Presentation on theme: "Using Digital Cameras And Image Processing Software."— Presentation transcript:
Using Digital Cameras And Image Processing Software
Today, digital cameras have become affordable and useful devices that have become part of nearly everyone’s life. Unlike they cameras of the past they give you immediate feedback to you and possibly your subject. No matter what camera you have, you will be able to use it in creative and rewarding ways.
All digital cameras have a power switch and they are usually designed so the camera doesn’t accidentally get turned on or off while you are trying to take a picture. Also, if you don’t use your camera for a specific length of time most of them have a feature which turns the camera off automatically after a minute or so to conserve battery life. Of course, all of the pictures that you have previously taken are stored in a memory area on the camera, so you won’t lose them whenever it is turned off.
You will need batteries for your digital camera, usually AA batteries or a lithium battery. It is a good idea to buy rechargeable batteries for it as replacement can get expensive over time. Good re-chargeable batteries can last up to 3 hours and usually last for several years before needing replacement.
Your camera should have a switch that lets you move between picture-taking mode and viewing mode for the ones you have already taken. The actual icons or words will vary on each camera, but the concept is the same. It is a good idea to first check your user manual for an overview.
When you turn your camera on and select picture-taking mode, you will be able to take a picture. Some cameras don’t have LCD displays and so, to view the picture you are about to take, you will have to use the viewfinder (like a regular camera). If the camera has an LCD display, you will be able to see what the lens is seeing on the LCD display. If you can’t see anything, check to make sure you have removed the lens cap! LCD displays are expensive and take a lot of battery power, so many cameras don’t have them in order for the camera to be more affordable and energy efficient.
If you are looking to save battery power, try turning off the LCD display instead of the camera. Many cameras have an LCD Display on and off or a backlight on and off to help you do this quickly. Here is a nice trick for cleaning your LCD display. Instead of using a lens cloth, try using a couple of pieces of scotch tape. Place the tape over the LCD and lightly press it completely on the LCD. When you pull it off, the fingerprints will come off with the tape!
Most digital camera shutters work like a regular auto-focus camera. For some, if you press it half-way down, it will focus on the object in the center of the image. Then, to take a picture, you need to press all the way down, past this point of focus. Most cameras will either flash the word “recording” on the LCD display or the LCD display will “go black” or turn off for a second while the image is recording.
Many cameras will also let you choose exactly what focus or focal distance (the distance between the camera lens and the object in focus) for your picture. For example, the camera could be set to a focal distance of 4 meters. Your camera will focus at 4 meters distance, no matter what is in the center of the image.
Your camera may also also have a macro feature. This is often designated by a flower with the appearance of a tulip. With the macro feature you can get the camera to focus on an object that is EXTREMELY close to the lens. With this feature you can set your zoom all the way to wide angle and focus on the detail in small objects--flowers, insects, etc.
Digital cameras usually have a flash feature like regular cameras. Often this is displayed as a lightning bolt. If you press the flash icon, you will see this lightning bolt appear on your LCD display and means that your flash is set to ALWAYS go off regardless of lighting. If you press the flash button again, you will see a “no” symbol around the flash. This means that the flash is set to NEVER go off. If neither symbol appears, but the flash light is on, the camera is set to use the flash if it deems the need exists.
Some digital cameras also have a red eye reduction setting so that the flash will go off slightly before the shutter snaps the picture in order to reduce “red eye” effect.
Zoom The ability to zoom is a feature found on most digital cameras. You may see a slider or button with the letter W (wide angle) and T (telephoto) at the other end to zoom in and out. Many digital cameras have both an optical and digital zoom. An optical zoom actually uses a combination of lenses (as with binoculars) to make the image appear closer with no loss in image quality.
Unlike an optical zoom, a digital zoom magnifies the pixels that make up the image. Using a digital editing program like PhotoShop on the computer, you know that the closer you zoom in the larger the pixels become and the image becomes less clear. This is analogous to using a digital zoom on your camera where you also experience a significant loss in image quality. Some digital cameras may have a line on the LCD display to divide optical and digital zoom features.
