Monday, March 24, 2008

Comment for Inside the Mind of Mar's blog entry "Creationism is incredibly interesting".

I couldn't post the Youtube URL in the comments section so I'll embed the video on my blog.

Lewis Black sums up my views on Creationism pretty well.

Tuesday, March 11, 2008

Digital Photography 101 (part 2)

Choosing the Right Camera
Some people say the camera is only as good as the person using it. Although that may have been true in the days of manual film cameras, the amount of new technology crammed into modern digital cameras helps even mediocre photographers look like pros. Unfortunately, technology can't break the laws of physics yet, so you still need to understand what physical limitations your camera has.

Function over Form
Go to any big box electronic retail store and ask the sales guy what's the most important feature customers are looking for in a camera and they will say that it's the style and look of the camera not the kind of picture it produces. Since we are all price conscious consumers, this has led manufacturers to make two types of cameras: stylish cameras that take bad pictures, and ugly cameras that take stylish pictures. Therefore, chances are, if your camera comes in four designer colors like in the picture to the right, it's probably time to be shopping for a new camera.

Compactness Has its Usefulness
I'm not saying that you should be throwing away your compact, portable cameras. Often times, their portability means you can always have them around to take shot whenever you see something interesting. Also these small cameras are often inexpensive, making them suitable for places where your more expensive equipment might get damaged or stolen. Since almost everyone has one of these cameras nowadays, I won't go into them any further.

Fixed Lens vs DSLR
High performance cameras fall into two main groups: Fixed lens (or standard digital camera) or DSLR (Digital Single Lens Reflex). As you can guess the biggest difference between these two is that DSLR's are designed with interchangeable lenses in mind. Your fixed lens camera should have a decent optical zoom range and aperture size. Most "prosumer" models have attachments that go over the fixed lens to increase the zoom or increase the field of view however if you are planning to go that route it would be better to jump directly to the DSLR since any lens you buy is likely to remain compatible with the cameras you buy in the future (provided you stay with the same camera company).

Must Have Features
  • Manual shutter speed, aperture, ISO control - Lets you control the exposure. Be sure that there is a way to manually set all of these at the same time.
  • Little or no shutter lag - Shutter lag is the time between when you press the button to take a shot and when the camera actually takes the shot. Anything that takes longer than a split second on a sunny day is too long in my book.
  • A low noise/high ISO capable sensor is a big help in low light situations when you need a higher shutter speed
  • A Shutter timer lets you press the shutter button, but the camera wont take the shot until a few seconds have passed. This is invaluable for taking those long exposure shots where the shake from pressing the button will cause motion blur.
  • RAW file format - If you're willing to deal with larger image files and post-processing software, then being able to shoot in the camera's "raw" format (instead of Jpeg) is the only way to go. Raw formats usually contain much more image data especially in the dynamic range, allowing you to recover hidden detail even with a badly exposed image.
  • Adjustable autofocus points and/or manual focus - Often times what you want to focus on isn't exactly in the middle of the shot.
Nice to Haves
  • Hot shoe for flash - if you need a flash, you must use an external flash simply because no built-in flash can provide even diffuse lighting if its shining straight at the subject inline with the camera.
  • White Balance metering - Not necessary if you shoot in raw, but if you're not, then this will ensure that your images show up with the right colors.
  • Image Stabilization - This will allow you to take some shots that you couldn't without a tripod. It only helps if you are moving, not so much if the subject is moving. On DSLR's this is sometimes implemented in the body and other times its in the lens.
Since the price of entry level DSLR's have been plummetting I will recommend that you get a DSLR if at all possible. There's really no substitute to the flexibility of attaching different lenses to your camera. Plus there is no single lens that is good at everything so its unlikely that the lens on a fixed camera will suffice for all your needs. In my next article I'll delve more into the specifics of shopping for a DSLR so you can make an informed decision.

Digital Photography 101 (Part 1)
Ever since the advent of the first digital camera, photography has experienced an explosion of growth. Nowadays, its hard to even find a cell phone without a camera. Unfortunately, the ability to take limitless shots without wasting any film and the ubiquitousness of the digital camera has not done anything to improve the quality of the pictures we take. I'd like to change that.
Taking good photos is not difficult. You don't need an expensive equipment, and once you get it you may find photography to be a fun and rewarding hobby.

Camera Operation
Cameras work by allowing light to come through the lense which focuses it onto some sort of sensor (or film for traditional cameras). The light is only exposed to the sensor for a very brief amount of time. That light will cause the sensor to create all sorts of electrical signals representing the image that the camera sees at that point in time. The camera's internal computer will then convert those signals into a digital image file on your memory stick. I've glossed over several details here, but this is the general idea and it will serve as the basis for the rest of the article.

