Monday, December 3, 2007

Photographic filters

Photographic filters have been in use for a long time. They were required for special effects or to enhance the contrast of some colors. They were also used for white balance.
For example, a film set for daylight color temperature, would have produced yellowish photos when taken inside, with incandescent light bulbs lighting the scene. To compensate, a blue filter had to be used, to get the right colors.
The major advantage of digital cameras is the fact that you can adjust the white balance of a scene electronically, without the use of a color filter. As far as the image effects that could be obtained with some filters (like blurring the image, changing color hue for specific areas of a photograph, etc.) there are better ways of getting them onto a photo.
Very cheap image software can produce more effects on a photograph than all the filters in the world combined. With a little bit of imagination, using software to get the effects you want is the best way to go.
The only filter a digital camera actually needs is a polarizer.
Polarizers come in two varieties:Linear polarizers Circular polarizers
Each has the same effect but circular polarizers are more expensive. Digital cameras can use both (linear and circular) polarizers.
Polarizers produce deeper colored blue skies, minimize light reflections from glass and water and reduces glare from non-metallic surfaces. They also provide good color saturation. Can be used in extremely bright light situations to reduce the amount of light entering the camera; this enables more selective depth of field control.

Exposure Compensation

Exposure Compensation is a feature on a digital camera that allows you to adjust the shutter speed measured by its light meter. Usually, the range of adjustment goes from +2 to -2 EV in 1/3 steps.
Lets say that you point the camera at you subject and the meter says you need 1/250 sec. shutter speed at aperture 5.
If for whatever reason you select +1 exposure compensation, the shutter speed used by the camera will be 1/125 sec.
If you use -1 exposure compensation, the shutter speed will be 1/500 sec.
Every increment in exposure compensation (+2 +1 -1 -2) increases or decreases the amount of light going through the camera by a factor of 2.

White Balance

The white balance setting for a digital camera is very useful in dealing with various light conditions. The best way to understand this setting is to place a white sheet of paper in front of your camera and take a photograph.
If the image has a white sheet of paper in it, you're ok; but if the paper has a yellowish hue, you're in trouble.
To better understand this process, take a look at your lamp. It usually uses an incandescent bulb. If you look closely, you'll notice that the color of this particular source of light has a yellow hue. The digital camera amplifies this hue and you get a yellowish photograph.
So, before taking any photo, look around at your sources of light। Even if you are outdoors, there are white balance settings that will make your photo look a lot better.

Daylight white balance
Cloudy white balance
Tungsten white balance
Fluorescent white balance
Flash white balance

Focal Length

The focal length of a digital camera lens is the distance between the center of the lens and the image sensor when an in-focus image is formed. The focal length of a digital camera lens is displayed on the barrel of the lens along with the measurement of the largest aperture and the maker.
The focal length of a lens establishes the field of view of the camera. The shorter the focal length is, the larger the field of view.
Camera lenses are categorized into normal, telephoto, and wide angle, according to focal length. Thus a 200 mm equivalent telephoto lens gives a 4 x magnification over the 50 mm equivalent lens.

Image Format

Digital cameras store the images they produce in two different formats: JPEG and RAW. JPEG is the most common used image format, while RAW is usually used by professionals.
The differences between the two go beyond the image size. A JPEG image is a compressed image, for example, an 8 MB RAW image can be compressed to a 3 MB full quality JPEG.
The RAW format produces much more that a BIG image. It also has been described as a "digital negative". Professional photographers use RAW because they can make later modification to the image that wouldn't be possible using JPEG.
The disadvantage is the fact that you need specialized expensive software to read and modify RAW format images. You also need time and patience. Let's say that you make 100 photos in RAW format and 100 photos in JPEG.
The JPEG images are ready to use, you may discard 20 of them because of bad exposure, but you have the rest of the images ready to be printed or to be published on the Internet.
With RAW images, you'll need at least 1-2 hours of opening the 100 images with photo editing software and tweak their properties to the point when you'll get the image you want.

Image Stabilization

Image Stabilization is also known as vibration reduction and anti-shake; it is a technology found on digital cameras with long telephoto zooms (10X and 12X). It helps prevent images from becoming blurred.
This technology helps people in taking photos that require slow shutter speeds. The system works in two different modes. There are systems that stabilize the shot by moving the image sensor or by moving optical elements inside the lens.
This anti-shake system can make the use of a tripod redundant, but there are situations when at very slow shutter speeds (>1 sec.) the image stabilization cannot cope with the movement of a hand held camera.

Image resolution

Is the most talked about feature of a digital camera. From 3 to 12 megapixels or more, it seems that with every generation of digital camera there is an increase in image resolution.
But what is a megapixel? Well, a megapixel is represented by 1000000 pixels.
So, if the maximum resolution of a digital camera, results in an image 3000 pixels in width and 2300 pixels in height, that camera would be a 3000 x 2300 = 6900000 / 1000000 = 6.9 MEGAPIXELS
When talking about megaspixels, there is the question: how much do you need? Especially because the more a camera is capable, the more expensive it is.
If you are going to use the images on the Internet, you may find that the maximum resolution of 1600 x 1200 might be enough. That would lead you to buy a 1.92 Mpx camera!
If you want to print an image, you need to consider the dpi requirements. 300 dots per inch is a standard in printing any image. It simply means that all you have to do to find out the maximum width of a printed image is to divide its width in pixels by 300.
3000 pixels / 300 = 10 inches maximum.
However, the more megapixels a camera has, the better the optics on that camera, and so you get far better images.

ISO Speed

ISO speed shows how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive is the image sensor.
The ISO is represented by numbers:
ISO 50 100 200 400 800 1600 3200

Each number represents two times the sensitivity than the previous one। Higher ISO settings are very useful in low light situations, but the disadvantage of noise appears. The higher the ISO, the higher the noise levels you get.

Shutter Speed

The shutter is a mechanism that controls the exposure time of an image. This time can be manually set by using the shutter priority shooting mode from your digital camera. The numbers you'll use will look probably like this: 15, 13, 10, 8, 6, 5, 4, 3.2, 2.5, 2, 1.6, 1.3, 1, 0.8, 0.6, 0.5, 0.4, 0.3, 1/4, 1/5, 1/6, 1/8, 1/10, 1/13, 1/15, 1/20, 1/25, 1/30, 1/40, 1/50, 1/60, 1/80, 1/100, 1/125, 1/160, 1/200, 1/250, 1/320, 1/400, 1/500, 1/640, 1/800, 1/1000, 1/1250, 1/1600, 1/2000 sec.
These numbers represent how long the light will be allowed to hit the digital sensor in order to capture the image


Aperture is a device that controls the quantity of light that passes through the lens। It is an iris type mechanism, which shrinks or grows in order to let in less or more light.

Each number lets in two times less light than the previous one.
Small numbers represent a large aperture, big numbers - small aperture. Most digital cameras do not have this numbers written on their lenses, but they use aperture as part of their construction. It is also the way for you to select aperture priority shooting mode from your camera to control the depth of field.