No Optical Zoom Ok for very casual snapshots around the house, or where you can physically get closer to your subject(s) if you need to. Since most cameras today have some sort of optical zoom, most likely your sub-$150 models will fit into this category.
2X - 3X Optical Zoom Many if not most digital cameras fall into this zoom range. Good for casual snapshots, family outings, and general vacation shots where scenic distant shots are not that important.
4X - 6X Optical Zoom Better choice for distant landscapes. Better for trips to the Zoo, amateur sporting events (kids soccer, etc.).
7X - 12X Optical Zoom An excellent zoom range for pro sports photos, distant landscape or vacation shots, and wildlife photography, too. A few manufacturers are finally cranking out longer zooms like this on digital cameras, but it will cost you. An added caution, too: At these long zoom ranges, "camera shake" (see above) can blur your photos, so unless the camera has an "image stabilization" feature, plan on using these long zooms only if you have a steady hand, or have a tripod.Not many cameras currently offer image stabilization so far, but keep looking as this is a feature slowly starting to pop up on some models.
Lens The lens too, plays a very important roll in the quality of photos you take with any digital camera. You can buy a 6 megapixel camera, but if it has a cheaply made lens on it, the images may not even contain as much detail as a high quality 3 megapixel camera from a major brand. Some cheaper models of cameras have plastic or poor grades of glass for a lens, so when you're browsing Ebay and see these no-name cameras, beware - you're not getting a top quality lens on them. Other more expensive models have coated, multi-level glass lenses. While pixels and the quality of the image sensor play roles in how well your photos will turn out, neither does the job on it's own. The lens must be a high quality lens in order for you to take good photos.
If you are concerned about quality, you may want to invest in an additional lens for your camera. Most digital cameras have threading around the lens, which allows you to add additional lenses and filters.
Memory Cards Pretty much most all decent cameras today come with what are called "removable memory cards". A memory card is the "film" of a digital camera. They come in various shapes and sizes depending on the camera maker. Cards come in different memory capacities. The larger the capacity is in "megabytes" (megs for short), the more photos it will be able to store. Once you fill the card up, you simply empty it by downloading the photos into your computer, and you can then erase the card and start over. No more film and the cards can be used and reused hundreds of times before they wear out.
Memory Cards Keep your memory cards away from high heat (such as leaving them in a hot car), direct sunlight, or water.How much memory do you need? It depends on how much the camera "compresses" the image (see "compression" below), but in general, for 1.3 to 3 megapixel cameras, you really want a MINIMUM of 64 megs of memory. If the camera has a movie mode you'll be using a lot, you'll want to double that to 128 megs or even higher.
Memory Cards For 4 to 6 megapixel cameras and higher, then you really should budget for the highest amount of memory you can afford... at least a 256 meg card. Most cameras today come with what they call "starter cards" which are usually very low capacity (16 or 32 megs), and they'll only allow you to store a few photos at the camera's top quality settings. Some cameras don't even come with a card at all, but instead include a small amount of internal memory and a card slot you can put your own card in once you buy one.
The table above gives the approximate number of shots you can expect to get using low JPEG compression using various pixel count cameras in conjunction with various sized memory cards at the lowest ISO speed settings of a typical camera. The exact numbers depend on how much compression the camera applies and the ISO speed used. Higher ISO settings result in more noise and noise is hard to compress and so leads to larger files and less images per card. If you're shooting in a RAW or NEF format you can divide these numbers by 3. If you're shooting TIFF files you'd have to divide these numbers by 8.
Pixels Digital images are composed of pixels (short for picture elements). Each pixel represents the color (or gray level for black and white photos) at a single point in the image, so a pixel is like a tiny dot of a particular color. By measuring the color of an image at a large number of points, we can create a digital approximation of the image from which a copy of the original can be reconstructed. Pixels are a little like grain particles in a conventional photographic image, but arranged in a regular pattern of rows and columns and store information somewhat differently.
Bitmaps A digital image is a rectangular array of pixels sometimes called a bitmap. For photographic purposes, there are two important types of digital images—color and black and white. Color images are made up of colored pixels while black and white images are made of pixels in different shades of gray.