The Basics of Exposure
Exposure is all about how we get the light from the scene you are photographing, to the camera's sensor. Most digital cameras allow you to modify 3 basic components for controlling your exposure. Understanding how these components affect your exposure will help you keep most of your photos out of the recycle bin.

1. Lenses
When light enters the lens, the light gets focused onto our camera sensor. Just like how your eye glasses can have different strengths, camera lenses have different strengths too. To measure this we use the term focal length. Focal length is measured in millimeters (mm). If you want to shoot something far away, you will want a lense with a large focal length (ex. 800mm). These are called telephoto lenses. If you want to shoot something thats really huge and you don't want to step back so much to get everything in the shot, you'll want a small focal length (eg, 17mm) these are often called wide-angle lenses. An easy way to remember this is to imagine that all the light that enters the lens is in the shape of a cone and the focal length controls the height of this cone. Smaller focal length means you have a short cone with a shallow slope so the light cone casts a wide view (ie wide angle lens). Larger focal length means a steep cone so things far away seem bigger (ie telephoto lens). When you zoom in or out you are changing the focal length of the lense. As you can imagine, a larger cone allows more light in which will change your exposure. Conversely, a telephoto lens allows less light to enter, however that is not the only issue. With telephoto lenses, the image magnification, also causes angular camera motions to be magnified. That is, as you zoom in, any movement in the hands holding the camera will be magnified in the photo.
Usually the scene you are trying to capture will dictate what lens or focal length you will use. However, sometimes if you cannot get enough light or you cannot hold your camera steady enough, it might be better to use a lower focal length and resize the image in post processing later.

2. Aperture
Besides, focal length, the next most important aspect of a lense is how much light it can let in. Usually the light that enters at the edges of a lense gets distorted so camera lenses limit that light with an O-shaped disk placed between the lenses. The hole in this disk is called the aperture and can be enlarged or reduced by the camera or by rotating a ring on the lens itself. A bigger hole lets more light in but with a more narrow depth of field (which we'll get into later). Aperture is measured in f-values (ex. f/22 or f22) . The lower the f-value, the bigger the aperture so f/22 has a much smaller hole than f/1.4.
When buying a lens or a camera with a lens you will probably see it listed like this: 18-55mm F/3.5-5.6.
The first part means that the focal length can vary between 18mm and 55mm, but the second part doesn't mean the aperture can be from f3.5 to f5.6. It means that the largest aperture can vary between f/3.5-f/5.6. Most lenses can easily produce small apertures f/30+. The hard part is keeping the apertures large throughout the range of focal lengths. That's why the largest aperture that you can use will shrink when you zoom in.
Depth of field is the range of distances from the camera where things will be in focus. Lets say you wanted to take some landscape photos. You would probably like the wildlife in the foreground and the mountains in the background to both be in focus. In this case you want to have a wide depth of field. On the other hand, suppose you wanted to emphasize the subject of the photo, you could use a large aperture to create a shallow depth of field so that only the subject of the photo is in focus. The photo to the left is my baby Sophia sleeping next to her mom. Notice how Sophia is in focus while my wife isn't. This was shot with an aperture of f/2.8.

2. Shutter Speed
Shutter speed is the amount of time that the aperture will remain open so that light from the scene can reach the camera's sensor. This is measured in seconds or fractions of a sec like 1/30. Since most photos are taken with shutter speeds like 1/20, 1/30, 1/100, etc, your camera may show only the denominator of the fractional part like so 1/20 is shown as 20, 1/30 as 30 and 1/100 as 100. Long shutter speeds like over 1 second, will usually be displayed with a double quotation mark, like 2".
The combination of shutter speed and aperture determines how much light gets to the sensor, i.e. the exposure. For example, if you let light through a large aperture for a short time, you can still get the same exposure by letting light through a small aperture for a longer time. The biggest drawback to a long exposure is that the camera and the scene has to be perfectly still during the entire time that the shutter is open, otherwise your photo will be blurry. This type of blur is known as motion blur. In the photo on the right, you can see how the the people who were moving look kinda ghostly while everything else is pretty sharp. The woman in the center remained almost perfectly still during the shot so she had almost no motion blur. This was a 2 second shot (shutter speed) at f/8.

3. ISO Sensitivity
Also known as the ISO speed, the ISO sensitivity of the camera's sensor is the third and final component of determining a photo's exposure. Camera sensors usually have the ability for you to increase or decrease its sensitivity. You can think of this like the volume knob on your car radio. If you get a weak signal, you can up the volume, but the more you turn the knob, the more noise you will get. ISO sensitivity works the same way. The higher the sensitivity, the less light you will need, but at the cost of more noise in your photo. Ideally, you want to use the smallest ISO possible for the aperture and shutter speed that gives you good results. Often times the lowest shutter speed that minimizes your motion blur is the driving factor for the ISO you use. Its usually easier to correct ISO noise in post processing than motion blur.