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Exposure Triangle

Remember all those things I mentioned on aperture, shutter speed and ISO. Well put these together and you have the exposure triangle. Manual mode does this sound scary to you. I´ll try and make is a little easier.


How does this all work together? First off put the camera into manual mode (m on the dial).


The camera has an inbuilt light meter. (See below)


Have you seen this on your camera? If not you need to hunt down the manual and find out
why. (Simple p&s won´t have this feature but more advanced cameras with manual options
and bridge cameras should). See the little plus and minus on either side? Minus means
underexposed and plus means overexposed.

The figure on the left shows an underexposed photo, this means not enough light was allowed
in on the sensor, the photo is dark.
The middle figure is what the camera reads to be perfect, but as we all know, we don´t always
want this, that’s why we are learning to shot in manual mode.
And the figure on the right is an over exposed, meaning too much light was allowed in.
(There will be times when you want to override what the camera says to you as perfect)
So point the camera at a subject and press the shutter button half way down. OK so far? Good.
The light meter will show the exposure with the current settings. Check it out, is it over
exposed, under exposed or just about OK?

Let’s say the light meter reads the scene as underexposed. This means you need to allow some more light onto the sensor. You have some options. You can change the shutter speed, you can change the aperture, or you can change the ISO.
Let’s change the shutter speed. In this case the aperture will stay the same, the ISO the same and the shutter speed will change. We are going to use a slower shutter speed. Move the dial so the number becomes smaller. This is measured in fractions or seconds, the larger the number the faster the shutter speed. So, to allow more light onto the sensor move the dial to a smaller fraction of a number or seconds. (Smaller number)
1000 500 250 125 60 30 15 8 4 2 1” 2”, etc.

Has the light meter changed? Is it closer to the centre, if not keep changing the shutter
speed until you are happy. But, now the shutter speed is too slow for handheld, you
can change the ISO to compensate or the aperture to compensate.
Let’s say the shutter speed is too slow for handheld, options, use a tripod, use a wider
aperture or a higher ISO. Keep checking the light meter until you are happy, then take
the photo.
Remember what you want as a result of the photo you take. Depth of field, a fast or
slow shutter speeds? Practice loads this week. Until you get the hang of it, because
once you have, you will never look back.

This information is available as a pdf, click here

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