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Friday 27 September 2013

Learning to Shoot in Manual: Photography tutorials (Part Two) Exposure triangle

Here it is. The secret to shooting in full manual mode. Three little words, ISO, Aperture,Shutter. When you understand these 3 elements you will achieve optimal exposure.

So let's break it down. Shutter, most of you probably know, is how fast or slow the opening inside the camera opens and closes.When you press the button, known as the shutter button it causes the sensor inside your camera to be exposed to light. If you use very high shutter speeds then it will freeze action whereas if you use slower shutter speeds it creates more blur or softer images. Now why in the world do you want blurry images you ask, or you might say "that's why I'm looking at your blog because most of my pictures are blurry", there is a difference between out of focus and blur. If you look at a photo and everything is blurred then chances are it is either out of focus or you were shaking the camera. When things are creatively blurred then  most of the photo will be sharp, but a section will have blur to suggest movement or speed or softness.

Looking at this photo on the left you see how crisp all the details are except the bus. This is a great example of creative blur. It gives the feeling of motion and speed and the subject is clearly defined with composition (rule of thirds, more on that later) and the crispness of everything else in the frame.

Other examples of longer shutter speeds would be water that looks like mist, or light trails as shown on the right.

Now you cannot just alter the shutter speed alone. If you increase the length of shutter speed like I did, to capture these effects, your photo will come out like a white piece of paper, perhaps with some grey shadows here and there. The reason for this is because there was light coming into the camera for too long and your sensor was filled with light particles. A very good analogy is to imagine the sensor on your camera is a platform covered in buckets, you want your buckets to be filled just to the top. Overfill, and your buckets will leak water everywhere and wash out your photo. Don't fill the buckets enough and your photo won't have enough light and things will be dark to black. So how do you get the buckets filled when changing your shutter speeds so the buckets are filled to jut the right level. That's the other parts of the triangle.

Adjusting aperture gives you the ability to lengthen or shorten shutter speed based on need. Your aperture controls the size of the opening through your lens and therefore the amount of light that is allowed in. Now what is somewhat confusing is that the lower the aperture value, f1.2, f1.8, f2.0 the larger the opening in the glass. Lenses with a lower number f stop such as these are referred to as fast glass, because you can shoot at much faster shutter speeds in lower lighting conditions. If you increase the aperture number to f12, f18, or in the case of the photo above left f22 and on the right f9, you can then slow the shutter speed down considerably because the opening is so small the shutter needs to be opened longer to fill the buckets on our sensor.

Is that the only purpose of aperture, to control the speed of your shutter, of course not. If it was then photography would be much easier and everybody would take breathtaking photos every time. The other purpose to decreasing or increasing your aperture is to create back and foreground softness. If you look at the photo below you can see that just the main subject is in focus and everything behind begins to become softer and out of focus. 

This is one of those creative styles used in photography and especially portrait photos. If you  shoot landscapes or broader subjects where you want everything in focus then using a higher f stop will provide greater focus. These shallow and great focuses are what are referred to as depth of field. A shallow DOF is simply very little area in focus along one distance from the camera. Take for example the the photo above, the focus point on the subject is x feet away and everything in the photo that is that x distance away is in focus and everything else is not. Now look at the photo below, everything in this photo appears to be in focus and will so even if enlarged and that my friends is the simple truth of shallow vs. broad depth of field.


Now to be fair there are other ways to change depth of field using different lenses, prime vs. telephoto, but lets leave that subject for another day. For now I want you to go out and play with your depth of field and shutter speeds. You will discover that one is reflective of the other and both need to be in harmony to achieve a good exposure.

Oh wait what about the third part of the triangle, ISO. Well I think I will leave that to the next post as you have more than enough to chew on for now. ISO while important is not quite as difficult to understand as these other two and once you grasp shutter and aperture ISO will fall quietly into place. So till next time keep playing keep creating and have fun

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