Jodie Coston: Lesson 3
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 To eliminate these two issues, we simply put a glass lens in our camera. The lens then gathers waaaaaay more light than that little pinhole and sharply focuses that light into a picture on our film. The lens is really the most important part of your camera. If you're using a compact camera that has it's own non-removable lens, you may want to consider upgrading in the future to a camera that lets you change lenses. A good, sharp lens will be a huge asset to you in your photography as you become more and more concerned about the quality of your images. Lens quality is a much more complex issue than you might think at first. A really good, sharp lens uses special glass - several layers of different kinds of optical glass that have been precisely ground and then inserted into a mechanism that you can move around to focus all of those layers on your subject. Good lenses are spendy, but they will be well worth it if you're interested in producing the best possible photographs. Choosing a camera lens would be easy if all you had to worry about was getting a good quality lens, but the many different variables - focal lengths, zoom lenses, lens "speed" - complicate the choice. We'll go over some of the aspects of camera lenses and how those should influence your decision when you're trying to find the right lens for what you want to do with your camera. If you do have an interchangeable lens camera, the camera will most oftentimes come with what's considered a "normal" lens - a 50 mm lens. That focal length lens is regarded as "normal" because the image it makes is very close to what the human eye sees. This is a great place to start. I recommend using that sort of lens until you're very familiar with it and comfortable using it and start to feel the need for a lens that is suited for some area of photography that you're particularly interested in. Let's do a quick overview of different focal lengths of lenses and their common uses. |
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 The wider the angle of your lens, the more linear distortion you'll have in your image. You can see what I mean by linear distortion in this image.Notice in this photo of the aftermath of a forest fire the way that the ground seems to almost "bubble". The wider lens you use, the more apparent that will become. Sort of like looking into one of those convex mirrors you see in the corners of convenience stores and such - it also will make things seem out of proportion, in that the closer an object is to the lens, the larger it will seem. A good example of this is a close up photograph of a person or animal using a wide-angle lens - their nose will appear very large in proportion to the rest of their face, creating a comical effect. Those kinds of photos have been a big hit in the greeting card industry as of late. This can also be used very effectively in landscapes to draw attention to the foreground of an image and add depth to the overall image. |
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This image showcases the rocks in the foreground, drawing the viewer in and giving them the feeling that they are "right there". Wide-angle lenses are a must for landscape photography, so if your interests lie there, you might want to consider adding one of these lenses to your inventory.Another unusual effect that wide-angle lenses tend to create is the problem of converging vertical lines. This effect is most noticeable when taking a photograph of a building from a low angle, looking up. In the following photograph, notice how the building's lines curve in towards the top. |
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| Notice the curving bottom line, also. A full fisheye lens actually makes a photograph that is circular in nature. A fun lens to use, but probably not the first on your list of lenses that you need. | ||||||||
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Long-Focus Lenses Long-focus lenses are basically the opposite of wide-angle lenses. The term is used for almost all lenses that are longer than "normal" focal length. They're also oftentimes referred to as "telephoto lenses". When discussing focal length in the last lesson, I made a general statement that the number of the focal length is generally how many millimeters it is from the front of the camera to the film plane inside of the camera. If you happen to have a 400 mm lens lying around and decide to whip out your ruler and measure it, however, you'll probably notice that it is not 400 mm long. That's because inside of the lens barrel they use elements that magnify the image. A lens that is actually shorter than its focal length is technically called a telephoto lens. If your 400 mm lens actually happens to be 400 mm long, you've got a long-focus lens that is not a telephoto, even though they're all commonly called telephoto lenses. That's just a bit of trivia for you. I'll use the terms interchangeably in this section, but now you know the difference. So what are telephoto lenses used for? Let's look at the following example of the same scene taken from the exact same spot, using both a wide-angle lens and a telephoto lens: |
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Another thing that telephoto lenses are good for is eliminating those converging vertical lines that I mentioned when talking about wide-angle lenses.This shot was taken from quite a distance using a telephoto lens. Notice that the lines of the building don't seem to curve like the old brick schoolhouse in the previous example. If you can keep your lens and film plane parallel to the surface you're shooting, you'll have good luck with eliminating those converging verticals. They also make special lenses called Perspective Control (or PC) lenses that can help you correct this problem if you can't get far enough away to use your telephoto - unless you are planning on doing a lot of architectural photography, though, I wouldn't recommend one of these. They're rather expensive. There are a few disadvantages to buying telephoto lenses, so unless this is the type of photography you're really interested in, I wouldn't recommend one. Long-focus lenses can be very expensive - when you take a picture at a great distance like the telephoto example of the barn above, you tend to get a bit of haze to your image. Only the purest environment will eliminate this. They're also very bulky, and yes - expensive. A 200 mm telephoto will probably take care of most of your needs, unless you're planning on photographing something small, like birds, from a great distance. You can also enhance your telephoto lens with something called a "tele-extender". It is another lens that you put on your camera, and then your regular lens attaches to the front of it. A 2x tele-extender will double the size of your image. They're reasonably inexpensive, not huge and bulky, and give you a lot of versatility. Their disadvantages: you won't get quite as sharp of an image using a tele-extender, and you'll have to open up your camera by 2 stops with a 2x tele-extender because they decrease the amount of light that comes into your camera. But if all you have is a 200 mm lens and that rare African Ruby Throated Ring Necked Swallowtail shows up, you can throw on a 2x tele-extender and increase your lens power to 400 mm. They even make them in 3x and a few other variations. |
