First lets distinguish two types of camera sensors that we have available (most common ones). You may have heard the term "Full Frame" and "Crop" sensors. If you didn't, it's ok, I will not hold it against you. Why am I talking about sensors instead of lenses? Just like with the camera situation, you would rather say "Just point to the right lens" or "Go buy it for me" but no! You will learn and decide for yourself. I'm not going to bore you to death but you have to know a few things.
The very elaborate and the most important component of any digital camera is the sensor. It is the heart of the camera and it is what interprets light captured into a photograph. Before digital, there were 35mm film cameras so without going into details, a full frame is the exact equivalent of a 35mm frame and a crop sensor is 3/4 or other fraction of the full frame. That's basically it, not too complicated. You might ask yourself why would manufacturers make a 3/4 frame? Well it's about twenty times cheaper to make which makes it the dominant sensor on low end cameras. Pro cameras have full frame sensor and this is one of the reasons they are more expensive. Full frame receives much more information and can use a higher ISO setting without too much "noise".
So what does it have to do with lenses? Well pretty much everything. Lets say we have a wide-angle lens and we put it on a camera with a 3/4 sensor. Take a shot and you will get a normal wide-angle photo:
|17-40mm lens on a Canon Rebel XTI at 17mm|
|17-40mm on a Canon 5D Mark II at 17mm|
Just like with cameras and anything else you buy, there are good lenses and there are "can't afford so I bought this one instead" lenses. It's pretty simple really; more expensive lens will produce the sharpest and the better quality results than the less expensive. High-end lenses will be more weather resistant, will be made in most cases out of metal instead of plastic and most importantly, the glass will be much better. I can't emphasize enough how important it is to have a good lens. When you do decide to go with a more professional equipment, start saving for the camera and at least one good lens. In a Canon world, a good lens is very easily distinguished by the thin red line around the lens. This is a sign for an "L" lens or a "Luxury" lens. When I got my first "L" lens, it was one of the happiest moments of my life (yes it's sad but I like a good lens so don't judge me)! Prices for the "L" series range from $700 to about $10,000 (yes people pay that much for a lens). So what is the difference between the lenses?
|Canon's array of glass|
This is the range at which the lens will capture light. For example: 17-40mm is a wide-angle lens, 24-70mm is mid-range zoom and a 70-200mm is a zoom lens capable of capturing close-ups without getting too close to your subject. By the way, those three lenses are the most common lenses in a wedding photographer's bag. They cover pretty much all the focal length you will need so you don't have to worry about missing the action. Other than weddings and events the most common uses for a wide angle lens can be landscape or architecture photography. A mid-range zoom lens is a great all purpose lens that can be used for travel (when you don't want to carry more than one lens), portraits, fashion and numerous other uses. A long zoom lens most often will be used for portraits, sports or nature photography.
There are lenses that have a set focal length such as 50mm, 85mm, 100mm and other lengths. These lenses are called prime lenses. In most cases they will be much more expensive and thus much faster (I'm getting to lens "speed" soon). In fact my next lens will probably be 85mm or 100mm "L" lens. The quality is superb but unfortunately the price is around $2,000 so it is not a purchase you make without much consideration. Some photographers use only prime lenses because they believe it produces the best photos and they call it laziness when you use a zoom lens in order to avoid moving your butt closer to the subject. With a set focal length you will need to move much more to get the results you want, when with a zoom lens you can just zoom in without moving. A small tip that I learned a while back: Try using the "wrong" lens for a specific situation. For instance: shoot a portrait with a wide angle to include the subjects' surroundings or shoot a landscape with a long zoom to single out a great feature instead of trying and capture it all:
|Shot with 70-200mm at 200mm|
If you have a DSLR lens, take a look at the numbers written next to the focal length. It should say something like 1:3.5-5.6 or 1:4 or 1:2.8 and so on. Well this my friends is the number we all want to see as low as possible and we are willing to pay a lot of money for. This is the f-stop number. I won't go into how does this work but the most important thing you need to know is the lower the number the wider your lens will open to accept more light in a dim situation. In photography, much like in other aspects of life, something is gotta give. There are always trade-offs for the three most important components: f-stop, shutter speed and ISO. Shutter speed number is usually shown in fractions such as 1/125 or 1/60 of a second. The FASTER the shutter opens, the less light will go through but you will be able to freeze the scene. However, there is a trade-off. Less light comes in, the darker the photo will come out. This is where the f-stop comes in. The lower the number (f2.8, f2...) the WIDER it opens, which will allow more light to come in despite the high speed of the shutter. Light will come fast but there will be more of it. So lets take a scenario where you want to take a photo of your child during bath-time in the evening (based on real events :) ). You need to consider a few things: The shutter speed must be pretty fast - 1/125 because the child moves all the time. The Aperture (the hole that opens for light and is measured in f-stops) must be low because it is pretty dark in your bath (for the camera at least), so preferably it will be f-2.8 - this is by the way where you start to understand that you need that faster and more expensive lens that can go as low as 2.8 and not 3.5 or 5.6... Also, it would be great if your ISO setting would be high (around 1600-2000) and this is where you want that expensive full frame camera that can handle this high ISO setting without showing signs of noise. So let's say you spend about $5,000 for equipment and took that shot at 1/125, f-2.8, ISO 1600. You should have a great shot of your child that doesn't really care about the money you spent to get it...
|24-70mm L 1/125 f-2.8 ISO 1600 at 70mm|
So the bottom line is this: A god lens is important just as much as the camera you get. When you buy a lens, try to get one with a low f-stop and a focal length you will use more often. My favorite is 24-70mm L f-2.8 zoom lens (about $1,300) and I use it pretty much for everything. I can't really recommend a cheaper lens because I would be lying if I say I enjoyed my first kit lens that came with my camera ( 18-55 1:3.5-5.6) but believe it or not, I shot a wedding with it and got pretty damn good photos. So although I can't say get the cheaper one, it's not the end of the world if you do and save money for a great buy in the future. There are much more that could be said about lenses but i think that i covered the basics and hope it helped.
Next post will be about creative composition and should be pretty fun.