ISO and its Effect on Image Quality

 

ISO (International Organization for Standardization) is one of the three elements that make up the exposure triangle.  The other two are shutter speed and aperture. In film photography, it measures how sensitive the film is to light and in digital photography, ISO measures the sensitivity of the camera sensor to the light.  Adjusting the ISO greatly affects the fineness of the image since it direct impacts how much film grain or image noise will be visible.

prawns ISO and its Effect on Image Quality

The principles of ISO are the same for both film and digital photography. ISO is measured with the numbers 80, 100, 200, 400 and so on. Some high-end cameras feature numbers as high as ISO 3200. When you lessen the ISO number, the grain or noise becomes less visible. This makes the image look finer and have a better image quality. The higher the ISO number, the more sensitive the camera is to the light and the more obvious the image noise. This makes the image appear grainy and it loses some of its quality. Graininess is not necessarily a bad thing especially if you're using it deliberately to create a mood. In this case, a very high ISO would be ideal.

Just like shutter speed and aperture, ISO is adjusted depending on the available light. ISO 100 is an ideal setting because your images retain their fineness and crispness. However, in low light conditions, you might need to maintain a fast shutter speed or a small aperture in which case you might be forced to increase the ISO settings in order to capture more light. The result is a better lighted image but the repercussion is a more grainy effect.

The common low light situations are indoor birthday parties, indoor sporting events or games, and night scenes. There are places which do not allow you to use flash such as galleries or theatres so to compensate for inadequate lighting, a higher ISO might be used.

A lot of beginner photographers use Auto mode, which does the job of automatically selecting the ISO settings based on the scene. It is advisable that you use Manual mode whenever possible so you can practice adjusting the exposure settings. You will then have more control over the outcome of the image. 


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Understanding the Histogram

One of the most useful yet most ignored camera features is the histogram. The histogram is available in most, if not all, digital cameras. It can be viewed in the LCD while you are also composing your shot, or separately after the image is taken.

histogram Understanding the Histogram

What does a histogram do, exactly? Simply put, it measures the brightness of a scene.  You will see a graph with a strip below it showing black at the left and white at the right, with all the gradients of gray in between. This includes all the pixels in your image.  Now the graph counts the number or pixels at each level between the black and white areas in an image. The deepest darkest shadows are to the left of the graph and the bright highlights are found at the right. The heights of points in the graph shows how many pixels are found at a certain brightness level.

If your image is underexposed and is very dark, most of the pixels will be situated at the left side of the histogram, probably even hitting the left edge. If the scene is too bright, majority of the pixels will be at the right side. This histogram shows most of the pixels in the middle area, which means the scene or image is more or less evenly exposed. An evenly spread pixel area doesn’t mean your image is now perfect, just that the exposure is balanced. The histogram of a dark key image might show most of the pixels at the left of the graph but that’s okay because you intentionally are making the image dark.

Although the best judge of the exposure of a scene is still our eyes, the histogram can greatly aid us when it is hard to see the image in the LCD such as when we are out in the sunlight. With this graph, we can also foresee whether the scene will come out too dark or too bright and we can adjust our camera settings accordingly. 


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Understanding Exposure – Part 2: Auto/Manual Exposure, Reciprocity, and Light Meters

The subject of exposure is very broad since it is the foundation of the medium of photography. To have more control over your camera’s output, it is best to understand the various concepts of exposure. Here are more information regarding exposure, from how its elements interact, to the various ways it is measured.

Cameras have automatic and/or manual exposures. By using the auto mode, the camera decides the best exposure settings based on the subject’s mid-tone.

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Understanding Exposure – Part 1: Exposure Triangle

Photography has so many technical terms and jargon that it can all get so confusing at times. One thing that any photographer should fully understand, though, is exposure. Photography means ‘capturing the light’ and exposure is the total amount of light that reaches the film (traditional photography) or sensor (digital photography).

Exposure is defined by three elements which make up the ‘exposure triangle’. These would be ISO, aperture and shutter speed. These are all connected to each other and by adjusting any of these settings, you must keep the other two in mind.

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