How to choose your first lens

Choosing your first lens is more complicated than choosing a lens. Simply because you might not know much about the lens in general. Until now you did not have to choose one, you probably did buy digital cameras, but since they came with a built-in lens well you did not have much to say about it. Albeit, as I said in the episode CITM – How to choose your first DSLR, the lens is more critical than the camera body, and we are going to see this in details here.

Lenses are manufactured to fit a specific brand of camera body

There four major DSLR manufacturers on the market: Canon, Nikon, Sony and Pentax. Each not only builds camera bodies but lenses as well. However, the lenses are not inter-changeable across brands which means that you cannot attach a Canon lens on a Nikon and vice versa. Conclusion, the choice you made with your Camera body, will determine the lens brand you are bound to be associated with almost “forever”. I say this since you will upgrade your Camera body eventually in a few years, but you may have bought lenses in between, and all of them would not work on a new Camera body if you were to change for a new DSLR brand. However you could always sell them all, but from what I can tell, once you are chosen a comfortable camera body and build experience with it it is more likely that you will not switch brand.

Lenses are either made for Full frame sensor cameras or Cropped sensor cameras

We covered the differences between the sensor in The History of Photography and in How to choose your first DSLR. I have said earlier that Cropped Sensor cameras represent the majority of models out there and to make lenses more affordable, manufacturers started to make lenses built specially for Cropped Sensor cameras. In the Canon world, there are identified by EF-S, Nikon by DX. It is important to understand that while you can always use Full Frame lenses (EF for Canon and FX for Nikon) on both Cropped Sensor and Full Frame cameras the opposite cannot be. Should you ever be able to DIY mount the Cropped Sensor lens on a Full Frame camera body, you will suffer from very strong vignetting ( black edges around the exposure). That is due to the simple fact that Cropped Sensor Lenses are built with narrower glass elements since the Cropped Sensors are smaller than the Full Frame ( 1.6 for Canon, 1.5 for Nikon, Sonny and Pentax). So with a Full Frame sensor, there would not be enough information coming from the lens to fill the whole surface of the sensor. There are two factors that characterise a lens: the Focal length and the widest Aperture a lens can offer. That is why you may see me talking about my Canon 50mm 1.8 lens or my 18-135mm.

The Focal Length

The Focal Length is that value in millimetre that is written on a lens. It represents the distance from the glass element inside the lens to the sensor in the camera body. The Focal length of a length does not change depending on whether you attach it to a Full Frame Sensor Camera or a Cropped Sensor Camera. However what changes are the Field of View a lens provides when attached to a Cropped or Full Frame Sensor Camera. This is often a confusing part for young SLR photographers. We saw that Full Frame Sensor Cameras have a bigger sensor surface than Cropped Sensor Cameras. Therefore when the information coming through the lens reaches the sensor, it can collect more of it, so the light beams captured by the very edges of the glass element in the lens will be recorded onto the sensor. Consequently, the Field of View will be wider than the one recorded by a Cropped Sensor, as seen below:

Before Digital Single Lens Reflex Cameras there were Single Lens Reflex Cameras using film as the medium, and all films were more or less the same size and referred to as 35mm medium. Throughout decades, photographers have learnt to appreciate the Field of View that a specific Focal Length offers and also came up with rules around those basics to ease the practice of the art of Photography. Hence, still, nowadays you will often hear “on a 35mm equivalent”.  Here are a couple of examples: In the episode The Shutter, I have explained the phenomenon of Camera shake resulting in blurred exposure. To address this issue, I provided the following rule of thumb:

• The correct ShutterSpeed = 1/ Focal Length (on a 35mm equivalent camera =  Full Frame Sensor Camera).
• The 50mm lens has the same magnification as the human eye ( on a 35mm equivalent camera =  Full Frame Sensor Camera)

This whole “on a  35mm equivalent” can be a nightmare when talking to people but soon you will get the habit. It is a bit like the Widest Aperture is the smallest f-number (ref. Aperture).

