Beginners Guide To Photo Exposure

Dan Eitreim

February 27, 2015

One of the first questions asked by beginners to photography is… how do I get the right exposure for my photographs?

I’m glad you asked! It means that you are willing to take your camera off of the automatic setting and start establishing some creative control.

First of all, let’s define exposure. Exposure is nothing more than the amount of light needed to properly record the image onto the camera’s photo sensor (or the piece of film if you are an old timer like me).

Exposure is based on three key factors. Aperture, shutter speed and ISO. The first two, aperture and shutter speed, deal with the amount of light allowed to hit the sensor. The last, ISO, deals with the amount of light needed.

First – aperture. The aperture is nothing more than a hole in the lens that allows light to enter the camera. The size of the hole is a mathematical function and is written as an f-stop. The function is pretty involved, but think of it like a fraction with a 1 on top. So an f-stop of f-2.5 can be thought of as the fraction 1 over 2.5. F-16 would be 1 over 16.

Like any other fraction, the smaller the bottom number, the smaller the fraction. So f-16 is a smaller hole than f-4. The smaller the hole, the less light that can get in. The larger the hole the more light. There are massive volumes written to explain aperture and how to use it, but that is what it is in a nutshell.

Now for shutter speed. The shutter is behind the aperture hole, so no matter what size aperture opening you have, the longer the shutter is open, the more light gets through. So a fast shutter speed, is only open long enough for a small amount of light to get through. A slow shutter speed is open longer and more light hits the sensor. Easy isn’t it?

ISO – this is a rating from back in the days of film. It is a speed (kind of like the shutter speed). The lower the number – ISO 100 – the slower it is and the more light you need for a good exposure. The higher the number, ISO 400 – the faster it is, which means you need less light.

The tradeoff is that at a lower ISO, you get sharper images and better saturated colors. Higher ISO’s need less light, but tend to be grainier.

All of these options involve various creative aspects. i.e. a slow shutter will let your scene show movement. A faster speed will freeze the action.

The smaller the aperture, the sharper the focus over a wider plane.

They all involve trades that affect the final print and once made will show YOUR creativity! A camera on automatic can’t do that at all. Try putting your camera on manual and do some experimenting, it’s a lot of fun.

To learn more about a great online class, check out – Photography Master Class

For a bit of fun check out – Trick Photography

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