Metering Mode

Lightmeters in digital cameras are intelligent enough to automatically determine the correct exposure for most shots so the photographer can concentrate on composing the image. They all work on the principle of measuring reflected light from the subject.

The three most common types are:

Matrix or Evaluative metering divides the image area into many small segments and analyses the readings for the best possible exposure. It is remarkably accurate in most situations.

Center-weighted metering asesses the whole image area but assigns the most importance to the central 40 to 60%. This system is accurate in average lighting conditions, but can be fooled by excessively dark or light areas. Used for general and portrait photography.

Spot metering only evaluates a small area in the center of the viewfinder so you can meter for a specific detail of the scene. Use when photographing a subject against a bright or dark background, also useful for macro photography.

Automatic exposure modes work fine for most scenes, but the meter can only see scenes as neutral gray and compensates for any deviations accordingly. So you should know when to override the meter's results. If the subject contains more than average dark or light tones you should take a substitute reading of an average gray area, lock that exposure and then recompose the image and release the shutter. Green grass or medium blue sky are good examples of average gray.

Focal Length

Focal lenth is the distance from the lens to the image sensor (or film), when focused on something closer than infinity, the lens is moved farther away from the image sensor. This is why most lenses get longer when you zoom In.

In 35mm photography, lenses with a focal length of 50mm are called "normal" because they work without reduction or magnification and create images the way we see the scene with our naked eyes. Focal length less than 20mm are called "Super Wide Angle", 24mm - 35m are called "Wide Angle", 80mm - 300mm are called "Tele" and beyond 300mm are called "Super Tele".

Attached eight photos were taken from the same place with Panasonic DMC-FZ8 digital camera by using different focal length from 36mm to 648mm, the 8th photo is taken with 4x digital zoom. (Digital zoom is not really zoom in the strictest definition of the term. What digital zoom does is enlarge a portion of the image, thus 'simulating' optical zoom. In other words, the camera crops a portion of the image and then enlarges it back to size. In so doing, you lose image quality.)

What is ISO in digital camera?

(Shot with Panasonic DMC-FZ8 - ISO 400 | F2.8 | 1/8 s)

What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.

ISO Speed & Exposure

ISO speed affects the shutter speed / aperture combinations you can use to obtain correct exposure.

Suppose your digital camera's light meter warns you there is not enough light to correctly expose a scene. You could use the on-board flash, but let's suppose again it's not allowed (like in a concert or indoors recital). You would then need to use a higher ISO. Set on "ISO Auto" mode, your digital camera will automatically select a higher ISO. Otherwise, you can manually select the next higher ISO and see if the increased sensitivity allows you to obtain a correctly exposed picture.

Similarly, if you find the camera is using a shutter speed that is too slow (1/60 sec. and slower) to handhold the camera steady and shake-free (thus resulting in blurred pictures), and you cannot open up the aperture anymore, and you do not have a tripod or other means to hold the camera steady, and you want to capture the action, etc. -- then you might select the next higher ISO which will then allow you to select a faster shutter speed.

ISO Speed & Noise

when you boost the sensitivity of your image sensor by selecting a higher ISO, the image sensor is now able to record a fainter light signal. However, it is also true now that it will record fainter noise, where noise is any signal that is not attributed to the light from your subject.

ISO Speed & Image Sensor Size

The size of the image sensor determines the ISO speed range that a digital camera can use without suffering from undue noise. One reason for this is because the pixels on the larger image sensor can be larger and therefore receive more light, and thus have a greater signal-to-noise (S/N) ratio.

Tips:

* Using the lowest ISO possible on your digital camera will give you the best image quality your digital camera is capable of.
* If you want to take pictures indoors where light may not be sufficient and in other low-light situations, then you would need to supplement existing light with flash or studio lights. Either that, or select a higher ISO. Bear in mind, a higher ISO may mean a noisy image.
* If you are printing mostly 4x6 in., you may find the noise is not evident in the prints (and so you don't need to worry about noise at high ISO) though they may be visible at original sizes on screen.

Meadow Stadium Bonfire Night Fireworks Show

The biggest fireworks show in Edinburgh on Bonfire Night held in Meadowbank Stadium. This video is captured by Panasonic DMC-FZ8 on Carlton Hill (It was windy and freezing on the carlton hill). After converted the original MOV format of video to AVI format, the quality drop quite a lot, so did the file size.