occasionally technical tuesdays: on choosing a camera lens

You thought I'd forgotten about Occasionally Technical Tuesdays, didn't you?  Of course not, I'd never abandon you, my lovelies.  So, since last time we discussed the most common question I receive -- how to buy an SLR camera -- today I thought we could talk about the second most frequent question I'm asked:  how to choose a camera lens.  And since this subject is better shown than taught, strap yourselves in -- you're in for a photo-filled post.  So let's begin.

Generally, lenses are described by their focal length -- the number that you hear with the "mm" after it (e.g., 50mm, 100mm, 70-200mm, that sort of thing).  A quick Google search of the term "focal length" returns some fabulously technical definitions -- my current favourite is "The focal length of an optical system is a measure of how strongly it converges (focuses) or diverges (diffuses) light.  A system with a shorter focal length has greater optical power than one with a long focal length."

Which, you know, when it comes to my camera, tells me exactly nothing.

Here's how I like to remember focal length

The larger the focal length number of a lens, the bigger the subject looks, and the less of the background you'll see in your shot.

The smaller the focal length number of a lens, the smaller your subject will look in your photograph, but you'll be able to see a whole lot more background.

In other words, if you took a picture of an apple sitting on a table, the photograph you take with a 35mm lens will have a lot more background and a lot less apple than if you took the shot with a 100mm.  With the 100mm, you'll have a lot more apple and a lot less background.

Clear as mud?

Anyway, the point is that often, the decision about what lens you should buy rests on what kinds of photographs you'll want to take -- portraits, or scenery, or intense close-ups or whatever.  And this will all become much clearer when we take a look at some practical examples (note:  all of the images in this post, while they have been processed, have not been cropped in any way, so you can see exactly what each lens captures)

So on Friday, I enlisted Alex's help (before the humidity got to her hair) to help me illustrate.  I took her to a neighbourhood street, and stood her on the curb, like so:

Now, for the next series of photographs, I was standing on the opposite side of the street, like so:

The first image I'm going to show you was shot with my 50mm lens.  In photographer parlance, a 50mm lens is often called a "normal" lens, which is to say that what you will photograph with a 50mm is pretty much exactly what you'll see with your naked eye -- the subject won't look any closer that she actually is in the resulting shot, nor will you get any of the stuff that would normally be out of your peripheral vision. 

So, taking Alex's photograph from across the street, the resulting image looks like this:

50mm lens

See?  It's totally believable that I was standing exactly across the street from her, and it's a perfectly suitable shot conveying exactly what I saw at the time that I saw it -- no more, no less.  This sort of lens works if you're going to be doing any street photography, or documentary style photography.  In fact, I'm of the opinion that every photographer should own a "fixed focal length" (i.e., non-zoom) 50mm lens, as it's a great standard, "normal" lens to use when you're learning photography, allowing you to do all kinds of shots (including portraiture, which you'll see later in this post).


As I mentioned above, any lens with a smaller focal length than a 50mm lens will show more background and make the subject look smaller -- these are called "wide angle" lenses.  Wide-angle lenses will actually pick up more of the image that you would normally see in your peripheral vision -- in fact, if it's wide enough, it will pick up even more than that.  For comparison, take a look at the shot below, that I shot with my 35mm lens:

35mm lens

See how much tinier Alex looks?  And I was standing in the same spot.  Notice also that with the 35mm, I can now capture the entire roofline of the house in the background, as well as more of the pine tree to Alex's right (the left hand side of this picture).  Wide-angle lenses are great if you're into photographing scenery shots, and come in far shorter focal lengths than 35mm -- the lens I used for my Galveston shots went as wide as 16mm.  If you're into scenery shots, wide-angle is where it's at.


So now you know about wide-angle lenses, and normal lenses:  the next are telephoto lenses, or lenses with focal lengths greater than 50mm. Telephoto lenses act sort of like telescopes:  they bring your subject closer to you, making them look larger, and reducing the amount of background in the shot.

