big deal if you are trying to use a polarizing filter on your lens. Effect of Polarizing filter depending upon how it is oriented. For example you set your polarizing filter just how you want it. But the moment you start focusing, the polarizer also start spinning around along with your focusing elements and loses it’s effect. Not good, now you have to re-do it. same way during macro photography if your lens’s front elements extends, it may accidentally hit or scare the subject during focusing and ruin the settings.

Lens manufacturers use Internal focusing (also known as IF) & Internal rotation mechanism to overcome this issues. These are special lens designs in which focus is achieved by moving only the inner lens group(s), without rotating or moving the front lens element(s). The physical size of an internal focusing lens does not change during focus, nor does the front of the lens rotate. As a result front of lens doesn’t extend our forward off the lens. This is very use full using smarter looking petal shape lens hoods.These mechanism also help to keep the lens size more compact. One issue internal focusing lens can have is that the true focal length of the lens is reduced when not focused at infinity. So, make sure that the lens you get has a non-rotating front element and internal focusing mechanism.

Lens Elements

Lenses usually suffer from various dispersion and aberrations and may cause loss of sharpness & contrast. Most common aberrations are spherical & Chromatic (coma). To tackle or minimizes them lens manufactures use some special lens elements.  For example for correcting chromatic aberration (color fringe) Canon uses their own Fluorite and UD (Ultra-low dispersion) lens elements. Same way Nikon’s version is called ED (Extra Low Dispersion) and Sigma’s SLD (Special Low Dispersion). To correct Spherical aberration manufacturers use Aspherical lenses. Thats why how many UD/ED/SLD or Aspheric element used in that particular lens in important.

Optical structure of AF-S DX Nikkor 18-300mm f/3.5-5.6G ED VR lens

Lens coating

Ghosting & flares are the two common problem of lenses. They are created due to reflexion & re-reflexion of light on the surface of the lenses. Results secondary images and causes unsharp images. The more the lens elements the more the reflexion. That’s why zoom lenses suffer more from ghosting & flares. manufacturers use different types of lens coating technology on lens surfaces to reduce surface reflections. For example Pentax uses Super Protect (SP) coating, Nikon uses Super Integrated Coating (SIC) & Nano Crystal Coating. Regardless their names, their main job is to reduce Ghosting & flares and deliver sharp images. So without coatings, though, modern lenses could simply not exist. Always take care while cleaning lenses, you may damage lens coating.

Some important tips to consider

While buying multiple camera lenses, it is a good idea not to overlap their focal lengths (zooming length). Suppose, you plan to have 3 zoom lenses and you want to cover 17-200mm. It is a better to choose a combination like 17-35, 24-70 & 70-200  not  17-135, 18-50 & 28-200. These numbers are just a GUIDELINE, your need is more important. Try to keep a Macro lens in your bag. Benefits of having a macro lens is, it can serve you as a macro, prime & portrait lens. In terms of image quality they outperform any zoom lens. It can be handy when image quality matters.

Choosing a right lens for your type of photography is very important. They serves you longer than your Cameras. A camera model is usually replaced by the new models in very 1-3 years or even sooner. On the other hand for good lenses, this product cycle is more than 5 years. That’s the reason it is wise to invest on lenses than Camera bodies. Bodies will come & go, but a good quality lens will serve you for decades to come. Moreover, they retain their value well in second hand market, in case you want to upgrade later.

Where to buy?

You can buy your lenses & photography accessories in many ways. Some people like to buy used lenses. For that Craig list is a good place. Most people go to their local camera store to buy their camera & lenses. It has some advantages. You can test & feel them in store personally. You can also take suggestion from experts at store. However it is difficult to compare prices & deals. For that shopping online is the best options. You have to be careful about scammers though. Don’t go for too good to be true deals. It is better to stick with some reputed online store like Amazon, Adorama, DigitalRev & B&H to name a few. Sometimes near new refurbished lenses are available at discounted price directly from manufacturer like Canon.

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