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Portrait Lenses Lenses that are between 85 mm and 135 mm are called "portrait lenses". Remember how we talked about wide angle noses causing the "big nose" effect? This is called perspective distortion, and here's an example of that, along with a portrait taken using a 110 mm lens, which is what I generally like to shoot portraits with. |
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| These are both self-portraits. Notice the caricature feeling of the shot taken with the wide-angle lens and the more in-proportion feeling of the nose in the standard portrait. If this is an area of photography you're interested in, this might be one of the first lens purchases to put on your list. I find a focal length of right around 100 mm to 110 mm to be very flattering in portraiture. You'll be able to get close enough to fill your entire frame with your subject while still standing a reasonable distance from them, too. | ||||||||
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Macro Lenses A macro lens is used to take pictures very close up of objects. A true macro lens will make an image on the film that is exactly the same size as the subject. They're commonly used to photograph flowers, insects, coins, etc. I do a lot of macro photography and it's one lens that I couldn't live without. Macro lenses can come in any focal length - 24 mm, 50 mm, even 200 mm. In addition to being able to function as standard lenses, they will also focus much closer than regular lenses have the ability to do. The following images were taken with macro lenses: |
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Zoom Lenses There are also zoom lenses. These will let you change the focal length that you are using without changing lenses. They tend to be expensive, and because of all of the mechanical stuff inside the lens barrel that allows you to zoom in and out, the optics tend to not be quite as sharp as a fixed-focal length lens. However, some of them aren't too bad and they can be very handy if you're out shooting and want the versatility of more than one lens without the hassle of carrying various lenses around with you. |
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Aperture and Depth Of Field In the last lesson we talked about aperture and shutter speed and how they affect your photograph's exposure. Aperture also controls something called depth of field. When you focus your lens on a subject, anything at that same distance will similarly be in focus. Things that are closer to or further from the camera lens will gradually - or drastically - be less sharp. Your camera's aperture controls how large of a zone is acceptably in focus. This is called "depth of field", and the smaller your camera's aperture, the larger that depth of field zone is. |
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In this image, the tip of the red pencil is sharply in focus and the acceptable focus zone fades quickly so that the other pencils are more and more blurry. This was achieved by using a large camera aperture. Depth of field also increases with distance. The farther you place the camera from your subject, the more of the subject you can get in focus. Landscapes tend to have deep depth of field, while macros have a very shallow depth of field because the subject is so close to the lens.
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| Shallow depth of field can be used in many interesting ways for impact in your photographs. Here are two more photographs of the same subject using different depths of field to create different effects: | ||||||||
 
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Finally, don't take this to mean that stopping down your aperture and throwing your focus on infinity will give you a completely in-focus landscape photograph. We've talked about shallow depth of field, but when you want deep depth of field in a landscape image, you should use something called "hyperfocal distance". If you go back and refer to the lake image used earlier in the lesson where I noted the rocks in the foreground, that sharp focus throughout the image was achieved using this method. It's the best way to assure your foreground is tack sharp as well as the rest of the photo. First, you need a lens with a depth-of-field scale imprinted on it. A lot of lenses don't have this on them, so if you're selecting a lens to buy, this is a good thing to look for. It's a bunch of numbers written on the lens that coincide with the apertures on the lens. Each number is printed twice - once on the left of the center position, once on the right. If your lens has apertures running from f/2.8 through f/32, you will see a "2.8" written in the center and a "32" printed way to the left and then again way to the right. I know, you're saying, "Man, all those little numbers look so CONFUSING! What the heck am I supposed to do with those?" It's not as hard as it looks, and I promise you'll be happy you learned this. This is what you do: Set your lens to its smallest possible aperture. That's f/32 on the fictional camera I'm talking about, so we'll stick with that. So now find the "32" markings on the depth-of-field scale on the lens. Got ‘em? Okay, now instead of the normal procedure of positioning the infinity distance mark at the center, position the infinity symbol above the "32" mark on the right. Now you are now focusing most sharply on a distance of somewhere around ten feet or so, but infinity is just within your depth of field, also sharp. Okay, now look at the left-hand marking that says "32" and it will tell you at what distance your depth of field starts - from about three or four feet out all the way to infinity. |
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Tripods Okay, if I don't get around to talking about tripods soon it's going to drive me crazy, so I guess this is as good of a place as any, and it sort of fits in with the lesson on lenses. Personally, I do my best to never - ever - take a photograph without using a tripod. There are some circumstances where it's just not practical, but they are few and far between. Using a tripod will make a big difference in your technical quality of your pictures. That being said, there's sort of an informal rule that says it's okay to hand-hold a camera if your shutter speed is at least equal to your focal length. Huh? Easier way to say it - if you're using a 100 mm lens, you should not hand-hold your camera at less than 1/100 second. A 500 mm telephoto lens should not be hand held at less than 1/500 second. Even if you are positive you have the steadiest hands in the world and you really don't need a tripod - trust me - you do. Why am I so emphatic about this? The absolute worst mistake a beginning photographer can make is to not use a tripod. I've seen some beautiful shots that have been worthless when viewed up closely because of camera shake due to not using a tripod. I went through a stage where I thought they weren't REALLY necessary, too, and had a good portion of my best early images ruined due to this. So what should you look for in a tripod? Several things.
I can't stress enough what a help this will be to improving your image quality. There are also monopods on the market if you're hiking and a tripod is too much to carry. |
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