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Through the Gadling Lens: choosing the right lens
Generally, lenses are described by their focal length. A quick Google search of the term "focal length" returns some fantastically 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."
Here's how I like to remember it: the larger the focal length 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 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 stand 10 feet away from an apple sitting on a table, the photograph you take with a 35 mm lens will have a lot more background and a lot less apple; with a 100 mm lens, the picture will have a lot more apple and a lot less background.
Clear as mud? Not so much?
Okay, let's look at a few practical examples. (Note: all of the following images are taken right out of the camera -- I didn't do any cropping, or processing, other than to size them to fit on this post.) I asked convinced coerced my 4-1/2 year old daughter Alex outside to act as a model, and took several pictures of her, using different lenses. I asked her to stand on the curb, while I switched out lenses. That's her on the left:
Isn't she cute?
Okay, so the first shot I took, I used a 50mm lens. In general, lenses that are between 35mm and 70mm are called "normal" lenses -- in other words, when you look through the viewfinder, what you see is pretty much what you would see without the viewfinder -- everything looks about the same size, you don't see any more detail than you would with the naked eye, that sort of thing. Disposable cameras, for example, usually have lenses between 35mm and 70 mm. So taking the shot from the opposite curb, like so ...
... the image of Alex looks like this:
A perfectly suitable shot, and the kind of image that conveys exactly what I saw at the time that I saw it. This sort of lens works if you're going for street photography, or documentary-style photography.
But watch what happens when I switch my lens out for a 200mm lens. The following image was taken at the same spot, on the opposite curb from Alex:
See? All of a sudden, it's like I was standing right in front of her, even though I'm still standing across the street on the curb. She looks bigger in the shot (and you can see a whole lot more detail); however, I've lost a lot of the background (i.e, you can't really see the house or the trees anymore). 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 actually 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 (see the photograph at the top of this post), and therefore very unwieldy. On major trips I do usually take this lens with me, but I generally only devote one day to using it (getting lovely intimate shots of people talking to each other at a cafe, or otherwise interacting), and then put it away for the rest of the trip, instead using a lens with a smaller focal length (usually between 50mm to 100 mm).
Speaking of 100mm lenses, let's say you don't mind if your subject knows your taking her picture -- and in fact, you want to get a nice tight portrait shot. Generally speaking, lenses with focal lengths between 75mm and 135mm are known as "portrait lenses," and they enable you to take lovely, magazine-cover-shot type images of people.
And so, grabbing my 100mm lens, and standing right here, about three feet away ...
... I'm able to take a lovely tight shot of Alex's face, like so:
Now, is it possible for me to take a shot this close to Alex using the 200mm lens? It is, but I'd still have to stand about halfway across the street to do it, in order to get the focus right. And I probably couldn't take a shot like this with the 50mm lens, because I would have to stand really close to Alex to take the shot, and would likely end up with a really blurry shot, because I would be too close for the lens to get a really sharp focus.
For what it's worth, I always carry my 100mm lens (or a lens which "passes through" that focal length, like a 70mm-120mm zoom, for example), particularly when I travel; primarily because I love portraiture, and I love shooting the faces of the people who are native to the countries I visit.
Finally, let's take a look at a macro lens: the type of lens that let's you get really up close and personal. Again, I'll use Alex as a model, but this time I'll get very, very close to her (about 8 inches away):
And -- you're going to love this -- check out how much detail I can capture of her here:
See how you can make out every eyelash in this photo, every tiny contour of her skin? Macro shots are beautiful for grabbing very tiny details, sometimes in breathtaking ways. And there's no other kind of lens that can get this sort of detail than a macro lens -- other lenses just can't focus that well.
Now, obviously, you're not likely to walk up to an individual, get all up in their personal space and shoot their eyeballs. But macro lenses can be really fantastic for getting details of, say, the bumps on the back of some weird-looking tropical insect, or the stamens of a truly exotic flower. I always carry my macro lens with me if I'm going somewhere known for its beautiful flora and fauna -- I never know what I might get.
Finally, for those of you with point-and-shoots, don't despair: these days, point-and-shoots have wonderfully wide ranges of focal lengths for their built-in lenses. For example, the following two shots were taken with my Nikon Coolpix. According to the Nikon website, the Coolpix has a focal length range of between 28mm and 112mm.
So again, standing on the opposite curb from Alex, here's a shot at approximately 28mm (also called a wide-angle shot, used for architecture or landscapes):
(Notice now, how much more background I get than even the 50mm shot at the top of this post? Although Alex is tiny in the shot, now I not only get the house and the two trees, but the next-door neightbour's house as well!)
And here's a shot zoomed in at 112mm; this time, again, standing on the curb across the street from her:
Whew -- that's a lot to cover in one post! Hopefully, this helps you better understand what different camera lenses can do, and when they're appropriate for your favourite type of photography -- and for those of you who like crib sheets, there's a great one covering the kind of photography each lens is best for here. As always, if you have any questions, or would like me to cover anything specific in an upcoming post, please feel free to let me know in the comments below, or e-mail me directly at firstname.lastname@example.org. I'm looking forward to hearing what you have to say!
Karen is a writer and photographer in Houston, Texas. You can see more of her work at her site, Chookooloonks.
And for more Through the Gadling Lens, click here.