Black and White Images A black and white image is made up of pixels each of which holds a single number corresponding to the gray level of the image at a particular location. These gray levels span the full range from black to white in a series of very fine steps, normally 256 different grays. Since the eye can barely distinguish about 200 different gray levels, this is enough to give the illusion of a stepless tonal scale. Assuming 256 gray levels, each black and white pixel can be stored in a single byte (8 bits) of memory.
Color Images A color image is made up of pixels each of which holds three numbers corresponding to the red, green, and blue levels of the image at a particular location. Red, green, and blue (sometimes referred to as RGB) are the primary colors for mixing light —these so-called additive primary colors are different from the subtractive primary colors used for mixing paints (cyan, magenta, and yellow). Any color can be created by mixing the correct amounts of red, green, and blue light. Assuming 256 levels for each primary, each color pixel can be stored in three bytes (24 bits) of memory. This corresponds to roughly 16.7 million different possible colors. Note that for images of the same size, a black and white version will use three times less memory than a color version.
Indexed Color Images Some color images are created using a limited palette of colors, typically 256 different colors. These images are referred to as indexed color images because the data for each pixel consists of a palette index indicating which of the colors in the palette applies to that pixel. There are several problems with using indexed color to represent photographic images. First, if the image contains more different colors than are in the palette, techniques such as dithering must be applied to represent the missing colors and this degrades the image. Second, combining two indexed color images that use different palettes or even retouching part of a single indexed color image creates problems because of the limited number of available colors.
Resolution The more points at which we sample the image by measuring its color, the more detail we can capture. The density of pixels in an image is referred to as its resolution. The higher the resolution, the more information the image contains. If we keep the image size the same and increase the resolution, the image gets sharper and more detailed. Alternatively, with a higher resolution image, we can produce a larger image with the same amount of detail.
Color Terminology While pixels are normally stored within the computer according to their red, green, and blue levels, this method of specifying colors (sometimes called the RGB color space) does not correspond to the way we normally perceive and categorize colors. There are many different ways to specify colors, but the most useful ones work by separating out the hue, saturation, and brightness components of a color. In the additive color system, the primary colors are: Red Green Blue and the secondary colors are: Cyan Magenta Yellow In the subtractive color system, the roles of the primaries and secondaries are reversed.
Here is one example of using spatial relationships to illustrate how colors may be made by mixing varying intensities of red, green, and blue light. This representation is called a "color space." The percent intensity is based on a linear scale with 0% representing no light of that color to 100% representing the maximum intensity of color that may be measured with a camera or displayed on a computer screen.
Megapixels Megapixels refers to the maximum number of pixels that will make up the largest photo size for that camera. An example is that a 3 megapixel image is around 2048 by 1536 pixels in size, a 4 megapixel is around 2240 by 1680 pixels - well, you get the idea. The more megapixels you have, the larger the physical and file size of the photo will be, and the better that printed photos should look when printing them out at larger sizes.
Most monitor resolutions are in the 72 to 100 dots-per- inch range, even a small megapixel image should look good on your monitor. Today's printers can print at resolutions of up to 2880 dots-per-inch, so low megapixel camera images may not look so hot when printing them at larger sizes. What follows is a concise summary to let you know pretty much what the maximum size photo would be that you can print based on a camera's megapixel rating (keeping in mind you're using a decent printer, and good photo quality print paper, and also keeping in mind that the camera you're using is a good quality one with a good lens, etc.)
Sub-Megapixel (VGA) This would be a camera that usually has a maximum image pixel resolution of 640 by 480 or 1024 x 768 pixels, which is not large enough to classify it as a "megapixel" camera. You may see it described in some sites as a "VGA resolution camera". Images would look ok on a monitor, or for use in emails and web pages, but prints larger than 2.5 x 3.5 inches are most likely going to disappoint you. This class of camera is good for kids, and beginners who don't need A+ quality photos or do not need to print many photos.