The widest Aperture a lens can offer

As seen in the episode Aperture, most lenses would have a variable Aperture. For example, my Canon 50mm 1.8 lens offers me an Aperture of F1.8 at the widest and can be narrowed down to F22. Most lenses with a variable Aperture would enable you to go at least down to F22. The narrowest Aperture is never really the Aperture value you want to judge a lens on, mostly since the narrower the Aperture the less sharp it gets. However, the widest Aperture value is what you want to look at when reviewing lenses! The reason is that a lens that offers a wide Aperture is considered a fast lens. This is because of the wider the Aperture, the less fast your Shutter speed needs to be, meaning that when shooting in the low light condition you would not need to increase the ISO to compensate should you want to hand hold your camera for example. Or even if you are shooting Wide Life or Sports Photography, where the action needs to be frozen, hence a fast Shutter speed, you can rely on the wide Aperture instead of a high ISO which prevents you from having noise in your resulting exposure. However keep in mind the obvious affect of the Depth of Field when using a very wide Aperture such as F2.8 and below (Ref. DThe Creative Aperture: the Depth of Field) So if you find a lens that offers the widest Aperture of 2.8 vs. the same lens that offers 3.5 or even 5.6 you know that the first one is bound to be much better while very much more expensive! Looking at my Canon 50mm 1.8 lens that cost barely £100. Canon has the 50mm 1.4 lens that cost £250 and even a 50mm 1.2 L lens that cost £12000. The wider the Aperture, the bigger the glass element, more expensive to manufacture and to purchase subsequently.

The standard lens

We saw above that the 50mm lens offers the same magnification as the human eye provided it is attached to a Full Frame Sensor Camera. It means that if you took an exposure with this lens on a Full Frame, it would look no different, regarding magnification, from what you can see by yourself with your own eyes. Note: I referred to FFC because as you know by know, a lens manufactured for Full Frame Sensor Camera, as my Canon EF 50mm, once on a Cropped Sensor Camera, it will have a narrower Field of View. Subsequently, it will magnify the subject mating the Crop ration (1.6 on Canon, 1.5 on Nikon, Sonny and Pentax). Therefore my resulting image on the CSC will be magnified comparing to the human eye. A Standard lens offers no magnification, and this is why it has been the favourite one for Photojournalists and Street photographers who want to capture the true reality of life.

The Telephoto lens

This type of lens enables you to magnify the subject so it will appear bigger than what you can see with your own eyes. Subsequently, making it bigger it will give the appearance of being captured from a closer distance. This lens category is praised by Sport and Wildlife photographers since they need to capture the action without being close to it. In the other types of Wildlife photographers, you have the obvious paparazzi would need to expose someone from a mile way and still capture a piece of his/her action. One can consider that a lens is part of the Telephoto category when it magnifies the subject. Note: without bringing more confusion about the effect of Cropped Sensor on the magnification, I am sure some of you may think the following: “If I use a 50mm on a Cropped Sensor Camera, we know that it will magnify the subject, hence could it be considered as a Telephoto lens? A truly Standard lens for a Cropped Sensor Camera should be a 35mm?”. My personal answer is NO. When talking in general about lenses, for the sake of avoiding any confusion, we consider the absolute being the Full Frame Sensor. Hence you find the “35mm equivalent” written on most Digital cameras when referring to the Focal Length of a length.

The Wide Angle Lens

This category offers the opposite. It enables you to shrink the subject or whatever is within a scene. Why would you want that you might be asking? Well, if you are a Landscape photographer your goal is to capture a maximum in your exposure, and by shrinking what lays before him/her, you can show more of the scene. Think about the real-estate agent who wants to take a photo of a room. He/she either wants to make sure a maximum of that room is captured in the photograph or as often the case, wants to make you think the room is bigger than it is. This type of lens is praise also by Architects who need to capture a whole building. Although I thin, they would use a very strange and specific type of lens called “Tilt and Shift” lens. I will do an episode on this in the future. Here are 3 sample images that I took at three different Focal Length with the Canon 18-135mm. Those are not sharp, but they show the shrink and magnification effects:

