ISO Settings

ISO in digital camera is a numeric representation of a camera's sensor relative sensitivity to lights. The ISO could range from 100, 200, 400, 800, some latest model could boost up to 12800 and 25600.

Lower ISO will produce better overall image quality, but it will require a longer shutter speed or larger lens apertures, which themselves reduce the image sharpness. Higher ISO will allow more lights in, resulted in brighter photo, which increased the amount of noise on the photo. Selecting the right ISO sensitivity is a matter of deciding on the sensitivity that provides the right combination of image noise, shutter speed and aperture.

I took some photo with Nikon D40X with different ISO so you could see the clear different.

ISO 100
Image is sharp and pretty dark.

 ISO 200
Image still look sharp, slightly brighter than ISO 100.

 ISO 400

Still looks good.

ISO 800 

Image is bright, but notice that there are extra white dots, which is the noise.

ISO 1600

Image are much brighter with more noise. 

ISO 3200

At 3200, it is very much exposed, but with the high noise level.

Understanding Metering modes

What is metering modes? How do we use them? In shorts, metering modes refers to the way that the camera determines its exposure. The most common modes found on DSLR are Center-Weighted, Spot and Matrix.

Center-Weighted
In this mode, the center circle carries more "weight" when the light meter averages out the brightness across the scene. The meter will cover around 75 percent through the view finder, at which the center are is well exposed. This mode is best to use when you shoot portraits and close-up.


Spot
In Spot metering, the camera will measures the small circle in the center of the view finder, between 1 to 5 percent. It is commonly used to produced high contrast photos. As the camera focus on this small area, it tends to ignores the exposure outside this spot. It is best to use if there is dramatic in illumination between the subject and the surroundings,particularly if the subject is not fast moving. One good example is use to shoot the moon.

Matrix

This is the standard metering mode. This is an all-around metering where the camera system will decide the exposure for the situation. When the camera decide the level of exposure, it will take into account the autofocus, distance to subject. Best to use for daily photography.