1 Megapixel In the 1280 by 960 pixel range. Good images on screen and decent prints up to 4 x 6 inches. If the camera has a good quality glass lens, you can perhaps crank out a pretty good 5 x 7 too, but this usually comes from older models that were made better. Today's 1 megapixel cameras are usually third-party or off-brand models that aren't as well made as "cutting edge" models were 4-6 years ago. There are tons of cheaper made cameras coming out in this pixel range, and many companies are cranking out cheap "duds", too. Stick with the name brands in this category or look on Ebay for the older models from them.
2 Megapixel In the 1600 by 1200 pixel range. More detailed images on screen. Usually good 4 x 6 and decent 5 x 7 prints, provided the camera has a good lens, plus some pretty good 8 x 10 prints from cameras with an extra good lens and name brand on them. ("Good" not meaning "35mm film quality", however). You could compare larger prints from these cameras as being about the same quality as a cheaper 35mm film camera, but again, the on-screen photos will look very nice at least.
3 - 4 Megapixel In the 2048 by 1536 pixel range and higher. Great screen images. Better 8 x 10 prints. This class of camera is pushed heavily in stores to first time buyers as a "starter size". If you like to do a lot of 8 x 10 prints and want them to look good, 3 megapixels is usually the happy spot between good prices and good features. For many of today's everyday users, I personally think a good quality 3 to 4 megapixel camera is sufficient for most casual everyday uses.
5 - 8 Megapixel and higher In the 2592 x 1944 and higher pixel range. Near 35mm photo quality 8 x 10 prints in the 5 megapixel range, and 11 x 14 prints and higher from 6-7 megapixels onward. Big time overkill for those just wanting to view photos on their computers or want to stick them on their web pages or just print small snapshots. If you're super nutty about your 8 x 10 prints looking "perfect", or need to make super large prints (larger than 11 x 14), then you may wish to look at the 8 megapixel models, or even the more professional digital SLR models (have your American Express ready!).
Aspect Ratio The aspect ratio of a camera is the ratio of the length of the sides of the images. For example, a traditional 35mm film frame is approximately 36mm wide and 24mm HIGH. This has an aspect ratio of 36:24, which can equally well be expressed as 3:2. Some digicams use the same aspect ratio for their digital images. For example most digital SLR (single lens reflex) cameras have a 3:2 aspect ratio. However, video monitors typically use a 4:3 aspect ratio. For example a monitor with a 800x600 display has a 4:3 aspect ratio. With this in mind, most consumer level digicams use a 4:3 aspect ratio for their images.
Image Types: JPEG, TIFF and RAW The size of the digital file corresponding to the image which the camera produces depends on the pixel count. In most consumer digicams each pixel generates 3 bytes of data (so called "8-bit data"). One for red, one for green and one for blue. This means that a 3MP camera, which has 3 million pixels, generates 9 million bytes of data, or 9MB (megabytes). A few cameras can generate extra data for extra quality, and some of these cameras generate files which correspond to 2 bytes of data for each color ("16-bit"), so a 3MP camera which is capable of generating 16-bit data will produce an 18MB image file.
These files are pretty big and they can be compressed quite a lot without a significant drop in quality. This is where JPEG (Joint Photo Experts Group) comes in. JPEG is an algorithm designed to work with continuous tone photographic images) which takes image data and compresses it in a lossy manner (this means you do lose some information). The more you compress, the smaller the file but the more information you lose. However, you can reduce file size by a factor of 10 or so and still get a very high quality image, just about as good as the uncompressed image for most purposes. You can reduce the file size by a factor of 40 - or even more - but the image starts to look really bad!
With 10:1 compression the 8-bit files generated by a 3MP camera would be 900Kbytes in size rather than 9Mbytes, which is a big saving with little quality loss. The smaller files take up much less storage space and are much faster to send between computers or from the digital camera or memory card to a computer. There are also lossless ways of saving files using TIFF (Tagged Image File Format). These keep all the original information, but at the cost of much bigger files. TIFF files can be compressed in a non-lossy way, but they don't get very much smaller. TIFF files can also be used to save 16-bit data (those these files are twice the size of 8-bit data files), JPEG files can only save 8-bit data.