Prime and Zoom lens

We call Prime a lens one that has a fix Focal Length, like my Canon 50mm lens. On the contrary, a length that enables you to change its Focal Length is called a Zoom lens. To not be confused with a Telephoto lens. Often one can hear: “you have a big zoom” when referring to the size of the length and implying you can capture things that are very far away. Well, it is not accurate. While Zooming implies magnification, it does not necessary mean that the magnification range of a lens will be more than of the human eye and therefore should not be confused with the range of a Telephoto lens. As an example, I am to purchase a 10-20mm lens soon, and as the description implies, this lens has a variable Focal length going from 10mm to 20mm. Hence it is a Zoom lens. However, it is a very Wide Angle length and not a telephoto. Surely it does magnify from 10mm to 20mm, but the magnification is still hugely smaller than the one of the human eye. Note: Prime lenses are globally reviewed as better quality regarding sharpness as Zoom lens. This is because you have more glass element in a Zoom lens than in a Prime. Hence more compromise to do to achieve different Focal Lengths.

Kit lens

A Kit lens is not a lens you buy from IKEA that you need to build yourself. It is the lens you get with a DSLR when sold as a bundle. Do not be fooled by what may appear as a bargain at first because it is not. Kit lenses usually have a variable Focal Length of 18-55mm with a variable Aperture of 3.5-5.6. They are so cheap you cannot, nor would you want to, buy it from EBAY. They are made entirely of plastic even the screwing mount (that attaches to the Camera body). Their quality is low. Personally, when I bought my Canon 60D, I went for the higher level kit lens if it can be considered as such, the 18-135mm. The quality so much better. It is a fantastic walk around lens that gives you a nice Wide Field of View at 18mm and a nice Telephoto magnification at 135mm. It has an Image Stabiliser, and the screwing mount is in metal.

3rd party lens manufacturers

While I started this post by saying that once you’ve chosen a DSLR brand, you are bound to use a lens that fit that brand, you can find three major 3rd party DSLR lens manufacturer on the market: Sigma, Tamron and Tokina. While at 90% of the time their lenses will be cheaper if not much cheaper than the main brand one (Canon, Nikon, Sony and Pentax), their qualities do often seriously challenge them as well. As a matter of a fact, the Wide Angle lens I told you I am about to purchase is the Sigma 10-20mm 3.5 which, while being still £200 cheaper than the Canon 10-22mm offers me better quality. Within Sigma, Tamron and Tokina, you can find different quality of lens like with Canon and their L Lenses. The Sigma 10-20mm comes in 2 versions:

• 10-20mm 4-5.6
• 10-20mm 3.5 (newer version with wider Aperture and improved lens glass).

Check the specs

Just like for the Camera bodies, you can find all the detailed specs of lenses online. Here is my favourite website for it: http://whatdigitalcamera.com, http://www.cameralabs.com and http://www.dpreview.com. An another interesting functionality you can find on high-level lenses is the USM (Canon), HSM (Sigma), SSM (Sony, SWM (Nikon). This is a little Ultrasonic motor inside the lens that speeds up dramatically the auto-focussing process, and it also does it in silence.

2nd hand lens

Just like with Camera body, and pretty any used gear, you cannot tell the quality of a lens by looking at a picture.  Lenses need special care and are aware of what you can find on lenses: Dust, Fungus, Scratches, Dents and cranky internal mechanism. So my advice would be to buy a used lens from a Camera shop as they would have done the appropriate check up of the product.

The Process Summary

Once you have defined your budget, you have decided on a DSLR manufacturers, agreed on the type of Photography you are most like to do, check the lens specs online to compare with equivalent models ( across all brand that manufacture lenses that fit your DSLR Camera body), go to the nearest Camera shop with an SD card and try the lens for yourself. Feel it, be your judge and if you do like it then either buy it there or online.