ISO is the camera sensor's sensitivity to light. The lower the ISO number, the less sensitive the sensor is to light. The higher the ISO is, the more sensitive the sensor is to light. A high ISO is helpful in low light situations because it allows the camera sensor to become more sensitive to light. A downside to using a high ISO is digital noise. Digital noise is distortion in your image that makes it look grainy. Digital noise happens when the sensor cannot pick up all the information needed for the image. ISO is yet another component of the camera that reinforces how important light is to photography.

Understanding ISO 

The ISO is the next step in understanding how light works in photography. Using the ISO along with aperture and shutter speed, a photographer can make images that bring wonder into photography! The ISO is software that controls the level of sensitivity of the digital sensor to available light. This level of sensitivity allows the camera to take images in low light as well as bright light.

Many photographers know how to control light, and by doing so, they can keep taking photographs well after the sun goes down. The lower the ISO number, the less sensitive the digital sensor is to the light. The higher the ISO number is, the more sensitive the camera's digital sensor will be to light. The below diagram shows the direction and sensitivity of the camera to light as it corresponds to the numbers.

In many cases, when the photographer decides to take the camera out of automatic ISO, he/she has already had a good understanding of how the shutter speed and aperture work together to control light. The manual ISO is the only setting on the camera that will work together with other camera modes without being in full manual mode. By placing the ISO on manual ISO, the photographer can choose two out of the three settings to control the exposure while still being in one of the automatic modes.


Low Light

When you are in a low light scenario, you will need to use a higher ISO to make your camera more sensitive to light; thus, allowing it to make the correct exposure. When your subject is well lit and you have a lot of light, such as outside in direct sunlight, you will want to use a lower ISO to make your camera less sensitive to light; thus, allowing your camera to make the correct exposure.

Changing the sensitivity to light is useful when you're shooting in different lighting situations – particularly when there's low light and you may not be able to use a flash. In this case, you can bump up your ISO setting in your camera to make its digital sensor more light-sensitive

Yet, there are many reasons to use a higher ISO when there is a lot of light. For instance, if the photographer is taking photos outside in direct sunlight at a sporting event where the players are moving fast. The photographer will want to use a faster shutter speed, meaning that the shutter will be open for less time, making the image darker. Having the digital sensor more sensitive to light will allow the sensor to wright the images faster, meaning that the shutter does not need to be open as long.

Digital Noise

A unique attribute of a high ISO number is, the more sensitive you make your digital sensor, the more digital noise your image will have. In digital photographs, "noise" is the commonly used term to describe visual distortion. It looks similar to grain found in film photographs. It can also look like splotches of discoloration when it is spotty and can ruin a picture. Noise tends to get worse when you are shooting in low light.

You probably won't notice the graininess in your images when looking at them on the screen on your camera; however, when you upload your images to your computer, they'll become noticeable in images that use higher ISO settings. The above diagram shows the direction and the sensitivity of the camera to light as it corresponds to the numbers and the digital noise.

Digital noise comes from the digital sensor's inability to capture all the information that it is receiving during an exposure. This is because the sensor is made from Digital data called pixels or also known as Bit Maps. The word pixel means a picture element. Every photograph, in digital form, is made up of pixels. Pixels are the smallest unit of information that makes up a picture. Usually square, they are typically arranged in a 2-dimensional grid or better known as bit maps. Each bitmap holds information on the image like hue, saturation, and brightness; this information can be found in each pixel. This information is stored in either three components, known as RGB (red, green, blue), or four elements, known as CMYK (cyan, magenta, yellow, black).

These components RGB and CMYK are critical to the end image. Each format has a specific use RGB refers to a system for representing the colors to be used on a computer display. Red, green, and blue can be combined in various proportions to obtain any color in the visible spectrum. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and black. The use of K for black is not accidental. The 'K' is used because in printing, all colors are aligned with the Black plate; it is also the last letter of the word "Black" and is not occupied by any other color.

The number of pixels in an image is sometimes called the resolution. Resolution is the detail in an image. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail. Image resolution can be measured in various ways.

The measure of how closely lines can be resolved in an image is called the spatial resolution. It depends on the system's properties, creating the image, not just the pixel resolution in pixels per inch (PPI). ... In effect, spatial resolution refers to the number of independent pixel values per unit length.

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