A Simple Guide to Exposure in Manual Mode

lanterns, darkWhen you start using manual mode on your DSLR you first need to know about the ‘exposure triangle’, which is the shutter speed, ISO and aperture. These three all have an affect on the exposure or brightness of your image and all three can be changed in manual mode, while in aperture priority only the aperture can be changed, and in shutter priority only the shutter speed can be changed.

The Aperture

The aperture is a setting you should be changing whichever mode you’re using, and it has a huge effect on your images, and can cause everything to be in focus or only one point to put it simply. Aperture on a camera is measured in f stops, and the smaller the number the wider the aperture is which is good for focusing on single object close to the camera and blurring the rest of the image which is useful for portraits. On the opposite end higher f numbers are good for landscapes and distant subjects and should keep everything in the scene sharp.

The aperture is a small hole in your camera that gets smaller and bigger depending on your aperture setting, and this has the effect of increasing or decreasing the amount of light that is allowed onto the sensor. So because less light is allowed in with a narrower aperture this decreases the shutter speed making it slower and so the image will appear darker. But with a wider aperture more light is let through and so the brightness and shutter speed increases.

The Shutter Speed

Shutter speed is basically the amount of time light is allowed through onto the camera sensor, and this is affected by the amount of time the shutters are open for.

Shutter speed is shown as 1/number for fractions of a second and a number followed by ” for seconds. For example 1/250 is a very fast shutter speed equating to 1/250th of a second and this means the shutters are open for a much shorter time allowing less light in which is good for bright conditions. On the other end of the spectrum a shutter speed of 1″ is equal to 1 second which is more suited to dark conditions to avoid underexposure at night for example.

Shutter speeds are best suited for specific situations, for example in sports photography with fast moving subjects, much faster shutter speeds will allow you to capture a freeze frame of the action. For night photography and in dark conditions, much slower shutter speeds of a second or slower will be needed to properly expose the image. Other reasons for using a fast shutter speed is because it helps to remove blur from handshake when holding the camera, slower shutter speeds will emphasize this blur while faster will help avoid this. If you need to use slower shutter speeds then a tripod will be needed to keep it stationery.


ISO is a very useful setting which is really easy to use. It affects the sensitivity of the camera to light and changing this setting allows faster shutter speeds without having to change the aperture. The only downfall to ISO is it increases the graininess of photos and so the quality will decrease, and this happens at higher ISO numbers. The darker the conditions, the faster the shutter speed you’ll need, so higher f numbers should be used in this event, for example in a dark room with minimal lighting an ISO of 800 or above should work well. On the other end if you’re shooting in bright sunlight a lower ISO of 100 to 200 is all that would be needed.

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