Basics Of Photography (II)

Now Let us go into technical aspect of photography. One of the first things you will want to get your head around in photography is understanding exposure. A “correct” or good exposure occurs when you maintain as much detail as possible in both very bright parts (highlights) as well as the very dark parts (shadows) in an image. In simple terms, the camera's exposure value settings determine if an image will be too light, too dark, or correctly exposed according to normal standards.

The correct or desired exposure is obtained by using a combination of the lens aperture, the shutter speed and the ISO setting. These three functions are commonly known as the "Exposure Triangle". 

Lets take a look at each of these functions individually, and then how they work in relation to each other. 

The Exposure Triangle

1) Aperture

2) Shutter Speed

3) ISO

1)   Aperture

Aperture is ‘the opening in the lens.’ The size of the lens aperture opening determines the amount of light that reaches the camera's image sensor.

Inside the camera lens is a system of blades which open and close to increase or decrease the opening through which the light passes into the camera.

 Aperture is measured in ‘f-stops’. ie. the various lens aperture settings are called "F Stops". The aperture settings with the lower F Stop numbers allow more light to reach the image sensor than the settings with the higher F Stop numbers. ie. f/1.4 will allow more light then f/5.6 and vice versa. Moving from one f-stop to the next doubles or halves the size of the amount of opening in your lens (and the amount of light getting through).

Now this is very important as most of the new photographers get confused. Please note that large apertures (where lots of light gets through) are given f/stop smaller numbers and smaller apertures (where less light gets through) have larger f-stop numbers. So f/1.8 is in fact a much larger aperture than f/16.

Depth of Field and Aperture

Another important feature of the camera lens aperture is its effect on the Depth of Field in an image. Depth of field is a reference to how much of the image, (subject, foreground, and background) will be in focus. 

Large depth of field means that most of your image will be in focus.  Large dept of field is ( large f number, small aperture, less light) is mostly used for landscapes.

Small or shallow depth of field means that only part of the image will be in focus and the rest will be blur or fuzzy . Small dept of field ( small f number, large aperture, more light) is mostly used for portraits. Or in other words large aperture ( small f number) will decrease depth of field while small aperture (larger f numbers) will give you larger depth of field. While the camera aperture plays a significant part in the depth of field of an image, it is not the only factor. The distance from the camera lens to the subject also plays a part when it comes to depth of field. The closer the camera lens is to the subject, the more shallow the depth of field will be. The further the subject is away from the camera lens, the wider the depth of field will be.The type of camera lens that is used may also affect the appearance of depth of field in an image.

In the above two images the first image has large dept of field. As you can clearly see that the full image is in focus while in the second picture only the glass to the right is in focus. The rest ( other glass and chairs) go out of focus hence the second picture has shallow dept of field.

2)   Shutter Speed.

Just as the aperture affects the exposure so do the shutter speed. Shutter speed is ‘the amount of time that the shutter is open’.  More specifically the shutter speed determines the length of time that light will be exposed to the camera's image sensor. The shutter speed is usually expressed in fractions of a second, although the time can be longer during some exposures.  Those times reflect how long the camera shutter will be open during an exposure. A shutter speed of 1/20^th of a second keeps the shutter open longer than a shutter speed of 1/250^th of a second. A shutter speed of 1/250^th  sec indicates that the camera shutter will remain open for one two hundred and fiftieth of a second when the shutter release button is pressed. A shutter speed listed as 1/2^th sec indicates the camera shutter will remain open for one half second when the shutter release is pressed.  More the time shutter is open more light will pass through and vice versa. ie. in 1/60^th sec more light will pass then 1/400^th sec.

 

Shutter speeds are commonly referred to as fast or slow with some falling into a mid range. A shutter speed of 1/1000^th  second is a very fast shutter speed. A shutter speed of 1/4^th  second is a pretty slow shutter speed. Fast shutter speed is mostly use to freeze the action while a slow shutter speed is used to blur or give a sense of movement in the image.

In most cases you’ll probably be using shutter speeds not less than  1/60^th of a second without a tripod. This is because anything slower than this is very difficult to use without getting camera shake. This is because you must hold the camera steady for longer period. This is mostly for a beginner. Of course by holding your breath and holding your hands tight to your chest you can even take a shot with 1/10^th of a second without camera shake or using a tripod. Alternatively you can always use a tripod and take a shot with low shutter speed as low as your camera permits you without camera shake.

