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Big 3: Sensor Size, Lens, Megapixels. What do you need? |
| As you are reading the following sections about Resolution, Lenses, and Sensors keep in mind that individually they only make up one-third of the major parts. All three are equally important in creating good quality images and share responsibility to capture good quality images. Some digital cameras have megapixels so high that the sensor size becomes the bottle neck. This means that camera may not be taking full advantage of all its megapixels. Digital SLRs, with a lower resolution and a larger sensor, will render a better quality image than a compact camera with higher megapixels. This is because the sensor itself is larger and the lens is better quality. Finally, remember to use this technical information as a guide and do not get too wrapped up in megapixels, sensors and flux capacitors. The best camera is the one you use. |
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| What is a Pixel? A pixel is the single building block of a digital image. Pixels cannot be seen in an image with the naked eye unless enlarged greatly. Pixels are also on or off. To create colors, pixels are filtered with one of the primary colors of light (red, green, blue) and are placed next to each other. When viewed, the colored pixels mix optically and become a solid color. |
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What does resolution mean? Resolution is the amount of information being captured. It is based on the sensor and the amount of pixels. 1 megapixel equals 1 million pixels. The higher the resolution, the better the picture quality. However, a very small sensor can only take advantage of so many pixels. As the pixels get smaller, they are more susceptible to noise and require software to sharpen the picture. Many compact cameras now use a heavy amount of software sharpening, to counter the effect of the extremely small pixels. This can degrade the overall quality of the picture.
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| The actual explanation of resolution is some what technical. Feel free to skip this next paragraph if you do not feel the need to get more technical. Resolution is the measure of the amount of pixels on both the horizontal and vertical axis. Sensors are horizontally oriented. 640x480 means 640 pixels on the horizontal axis and 480 pixels on the vertical. To get the megapixels from a given resolution, multiply the pixels length by the pixels width. So 640x480 in megapixels equals 307K. Not even 1 megapixel.640x480 is typically used as TV resolution on cameras. An 8 megapixel digital camera can record at 3504x2336. When multiplied together, that equals 8.18 million pixels. The next measure to look at is Pixels Per Inch (PPI) which measures how large a print can be made from a file. On average, to get a high quality print, you need at least 300ppi.Which means, for every inch or print per axis you need 300 pixels. Here is an example, with a resolution of 3072x2304, a good quality 8x10 print could be made. With 3072 pixels, that equals 10.24 inchs at 300ppi. 2304 pixels equals 7.68 inches at 300ppi Keep in mind that other variables such as image compression and computer processing also make a difference in the size of print that can be made. |
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Compression and File Type: Most files coming from a digital camera have some sort of image compression. Compression leaves out unused data from the picture. This organizes the file data and decreases the file size. Files with higher compression loose more data. This can cause problems down the road when trying to edit pictures on the computer. The data lost during compression can possibly be needed to correct for brightness and color. If the data is not there, the image pixalizes and "falls apart." The data loss will be noticed in curves, high contrast areas and darker but not black areas of the picture first. You may also notice what is called artifacts. These look like pixelized halos around edges of objects in the prints.
On many cameras, there are Small, Medium, and Large settings in addition to the resolution setting. These settings affect the amount of compression. The largest factor in determining the overall quality of the picture, is how discrimintating the eye of the viewer is. JPEG is the most common file type for digital cameras. Typically, the bigger the file size, the better the file quality. Most high res JPEG images should be at least 4 MB. Files smaller in size but above 2 MB will make smaller prints around 4x6. On the extreme low end, files smaller than 1 MB will only be viewable on a monitor with good quality. Most digital cameras 4 or 5 megapixels or more will make nice quality 4x6 to 8x10 prints. RAW is a file type which has the ability to capture data directly from the sensor without any compression. These files are usually the largest in size and have the best quality. They will also provide the most information when editing them on the computer. So does this mean you must go out and buy a camera with RAW files and the largest file size? Not really. JPEG files can render pictures up to 16x20 and unless you are interested in creating large prints or working heavily on the computer, you do not need that capability. For most people, JPEG files will work idealy to capture those moments. |
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Sensors: The sensor is the device which records light. Sensors are comprised of light sensitive pixels, which convert light into an electrical signal. There are 2 main categories of sensors. The first is CCD. These are used on most compact digital cameras and some digital SLRs. CCD technology has been around for over a decade and has been used in numerous types of devices. CCDs are also able to devote the entire pixel surface to light gathering. The other catagory is a CMOS sensor. CMOS sensors have the image processing built into the sensor. CMOS sensors also use a great deal less battery power than CCDs and are more easily produced in larger sizes.
