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Which Lens to Buy

Canon 5D camera and Canon 600 f5.6 L series lens 


Canon 5D camera and Canon 180 f3.5 L series lens

I teach photography on a regular basis. One question that constantly comes up is “what lens should I buy?” There are numerous ways by which I can approach the answer. First I try to establish if the participant is happy with their current camera (brand and model) or is likely to consider upgrading in the near future.

If they’re prepared to upgrade I next determine their preference for wide-angle or telephoto photography. In other words do they want to photograph wide vistas or to bring the subject closer and separate them from their surroundings? If their preference is for wide-angle photography I suggest they purchase a full frame digital camera like the Canon 5D Mark II or the Nikon D700. Such a system would be well suited to a range of landscapes, environmental portraits and visually dynamic images where the subject is positioned very close to the camera and, thereby, rendered larger than life and separated from the background through a sense of extended space and exaggerated perspective.

Those folks interested in sports, surveillance or candid photography will likely be hoping to magnify their subjects and isolate them from their surroundings. Telephoto lenses are for them.

Please note: People often refer to their lens as a zoom lens. But what does that mean? The vast majority of lenses are still made for film cameras, despite the fact that they are used on the type of digital camera that allows you to interchange lenses. These cameras are commonly referred to as DSLR (Digital Single Lens Reflex) cameras. When educators are talking about lens focal length (e.g. 24mm, 50mm or 300mm) you can generally assume that they are talking about how a given lens behaves on a film or full frame digital camera.

So, let’s say you have a passion for surfing photography. You have a Canon 5D (full frame) camera and your 70-200mm zoom lens just isn’t powerful enough to render the subject as large as you’d like. So, which lens do you buy? Though only you can decide, for what it’s worth, here’s my advice.

Put together 5 or 10 images that illustrate you’re average surfing photograph. Based on the average how much larger would you like the subject to be. With the image at the top of this post as an example you might wish your subject were 4 times larger. Let’s imagine you’d made the image in question with a 70-200mm zoom lens at maximum magnification (200mm). Simply multiply 200mm x 4 to arrive at your desired focal length. Now, before you fall off your chair, there are several ways to achieve the desired magnification equivalent to a 800mm focal length lens.

Firstly keep your current full frame camera and spend many thousands of dollars on a new 800mm lens. You’ll also need to employ an incredibly heavy and robust tripod as well as a Sherpa to help you carry it around. You’ll become a point of attention on the beach and may well be pestered with all the “hey mister” questions you could image.

The second option is to purchase a camera with a sensor that is physically smaller than that found in a full frame camera. This includes your common, everyday Canon and Nikon bodies. In the case of the average Canon camera you need to multiply the actual lens focal length (e.g. 500mm) by the camera’s magnification factor (e.g. 1.6X) to arrive at the effective focal length that particular lens produces on the smaller sensor camera. So for far less money and considerably less weight you now have a more manageable lens with a faster maximum aperture. To ensure you don’t rip the camera’s bayonet mount off it’s relatively light body make sure you attach the lens to the tripod, via the tripod collar mount, rather than attaching the camera directly to the tripod.

The third option is to place an Extender or Tele Converter between the camera body and the lens to increase the effective focal length. Adding a 1.4 extender to a 500mm lens will result in a 700mm focal length, while a 2X extender (or tele converter) will produce a 1000mm effective focal length. Be aware that extender (tele converters) result in a loss of light between 1 and 2 stops. 

© Copyright All Rights Reserved

Glenn Guy, Blue Sky Photography


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