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Beginners Guide to Photography No.1
One of the most important aspects of photography is exposure. I would define this as the amount of light that hits your sensor or film. As most of you will be working with a digital camera, for ease of reference I will only refer to a sensor.
So we start from the sensor being black. The light then hits your sensor turning it gradually lighter and lighter. To get the correct exposure we need to make sure the right amount of light hits the sensor no more nor no less. If you look at the images of the Iguana above; In the right hand image not enough light has hit the sensor (so is termed under-exposed). The central image has the correct exposure and in the left hand image too much light has hit the sensor (so is termed over-exposed).
So how do we control the amount of light that hits the sensor?
There are two main settings that we can use to adjust the exposure, the time the shutter is open (the speed) and the size of the hole in the front of the camera that lets the light in (the aperture).
Now it is a balancing act of Speed v Aperture to get the correct exposure. If you want to take the picture at a higher speed then you have to make the aperture bigger to let more light in. Conversely if you want to slow down the speed or take with a smaller aperture, then this will require the camera to have the lens open for longer.
So why would we not want our camera to adjust these automatically?
Well there are times, particularly when you want to get the picture quickly when I would use the camera in automatic, however, whenever it is possible I want to dictate to the camera how the photograph looks.
I may want to control the speed of the shutter, as an example, in Sports photography you normally want to freeze the action, so need to take the picture at a higher speed.
Have a look at the images below
Or for something like motorsports you may want to pan the camera in time with the car, taking the picture at a slower speed, so the car is crisp but the background is blurred.
Or you might want motion blur on the photograph to show the movement
Another example of when you might want to take a photograph at a slower speed is when you take moving water in a river or sea., My example is of a waterfall. Notice how the water appears milky white
One consequence of adjusting the aperture (opening) of the lens is that the 'depth of field' changes.
So what is the 'depth of field'? This means the range in distance from you which is in focus.
Without wanting to give you a complex physics lesson, what happens is that when you open up the lens, the distance that is in focus decreases. Conversely, If you close down the lens then the range increases. Here are two extreme examples:
So now would be a good time for you to have a go, so grab your camera.
You got it? Now turn it on and make sure that you have a memory card in it (trust me, not having a memory card in your camera is not too rare but is very embarrassing!
Now it depends on your camera but you should be able to find somewhere quite easily, a dial or menu to adjust the mode that the camera is in (if you cannot find it look in your camera's manual) This dial or menu will have various options including P, A, T(or Tv), A (or Av)
First off turn your camera to A (or Av).
This means that the camera will take care of everything except the aperture of the lens, which you can adjust manually. (this is properly called aperture priority).
Now the size of the aperture is measured in what are called F stops and rather confusingly, the smaller the number of the F stop, the bigger the hole or aperture.
Again you should be able to readily see either on your lens or in a menu on your camera a way seeing which F stop you are currently set on and adjusting it (again refer to your manual if you cannot find it).
I would like you now to dial this to the smallest number available (maybe F2.8, F4 or F5.6, depending on your lens.
Now, when you have done this look through your camera (or look at the back screen) and half press your 'take' button and you will see a series of numbers, one of which will be the F stop you have just dialled in, another will be speed and the third number will be the ISO which we will look into later in the course. Note these number down (by the way this exercise is best done in daylight)
Now I want you to adjust your F stop to the biggest number you can (it should be something like F22 or F32) and again look through the camera and half press the 'take' button and note the numbers.
The two readings I have just noted are:
500 F5.6 100
So that means with this particular lens, I would be taking at F5.6 (lens open) 500th of a second
The second reading is
15 F32 100
This means with the lens at F32 (closed right down), I would be getting a shutter speed of 1/15th of a second.
For your next exercise, I want you to go outside and take a picture of the side of a house or a fence. Stand right next to your chosen object, so it goes away from you.
Something like this:
Now I want you to take the same photo twice. Once with your lens wide open (Small F number) and once with the lens closed down (High F number).
Now have a look (preferably by loading the two images onto your computer or other device) and you should immediately see how much of the subject (the fence or building) is in focus in the picture taken with the lens closed down (higher number).
One final exercise which you can repeat (for ever, as this is a great skill to learn), is leave your camera on A (or Av) and again select your lowest F stop and take a portrait of your nearest and dearest from about four to five feet away. Take this shot with an open background (in other words not in front of a wall or fence). You should get a lovely shot of your subject with the background nicely out of focus. Let me know how you get on with these exercises.
Next time we will learn more about your camera's settings and when to use them.
© 2017 Dave Proctor