To illustrate, the following are shots taken with my 70-200mm zoom lens (a zoom lens is a lens that can move from one focal length to another).  This first was shot at 70mm:

70-200mm lens (shot at 70mm)

Again, this photograph was taken from across the street; however, notice, compared to the 50mm photograph at the top, Alex looks much bigger, and less of the background is showing up.  And when I zoom to 200mm:

70-200mm lens (shot at 200mm)

... it looks like I took the shot standing right in front of her, even though, again, I was still standing across the street from her!  The beauty of this lens is that you can take wonderfully intimate shots of people (e.g., the old men playing chess in the park) or wildlife (the boa constrictor wrapped around the tropical vegetation) or sports (that touchdown made by only inches) without getting in the way of the subject -- the old men, boa constrictor or running back will likely not even know you're there.

The downside of this sort of lens?  This bad boy is huge, and therefore very unwieldy.  It's definitely one of my favourite lenses, and I tend to use this a lot when I'm shooting at a friend's wedding or other events where there's a lot going on (getting a lot of lovely intimate shots of pepole talking together, or otherwise interacting), but otherwise, it often stays at home.

Now say you're really into portraiture, and you don't care if your subject knows you're photographing them -- in fact, that's sort of the point of your photography.  With most lenses, you can get to within 2 feet of your subject and take lovely photographs without losing any ability to focus.  For example, photographing Alex from two feet away with my 50mm, from this position ...

... results in lovely shots, like this:

50mm lens

If portraits are what you like, you definitely want to get what photographers call a portrait lens -- something with a focal length of between 50mm, say, and 100mm.  Wider than a 50mm will tend to distort the faces of your subjects, making them look wider than they are; and more "telephoto" than 100mm you're going to end up standing quite a bit away from your subjects to take the shots.  Personally, I'm in the market for one around 85mm -- I'll let you know what I get.

And finally, perhaps you're looking to shoot really really close-up shots, getting inches away from your subject, so you're practically on top of them, like this:

Then what you're in the market for is a macro lens (or what Nikon inexplicably calls a "micro" lens).  These lenses pretty much perform exactly like their associated focal lengths would do -- i.e., a 60mm macro lens performs like a normal 60mm lens, a 100mm macro lens perfoms like a normal 100mm lens -- however, macro lenses also allow you to get mere inches away from your subject without losing any focus.

So, while a normal lens would start to lose focus and result in fuzzy shots if I stood any closer to Alex than 2 feet or so, my 60mm macro (or "micro" lens, in my case), allows me to get mere inches from Alex, capturing a photo like this:


60mm macro (micro) lens

See how you can see the details in every hair of her eyebrow and eyelashes, as well as the texture of her skin?  As another example, the photograph at the top of this post was taken with my micro lens, and to give you an idea of how tiny those flower are in real life, they're the same flowers that are on the little tree to Alex's left in the first 50mm shot above. 

In other words, macro lenses let you get in close.  So when you want to get really tight shots of the details of a flower, or capture the raindrops on a leaf or even examine the tiny markings on an insect, really, a macro lens is the only way to go.

So that's about it -- you now know almost everything there is to know about focal lengths of lenses.  Remember:  if you're shopping for a lens, the most important thing to think about is to consider what kinds of photos you want to shoot, and then choose the focal length accordingly. 

One more hint:  the second thing you're going to want to consider is the aperture number of the lens (the part of the lens description that has a decimal number in it, like 1.4, or 3.2 or whatever) -- but aperture is a concept that we'll explore more deeply in another post.  I will leave you with this thought for now, though:

The smaller the aperture number, the more desirable the lens generally is, and therefore it will be priced accordingly.  My general rule is that you should always buy a lens with the smallest aperture number you can afford.

And I'll tell you why on the next Occasional Technical Tuesday.  Until then, friends, happy clicking.


Occasionally Technical Tuesday is a new feature here on Chookooloonks, where we'll tackle topics like choosing a camera, how a camera works, how I choose lenses, how I use Photoshop, how I pack for a photo trip, that sort of thing.  You can see an entire index of subjects we've addressed here.  I'm no expert, but I'll share what I know, occasionally.

Images:  Photographed with my Nikon D300, with the lenses as shown above.  I normally would tell you what my camera settings were on these shots, but I don't want to confuse things any more than necessary on this post.  I'll go back to sharing settings tomorrow.


Song: Hey ya! by Outkast.  Shake it like a Polaroid picture.