Camera basics

Inside a camera

Inside a camera exists a lens, and aperture, a sensor, a shutter and a mirror system (although modern developments mean that a camera does not always require a mirror system and a live feed through the lens is shown in the viewfinder and on the screen).

The aperture is the hole behind the lens that lets the light inside the camera to hit the sensor and create an image.

The lens sits in front of the aperture, focusing the light through the hole, onto the sensor.

The sensor absorbs the light, creating an image inside the camera.

The shutter opens and closes the aperture, controlling the volume of light that gets let into the camera.

The mirror system consists of two mirrors at 45 degree angles inside the camera, reflecting the view through the lens into the viewfinder, allowing the photographer to preview the image and compose as desired.

The exposure triangle

For the correct exposure of an image, you must consider three things: aperture, shutter speed, and ISO (ASA for film cameras).

The aperture is the size of the hole that lets the light in to the camera. The larger the hole, the more light that gets let in. The aperture also controls the depth of field. The larger the hole (the smaller the F number) the shallower the depth of field . This is due to the physics of the way that light moves.

The ISO is the camera sensor's sensitivity to light (or the film's sensitivity to light in a film camera - ASA). The higher the ISO, the more sensitive the sensor and therefore the more light is sees. The ISO is also responsible for noise (grain) in the image. The higher the ISO, the greater the noise.

Finally, the shutter speed denotes the length of time that the camera's shutter is open for. A longer shutter speed will let in more light, whilst a shorter shutter speed will let very little light in. However, the longer the shutter speed, the more likely it is that the image will experience motion blur of the subjects or blur due to camera shake.

In this image, I wanted to capture a high speed movement and thus I had to prioritise my shutter speed, making it fast enough to only capture a single frame and not show any motion blur. Because the shutter speed was so fast, (1/250)
it did not let a lot of light in and therefore I had to compromise on the other two parts of the triangle in order to correctly expose the image.

I chose to take this image outside due to the better quality of light, meaning that I did not have to overly increase the ISO (the camera's light sensitivity) and consequently reduced the grain in the image. Here I used and ISO of 160.

For the aperture, I used an F-stop of 4.0 in order to create a shallower depth of field and let the light falloff in the background direct the focus toward the model. I chose this spot to take the photo due to the leading lines of the image, again directing the eye toward the model.

Additionally, the downhill slope in the image makes the model appear to have jumped higher and thus makes the image seem more dynamic and exciting. Another little trick I used here was to get the model to kick her heels up behind her, which also makes the jump seem higher.

Furthermore in this image, I exposed for detail in the shadows which unfortunately meant that the highlights in the top left were overexposed.

Here, I wanted to test my skills in low-light photography. For this image, I had to greatly increase the ISO (the camera's light sensitivity) in order for the camera to be able to see the scene. Unfortunately, this increased ISO - 6400 - also meant an increased level of grain in the image.

I still used a large aperture (F 4.0) in order to create a shallow depth of field. This created a nice light falloff in the background which isolated the subject, making her stand out form the darkness.

Also in this image, I used a shutter speed of 1/13 to compensate for the darkness of the overall image. Sadly this meant that there was a degree of camera shake, but I attempted to reduce this by using three points of contact to hold up my camera - making myself into a human tripod - and took the shot on an out breath (meaning that my body was calmer and stiller).

Compositionally, I am happy with this image as I used the rule of thirds to focus the eye on the subject. I covered the left thirds of the image with the red doorframe - creating a foreground interest - and covered the right thirds of the image with the door, effectively framing the subject. Also in this image, I used highlight clipping (exposing for detail in the highlights) meaning that the detail was lost in the shadows. However I quite like this effect as it again isolates the subject, drawing the viewer's eye.

Here I experimented with portrait photography, using a shallow depth of field to blur the background and isolate the subject. The aperture of F 4.0 could perhaps have been lower to create an even shallower depth of field, but I still effectively managed to blur out the background and the nearside of the column in the foreground to distinguish the model.

The large aperture let a fair amount of light in and so I did not need to over-compensate with the ISO. I consequently used an ISO of 160 to lighten up the image slightly, but without producing grain.

Furthermore, the image was already fairly well exposed due to the placement of the model in a lighter area of the environment, and so I did not need to use a slower shutter speed to let more light in. A speed of 1/250 was suitable to capture a well exposed image and avoid any camera shake.

I exposed for the highlights in this image, meaning that the details in the shadows were lost (clipped out). Due to the proportion of shadows in the image, the lack of details makes the whole image appear underexposed. However, a correct exposure is a matter of opinion and thus is quite subjective - I personally believe that the exposure relates to the purpose of the overall image and the effect that it is trying to create. Hence for its purpose as a portrait shot, this image shows the details of the face and is therefore correctly exposed.

Composition wise, I again used the rule of thirds to construct my image. I covered the right thirds with a pillar, creating a half frame for the model, drawing the viewers attention. Additionally, the direct address of this image (where the model is looking directly at the viewer) is enhanced by the fact that her eyes are placed on the top thirds line, drawing our attention.

White balance

This is the original image, taken using the automatic white balance feature on the camera (taken at 1/200 F4 ISO 1000). The ISO was higher than I would've liked, but it needed to be this in order to expose the image enough in the inside conditions. My focus was a little off, the shallow depth of field capturing the far side of the dinosaur as opposed to the near side, however it is a suitable composition and image to experiment with white balance.

I then proceeded to experiment using different white balance settings to observe the effect on the image. White balance in photography is a measure of the temperature of the light hitting the sensor. Different situations have different amounts and types of light, for instance: daylight from the sun is quite white, whereas light from a streetlamp/bulb can be more yellow/orangey. These white balance settings on the camera are specific to certain light types and compensate for the colour of light in the scene to make it seem more natural and accurate to how the human eye sees it.