Photography 3-Bits ================== Ben Collins-Sussman (sussman@red-bean.com), September 2011 OK, here's the basic idea behind "taking pictures" vs. "making pictures". Like many things, photography is a delicate balance between science and art. You need to master both to succeed. * Science: if you don't learn the science/technical side, then you'll have no control over what you get. Having "artistic vision" is nice, but then half the time you end up being surprised at what your camera gives you. No picture you ever take should be too dark, too light, blurry, or any other thing you weren't expecting. You shouldn't be relying on luck. You should always be in control of what you create. No surprises. * Art: if you refuse to learn the artistic side, then you end up creating making mechanical, uninspiring things based on boring variables. Learn the rules of composition; figure out what feeling you're trying to convey; be deliberate in your artistic choices. Learn to break the artistic rules when it feels right. Most people already have glimmerings of artistic sensibility -- it's why they're drawn to photography in the first place. This is my quick essay on the technical basics. Learn these basics, and then you'll have a nice balance of art and science at your fingertips. EXPOSURE 'Exposure' is how long the light hits your sensor. If it hits for too long, your picture is overexposed and blown out; if it's too short, your picture is underexposed and too dark. It would seem, then, that one should simply let the camera determine the optimal exposure, right? Absolutely. Cameras can make pretty good guesses most of the time -- that's what 'automatic' modes on cameras do. But we don't want to rely on guesses. We want to be in control. THE PROBLEM, is that there are 3 variables that control the exposure, which means there are a near-infinite number of ways to get "correct" exposure, and the end-results all look different. The three varibles are: 1. ISO 2. Aperture 3. Shutter speed ISO: ISO refers to how sensitive your sensor is to light. It comes from the old days of film -- "ISO 200" was best for outdoors, whereas "ISO 400" was twice as sensitive and better for indoors. Nowadays, digital cameras emulate light sensitivity on the same scale. ISO ranges from 100 up into the thousands. On a practical level: 100-400 is best for sunny outdoors. 400-1200 is best for indoors. 1600 and up is for very low-light situations. The danger of increasing ISO is that the picture gets *more grainy* as it's turned up. You start to see weird artifacts in the pictures. That's the tradeoff: in return for working in darker situations, you start to lose picture quality. APERTURE: Aperture is how big the hole is in the lens. The bigger the hole, the more light gets in. Aperture is measured in units called "F stop", and written as "f/8". The smaller the f-stop number, the wider the hole. Each lens has its own intrinsic aperture range. f/1 - 2: super big hole f/3.5 - 5.6: pretty big hole f/5.6 - 8: the 'sweet spot' for most lenses, where things usually look best. f/8 - 11: somewhat small hole f/11 - 22: approaching pinhole sized Why does aperture matter? Because the bigger the hole, the shorter the depth-of-field. Depth-of-field is how much of the picture is in focus. If absolutely everything is in sharp focus (foreground subject, background), then it's a "high depth of field". If only a tiny bit of the subject is sharp and everything else is blurry, then it's a "shallow depth of field". Artists like to mess with aperture directly, because depth-of-field is an artistic choice. For example, a portrait with the background blurred feels very different than a portrait where you can see every detail behind the person. For a blurry background, you'd choose f/2. For a sharp background, you'd choose f/16. Lenses with big apertures cost a lot of money, because they allow you to work in lower light, and give you bigger choice in depth-of-field (artistic choice, that is.) SHUTTER SPEED: How fast the hole opens and closes to expose the sensor. Assuming the ISO is held constant, shutter speed and aperture "trade off". If the aperture is huge, then the shutter speed needs to be really quick to avoid overexposing. If the aperture is tiny, the shutter speed needs to be long to avoid underexposing. Changing one variable automatically changes the other. Shutter speed is measured in fractions of a second. The main effect shutter speed has is on blur. For a handheld shot, humans generally need the shutter speed to be 1/80th of a second (or faster) to avoid the whole picture being blurry from shaky-hands. If you use a tripod, this restriction is removed. Of course, this doesn't stop the subject from moving. :-) Then again, maybe you *want* the subject to be blurred as an artistic choice. PUTTING IT ALL TOGETHER: The basic algorithm of the clueful photographer is this: 1. Set the ISO based on your environment, understanding the tradeoff between 'being able to work in the dark' and 'picture quality'. 2. Put the camera into 'aperture priority' mode (usually the letter "A" on the dial). This means you choose the aperture, and the camera sets the shutter speed appropriately. 3. Before making a photo, set the aperture to something you want. In other words, make a deliberate choice about depth-of-field. --> Make sure the proposed shutter-speed is reasonable, and won't create a blurry/shaky photo. If so, you'll need to increase the ISO sensitivity. 