Here in the first picture the action of the mother and child playing with water is being freezed by using fast shutter speed. I used a shutter speed of  1/1250th sec to capture this picture. You can even see the small drops of water that the child splashed with his feet.  While in second picture I showed the movement of water. I took this picture with a slow shutter speed of 1/10th  sec.

     3)   ISO

The final leg of the triangle is ISO. The funny thing about ISO is that it is an acronym but nobody knows what it stands for. It is always just called ISO even though it really stands for International Organisational for Standardisation.

ISO measures the sensitivity of the image sensor.  the ISO rating or number is an indicator of how sensitive a camera's image sensor is to light at specific setting.   The lower the number the less sensitive your camera is to light. 

Changing your cameras' ISO setting will amplify or decrease the image sensors' ability to read light during an exposure.  Lower ISO number settings will require more light  for the image sensor to produce a good image than when the camera is set to a higher ISO number. A camera set to ISO 400 will need less light to produce a correctly exposed image than when it is set to ISO 100. That is, assuming other factors such as the camera lens aperture setting, and the shutter speed setting remains the same. Higher ISO settings are generally used in darker situations to get faster shutter speeds. However the higher the ISO you choose the noisier shots you will get. In a crop sensor cameras the noise or grains starts to appear around 1600 ISO. But its always better to keep ISO number to minimum as possible.

Using All Three Together

The camera aperture works with the camera shutter and the ISO function to produce acceptable images. That is why these three functions are called the exposure triangle.

As you know, the primary function of the camera aperture is to allow more or less light into the camera so that an acceptable exposure can be obtained. However, the camera aperture setting by itself does not produce a properly exposed image. Same way Shutter Speed in isolation from the other two elements of the Exposure Triangle (aperture and ISO) wont produce a properly exposed image. As you change shutter speed you’ll need to change one or both of the other elements to compensate for it.

Mastering the art of exposure is something that takes a lot of practice. In many ways it’s a juggling act and even the most experienced photographers experiment with their settings as they go. Keep in mind that changing each element not only impacts the exposure of the image but each one also has an impact upon other aspects of it ie changing aperture changes depth of field, changing ISO changes the graininess of a shot and changing shutter speed impacts how motion is captured.

At some point in time you might also thing why do you need three tools to control the exposure? Wouldn’t One suffice? The answer is a big NO. Let me explain.

If you want to shoot a girl dancing then the first thing that should come to your mind is the shutter speed. You should have a fast shutter speed could be around 1/600 or more. unless you want to show some sense of movement of her hand or skirt. Aperture and ISO will follow next. As I mentioned above if you want to freeze her action then you need to choose fast shutter speed which means less light. Then if you want to make the background blur you need a aperture of say f1.4 or f1.8 ( lesser the f number more blur you will get) which in terms of light its more light passing in your camera. So you can set your ISO around 100 if its outdoor (daytime). or 400 (indoors) depending on indoor light conditions. Again if you want a sharp background as well then you need higher aperture that means again less light. In this case you will need to increase the ISO little more than the previous one which I mentioned above. But always try to keep ISO as low as possible and don’t cross 1600 for crop sensor cameras.

Same way if you want to shoot a flower on a plant then first thing you should look for is aperture. Your aperture should be less ie. f1.4 or f1.8 so that the leaves etc that is there in the background doesn’t disturb the viewer’s eyes and it focuses only on the flower. Here shutter speed is not very important as flower is not moving. You can keep shutter speed which is comfortable to you I mean you should not have camera shake. It could be around 1/100-1/125. And then depending on the light condition set the ISO. If but keeping ISO to minimum ie in most cases 100 the picture is bright then you can increase the shutter speed. By increasing the shutter speed less light will enter the camera. And anyways increasing the shutter speed won’t affect your picture as your priority is aperture. And of course if there is nice breeze and the flower is dancing to the tune of the breeze then you have to increase the shutter speed.

To conclude each shot has its own priorities and all three tools go hand in hand. Before taking a picture always ask yourself few questions like what you want to show in your picture? What should be your priority shutter speed or aperture? Is there enough light? or what is the light source.? Do you have a tripod? etc etc. After you get answers to all  your questions then only go for the shot. This should happen quickly. Initially you may take couple minutes but it should happen within few seconds.

 Also remember the relation of aperture to light, shutter speed to light and ISO to light. ie  what is the effect on light entering the camera if you increase or decrease aperture or shutter speed or ISO values.