For beginners: Understanding exposure in 3 steps. Step 3: understanding ISO.

There are 3 factors which determine the exposure of a photo: ISO (International Standards Organization), aperture and shutter speed.

ISO is the level of sensitivity of your camera to available light. The lower the ISO number, the less sensitive it is to the light, while a higher ISO number increases the sensitivity of your camera.

The ISO scale typically starts at 100, and continues to double: 100, 200, 400, 800, 1600, 3200, 6400. Each step between the numbers doubles the sensitivity of the camera. For example, ISO 200 is twice more sensitive than ISO 100. It means that it needs two times less time to capture an image.

At lower ISO numbers photographs will be clean and crisp.

With increased sensitivity, your camera can capture images in low-light conditions without using a flash. But higher sensitivity adds grain or “noise” to the pictures. Digital photography is composed of lots of little squares (the grain) which come together to create an image. Sometimes (at higher ISO numbers) those little squares in the image become slightly visible and this is referred to as “noise”.

Every camera has so called “base ISO”, which is the lowest ISO number that can produce the highest image quality, without adding noise to the picture. On most of the cameras the base ISO is typically 100 – 200. As a general rule, the lower the number, the better the quality of the photo.

How to determine what ISO number to use?

ISO 100-200: great for shooting outdoors in daylight. Your photos will have the most clear details and the best quality.

ISO 200-400: good for slightly darker conditions (in the shade, at the cloudy day or indoors with bright light).

ISO 400-800: good for shooting with a flash indoors.

ISO 800-1600: good in low light conditions where flash is prohibited.

ISO 1600-3200: it’s used in extremely low light conditions, it’s impossible to avoid “noise”.

A low ISO number would give a low exposure and a high ISO would give a high exposure. This is much easier to demonstrate using photos. The photos are displayed in the following order: auto mode, 100, 200, 400, 800, 1600, 3200, 6400. The aperture (f/4.5) and shutter speed (1/320) remain constant, only the ISO is changing, so you can clearly see its effect on a photo.

The ideal exposure is shown in the fifth photo, which was taken at ISO 800.

ISO (auto).

 ISO 100.

 ISO 200.

ISO 400.

 ISO 800.

 ISO 1600.

 ISO 3200.

 ISO 6400.

Thank you for reading.

If you have any questions or comments, please post them.

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For beginners: Understanding exposure in 3 steps. Step 2: understanding Shutter Speed.

I hope that you feel confident in understanding aperture.

The shutter is closed all of the time, except from when a photograph is being taken.  To create an image we need light to get through to the camera sensor. Shutter is a device that controls the moment when light gets to the camera and the length of time for which the light passes into the camera – the exposure time. The longer the exposure time, the brighter an image. First you press the shutter release button.

 The shutter speed is the amount of time your shutter stays open when you click the button. If the shutter is opened for too long, the photo will be overexposed (too bright), if it’s not open for long enough time the photo will be underexposed (too dark).

Shutter speed is measured in seconds or more often in fractions of a second:

1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1.

The larger the number of the denominator the faster the speed, for example, 1/500 is faster than 1/60 and your shutter will be opened for less time if you set it at 1/500 than at 1/60.

If you look through the viewfinder (which is a name for the little window in the camera body), it should also be the number on the bottom left side of the electronic screen. On most digital cameras you will not see the shutter speed as a fraction of a second but it will be a regular number. For example, when the shutter speed is slower than or equals to one second, it will be looking as 1″ or 5″ (the ″ sign indicates a full second).

You’ll be using shutter speeds of 1/60 of a second or faster in most cases because when you are using a slow shutter speed (slower than 1/60) you will need a tripod. Otherwise your camera will be moving when the shutter is opened (it’s called “camera shake”) and it is blur in photos.

When something/someone in your scene is moving, you have a choice how to capture the moment. You can freeze the movement (so it looks still) by selecting faster shutter speed in the settings on your camera. You can let the moving object intentionally to be blur by selecting a slower shutter speed.

 

 

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For beginners: Understanding exposure in 3 steps. Step 1: understanding aperture.

The word photography etymologically means “drawing with light”. So exposure is all about how much light you let into your camera: if there is too much of it, your photo will be too bright (overexposed), and if too little, your photo will be too dark (underexposed).

Here you can see 3 photos: 1) good exposure, 2) underexposed, 3) overexposed.

   

The photo with good exposure.

This photo is too dark - underexposed.

 This photo is too bright - overexposed.

How light or how dark your photograph depends on three camera settings, one of which is aperture.

You can imagine aperture as a “hole” in the lens. It can open allowing more light to come into the camera and it can close and become as little as a hole. The aperture setting is indicated by the f-number or f-stops – the larger the f-number, the smaller the aperture. For example f/22 – is a “small” aperture – it means that the camera lens is almost closed preventing so much light from entering; f/8 – is a “medium” aperture – not so small and not large; f/2 – is a “large” aperture – it means that the lens is opened allowing more light to pass through the lens. 

Every lens has its limit on how large or how small the aperture can get:  there are maximum (lowest f-number) and minimum apertures (highest f-number). The maximum aperture shows the speed of the lens. A lens with an aperture of f/1.2 or f/1.4 as the maximum aperture is considered to be a fast lens, because it can pass through more light than, for example, a lens with a maximum aperture of f/4.0. Lenses with large apertures are better suited for low light photography.

Don’t be overwhelmed by the technical terms and numbers. You’ll understand everything perfectly after trying all the different settings.

 Thank you for reading!

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