Choosing Lenses

ChoosingLenses - title

Chances are your digital SLR camera came with a lens (“kit lens”) and chances are when you’ve poked around with that lens you loved it more than any point-and-shoot you’ve ever used.  You’ve noticed that the “zoom” ability is greater, and that you can fill the frame with more subject if you desire.  That’s fantastic.  Welcome to the world of SLR.

Now you’ve been using that kit lens and it’s great, but you’re ready to upgrade to bigger and better.  This article is designed to help you in choosing the right camera lenses and explain what the differences exist between lenses.

The bad news is you’re in for a sticker shock.  Top quality lenses run you more than perhaps the camera body itself.  Hold on, don’t give up.  Here’s a secret: it’s worth it.  Lenses do the majority of the creative work for the photographer.  Don’t think so or not sure?  Well, at the next wedding you attend, check out the photographer and all the different lenses he carries to switch in and out of the same camera body.

So, if you’re going to be spending even more money, I’m sure you want to spend it wisely.  You certainly don’t want to spend $500-$1500 (or more!) on a lens you will never use, or at the very least, won’t do the things you want it to.

The two features of lenses – focal length and aperture – are the two features you are paying for.  More expensive lenses have “better” or at least broader focal length, and generally a faster (or wider) aperture.  Canon lenses, which I use, have a class of lenses called the “L” class.  These lenses are considered to have better overall optics, durability and are considered their professional line.  Canon lenses with similar focal lengths and apertures will be more expensive if they are L lenses.  You’ll notice them by either the red line at the end of the lens, or their grey-white color.

Now, let me start with focal length.  Focal length is essentially the “zoom” of the lens.  It is the reading, in millimeters, that  names the lens.  Most kit lenses are zoom lenses of 18-55mm (millimeters), meaning the lens can zoom from 18mm to 55mm.  Focal lengths of lenses vary from single digits  (8mm) to triple digits (400mm).  Smaller focal length lenses have a wider angle or field of view.  Imagine trying to a take a picture of a group of people, the smaller the focal length, the closer you could stand and still have everyone in the picture.  Larger focal lengths are more “zoomed in.”  If you’re in the upper deck of a football stadium, you would need a “long” or high number focal length to be able to capture a picture of the quarterback.  Generally speaking, lenses with focal lengths of 35mm or less are considered wide angle lenses.  They will give a wide field of view and are useful for pictures of sweeping landscapes or large groups.  Lenses with focal lengths of 100mm or greater are considered telephoto lenses.  They have use for action photography or nature photography – anything where your subject might be far away.  Premium focal lengths, meaning ones which will cause the lens to be more expensive, will be on the high or low end.

Aperture is of course the other feature of a lens that dramatically influences cost.  To put simply, you pay more for a faster lens.  A lens with a wider aperture (smaller f stop) is going to be more expensive.  A perfect example of this is Canon’s trio of 50mm lenses.  The slowest, a 50mm f/1.8 lists for only about $120, which is a very solid deal and makes for a great first non-kit lens.  The middle version, the 50mm f/1.4 lists for about $350 and is also a great deal. The cream of the crop, with the “L” designation is the 50mm f/1.2 which lists for around $1,600!  As you can see, to move up a full stop from f/1.8 to f/1.2, you’ll pay an extra $1,500.  Is it worth it?  It is if you need that extra f stop to shorten your shutter time, or narrow your depth of field.

All lenses will have equivalently small apertures of f/16 or f/22.  We call lenses with larger apertures faster because they have the ability to let more light in for a given time.  This allows the photographer to use a faster shutter speed.  Larger apertures also blur the background more for artistic effect.  [see related article]

Some lenses will have a fixed aperture while some will have an aperture range.  Fixed apertures are easy, as the maximum aperture stays constant through the focal length zoom range.  Other lenses (like the Canon 18-55 kit lens) vary in maximum aperture.  As a rule, the maximum aperture decreases as the camera’s focal length increases.  For example, on Canon’s kit lens, the 18-55mm f/3.5-5.6, at 18mm, the widest view of the lens, the maximum aperture is 3.5.  However, as you zoom in, increasing the focal length to 55mm, the maximum aperture will increase in number (decreasing in size) such that by 55mm, the aperture maximum is only 5.6.  In reality, you’ll likely hit the 5.6 aperture size well before 55mm.

Of course the price of a lens is also heavily based on overall image quality.  You’ll find some third-party lenses with focal lengths of 500mm priced at $250, why then does a Canon 400mm f/5.6 cost around $1500?  Image quality.  Image quality, unlike focal length and aperture, is tough to quantify.  MTF charts attempt to display the overall sharpness and resolution of a lens but that is beyond the scope of this article.  If you really want to get into the nitty gritty when comparing lenses, go to the MTF charts.  Remember though that MTF charts between different companies do not correspond and therefore you can’t compare the MTF chart of a Sigma Lens to the MTF chart of a Canon one.  I explain how to interpret MTF charts in another article, though I warn you, they are quite difficult to decipher.

One last thing to mention about lenses are the so called “Prime” lenses.  These lenses have a fixed focal length, meaning there is no zooming in and out.  These lenses require the photographer to move closer or farther from the subject as needed.  I personally like Prime lenses for one reason and one reason only.  I believe that Prime Lenses are sharper at their focal length than a zoom lens at the same focal length.  If you don’t believe me, you can compare MTF charts.

Below are some Canon and Nikon lenses available on amazon.com. Check out my thoughts on the equipment I carry around.

 

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