4. Shoot photo. Of course, in a given situation you may decide that subject blur is more important to you than depth-of-field. In that case, set the camera to "shutter priority mode" (usually letter "S" or "T" on the dial) and repeat the algorithm -- this time you get to set the shutter speed, and decide if the proposed aperture is acceptable. If you're really hard-core, you can put the camera in full manual mode ("M" on the dial), where you get to choose all 3 variables. The camera will warn you if your over- or under-exposing, but it's your own artistic choice to make. FOCAL LENGTH The last variable to learn has nothing to do with exposure. It has to do with the "zoom factor" of a lens. When you look at a scene, how much of it gets framed by the camera? The classic camera lens uses a focal length of 50mm... because it's closest to the amount of scene that a human eye sees. It's considered the most natural. Focal lengths that are bigger (100mm, 200mm, ...) are "zoomy", in that far-away things fill up the whole frame, and smaller focal lengths (28mm, 18mm, ...) are considered "wide angle". Wide-angle is fun for outside panoramic shots, but beware that things start to get curvy and warped like a fishbowl. You may not notice in shooting landscapes, but indoors it will make rooms looked warped. And if you take a portrait with a focal length less than 50mm, it's extremely unflattering -- it makes the face look warped and wide. Zoom lenses are fun too, because it allows us to be lazy and not get too close to the subject. They're also flattering in portraits, as they have the opposite effect of the fishbowl -- they tend to "flatten" things out. The effect is incredibly flattering for portraits. The ideal focal length for portraits is often considered 80mm, but models on magazine covers are often shot with 200mm or 300mm lenses, with the photographer standing 50 feet away! --> Rule of thumb about shutter-speed and focal length "If the focal length is N, then the shutter-speed needs to be at least 1/N fast to avoid hand-shake." In other words, for a 50mm lens, use a shutter speed of at least 1/50th. If you're using a 200m zoom lens on something far away, you need a shutter speed of at least 1/200th to avoid blur. EQUIPMENT So why do photographers like huge cameras (SLRs) with interchangeable lenses, as opposed to point-n-shoot pocketable cameras? 1. SLRs give you full control over all variables. 2. SLRs let you choose the best lens for the situation. 3. SLRs have huge sensors and use big lenses. The bigger the sensor and bigger the lens, the better the picture quality. This is a fact of physics. For example, no matter how great the software is on your mobile phone (or how many 'megapixels' it has), the pictures will always look like crap... it's a pinhole lens and tiny sensor. SENSOR SIZE Once upon a time, 35mm film was the professional standard. All focal lengths are interpreted against this standard. In other words, a 50mm lens' framing ability is judged by the way it projects light onto a 35mm rectangle of film. It turns out that making digital sensors (CCDs and the like) is insanely expensive, and thus a majority of digital cameras have light sensors that are considerably smaller than a 35mm piece of film. No problem, except that this means that a 50mm lens no longer gives the same look when projected onto a smaller sensor. The smaller sensor only picks up the cropped center of the image, creating an "effective zoom". It's not really zooming on anything, but because you only see the center part of the projection, its as *if* you were using a zoom-ier lens. Most digital SLRs have what they call 'crop sensors'. They have a 1.6x zoom factor. In other words, if you attach a 50mm to crop-sensor camera, it actually behaves like an 80mm lens. If you're loaded with cash, you can spend $2-3k on a camera with a 'full frame' sensor -- one which is actually the size of a piece of 35mm film. Lens focal lengths will then be true. (The image quality is much nicer as well.) On the other hand, if you go with a regular crop-sensor camera, I'd recommend buying a 30mm lens, since the result will be about 50mm. WHICH SLR SHOULD I BUY? Here's what I tell everyone about buying an SLR: 1. Canon and Nikon own 95% of the market, split it evenly, and have essentially identical products up and down the line. Neither is better or worse. Figure out which of your buddies are into photography, and whether they're Canon or Nikon people. Buy whatever brand they use, since Canon lenses only work on Canon bodies, and Nikon lenses only work on Nikon bodies. Then you'll always be able to test out, trade, swap lenses with your friends. It's a big deal... photography is a social hobby. If you buy something other than Canon or Nikon, you'll forever be in an isolated minority. 2. Specific DSLR camera bodies aren't that important. Bodies range from $600 to $2000, but the differences aren't that interesting. They're all greater than 10 megapixel resolution, and 10 vs 12 vs 18 vs 22 megapixel is completely meaningless -- they're all able to create wall-sized posters. :-) When you buy a high-end camera body, you're paying for a nicer UI (bigger rear screen, nicer controls, etc) as well as a bigger light sensor. The bigger sensor, the clearer the image. But the quality difference between a "crop sensor" (what most DSLRs have) and a "full frame sensor" (actually the size of a 35mm piece of film) definitely isn't worth the $1500 difference. Better to put your money into a lens. 3. Lenses are *everything*. By buying a $400 lens (instead of using the cheap $80 lens that comes with most SLRs), the difference in picture quality is just staggering. If you jump up to a $1200 lens, the quality really does jump by 3-5x. My recommendation to beginners: buy an inexpensive DSLR body (maybe even last year's model, used off ebay). Put all your money into a high-end lens. You'll be delighted.