The size of the sensor absolutely does matter. There is a point where only so many pixels can be crammed onto an ultra small sensor. Then the size of the sensor becomes the limiting factor versus the resolution available. Extremely small pixels tend to have more noise. Currently, most of the digital SLRs cameras have an APS sized sensor. APS is about half the size of a 35mm negative. Some of the higher end SLRs have full frame, 35mm sized sensors. Compact digital camera sensors range in size from very tiny, to APS size. |
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Memory Cards: Memory cards are the digital media which stores your pictures. There are a few different types of cards being used. Currently the 2 most widely used card types are Compact Flash (CF) and Secure Digital (SD). These two types of cards are being used by the widest variety of cameras and other electronic devices. Memory Stick and Memory Stick DUO is used by Sony exclusively. xD cards are being used by Fuji and Olympus cameras. Most compact digital cameras from brands other than Sony, Fuji and Olympus are using secure digital. Many of the digital SLR cameras are using compact flash. However, the less expensive digital SLRs have switched to SD. Microdrives are the only type of card with moving parts. They are similar to minature harddrives and have very small spinning disks. Microdrives are similiar in size to compact flash and are slightly more fragile. They do not take drops or jolts well. However, microdrives are good for large amounts of storage for less money than compact flash. Keep in mind, not all cameras which use compact flash will use microdrives.
Dos and Don'ts: Microdrives are somewhat fragile since they have moving parts. Do not drop them. The other types of cards are quite durable. Cards are resistant to airport x-rays, are not light sensisitive, and a sealed well enough that a little dust or moisture will not hurt them. However, very strong electromagnetic fields can damage them. Keep your cards either in the camera or in a case. Cards can get damaged, so take care of your memory cards. They may contain images that you do not want lost.
Do not under any circumstances, take out the card while the camera is on. You can corrupt all your images.
Many cards now come in high speeds. High speed cards are recomended for digital SLRs to help deal with the larger file sizes. Some compact cameras support high speed cards and if you plan on taking video with your camera, a high speed card will help.
If you accidentally erase all of your pictures, don't panic. There is a good chance, not a guarantee, that your pictures can be recovered. Many photolabs, including Tall's Camera, have the ability to recover images from memory cards. Most importantly, if this happens, do not use that card until you take it in for recovery. The only chance you have, is if the pictures have not been written over by a new picture. |
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White Balance: White balance is what the camera defines as white. This sets the stage for all other colors captured. Light has different colors depending on the source. Examples: Daylight is blue, tungsten is yellow, and florescent is green. When you change the white balance on your camera, you are telling it that the available light is that color. You can also use white balance to give your pictures an overall tone. This can also be done afterward on the computer. If toning the picture, you will get better overall results in the camera. However, once you take a picture in one white balance mode, you cannot change it back. The exception to this is the RAW file type. Since RAW files are unprocessed data from the sensor, you can change the white balance during the image conversion to the computer.
The more technical explanation. Skip this if you so desire. White balance is based on color temperature. Measured in degrees Kelvin (K), the color of light can be measured and charted. Candle light is the lowest measured at 1850-1930K. Bright daylight is the highest measuring at about 10,000K. As the temperature goes up the color gets cooler. Reds and yellows are considered to be very warm in color and have the lowest color temperture. Blues and whites are considered to be very cold and have the highest color temperature. The intensity of the light has no effect on color temperature. Photographic color of light only refers to the relative intensity of blue to red. Tricky situations will occur when trying to photograph under mixed types of light. For example, using a tungsten light on a subject with daylight coming in through a window. |
Top: Color Temperature of 6500K
Above: Color Temperture of 4100K
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Batteries Gone are the days of having the same camera battery for a year or more. Digital cameras are electronic devices and drain batteries much quicker than film cameras. With any type of battery for a digital camera, don't be left in the dark, be ready with extras and/or a charger. Digital camera batteries can be broken down into two basic categories: AA type and Lithium Ion rechargable. |
| AAs are available at most stores and are used in what seems just about everything. However, regular Alkaline batteries do not have good life in digital cameras. It will seem that every time you go to take a picture, your batteries are dead. This does not mean that the cameras which use AAs are bad cameras. A recommended substitute would be rechargable AAs. The magic number for rechargable AAs is the millaAmp (mAh). The higher the number, the longer the life. 2300mAh is a good starting point. A disposible option is Lithium or Oxy-Nickel AAs. These are more expensive than alkalines, but the lifetime of the batteries will make up the difference. Some, not all, cameras will take a CR-V3, which is another substitute for AAs. These will give you the best life for this form factor. |
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| Lithium Ion (Li-ion) batteries are becoming more popular as digital cameras use more power. These are unique to the model of the camera and are rechargable. The cameras that use these batteries will also come with a charger. Lithium-ion batteries will perform better and last longer than any type of AA size battery. These batteries are also more expensive to replace than a set of AAs even with a charger. You also most likely have to go to a camera retailer which carries the model of camera to find the battery. Cold weather saps the life of all batteries, but lithium-ions will hold their charge the best. They have no memory as far a recharging and typically have a charge time of about 4 hours. However, whatever time you can give them, they will take and be usable accordingly. Lithium-ion batteries are being used not only in digital cameras, but cell phones, PDAs, laptops and many other electronic devices. |
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