Functions for Lighting and Angles
Exposure
To take a picture we need to capture the light reflected or produced by an object, the amount of light allowed to enter the lens (aperture) and affect an image is a process and effect called; exposure. In short; the surface of an object reflects/emits the light, the lens focuses the it and the aperture and shutter, allows the light in to the sensor/film which stores the information in the form of an image. The amount of light let through to the sensor/film is controlled by how wide the aperture is set to open.
A good picture needs a balance between the shadows and the highlights, unless for an artistic purpose of conveying or emphasising the lights or shadows (under/over exposure).
Exposure Value (EV) is a combination of three factors; ISO, Aperture and Shutter Speed, and it is controlled by making adjustments to them.
ISO (‘International Organization for Standardization’)
Photography ISO refers to the sensitivity of the photographic medium to light. Originally used for film and later adapted to digital, it numerically describes the ability of the sensor/film to brighten or darken an image.
Lower number of the ISO indicates lower sensitivity to light and can be used in bright outdoor scenes, whereas higher numbers, for higher sensitivity would normally be use in less lit scenes or gloomy weather to ensure as much as the available light can be processed by the camera and allowed into the sensor.
Higher ISO values increase the amount of digital noise in the final image and should be only be used if a desired exposure cannot be achieved with aperture, shutter speed or extra lighting, it should be adjusted in the context of need and kept as low as possible to avoid image degradation.
Meta data
Every digital image automatically stores the information of the way it was created, through meta data we can access information about the settings on the camera as well as the location of lens used. This information can then be used to match the digital (CG) camera to the one used for the live footage, ensuring the closest relation possible between the CG and real-life elements of the final shot.
Aperture
It is a mechanism within the lens itself, that opens and closes according to the settings. It allows a particular amount of light to reach the shutter and later the sensor. It is also known as F-value or F-stop as the letter associated with it is ’F’ for focal. Large numerical value equals a small aperture opening, in turn allowing little light towards the shutter. Respectively; small value = large opening => more light let through.
Aperture values also affect depth and focus of images. The higher the value, the closer the focus point (officially; ‘Field of critical focus’). By changing the aperture, we affect the Depth of Field (DOF), and so; the open aperture decreases and closed one increases the depth of field, respectively creating shallow (subject in focus, background blurred) and deep depth of field (both subject and background in focus). Other than aperture, depth of field is affected by the lens focal length (optical distance of the lens from the sensor, angle of view) and its distance to the subject. A short focal length will result in a deeper depth of field than a long one, which focuses more on a subject, decreasing the depth of field, and the closer the distance to the subject – the shallower the depth of field.
Shutter Speed
Shutter speed is the exposure time, the length of time the camera shutter is open, allowing the light in, and exposing the sensor creating the information that is later stored as pictures. It is measured in seconds (except B – bulb [shutter release held] and T – time [shutter opened and closed by pressing the button]), and so, ¼ means a quarter of a second and so on.
The shorter the shutter remains open the less light is allowed in but the movement is clean and sharp, whereas when the shutter is open for longer time, the images get brighter but the movement gets blurry, i.e., a running person would be photographed on shorter shutter speed than traffic, that intends to capture the motion of the subjects in the frame (both emphasize motion, but one freezes it and one highlights the path of the movement).
While shooting stills, there is no limit, any shutter speed is allowed depending on the need of a scene, however in cinematography, filmmakers work with a fixed shutter speed value, dictated by the standard frame display length (Frame rate, fps). Standard for web videos and films is 24/25 fps, for TV or sports, it is 30fps and 60fps and up is used for slow motion.
Full Frame sensor and Crop sensor
A crop sensor is smaller than the standard full frame one, which in practice means a tighter field of view (edges will be cropped to focus on the central part) which in practice mean that a 50mm lens is used on camera using a crop sensor with a multiplier of 1.5x, the effect will be as such for which a 75mm lens was used. Full frame cameras offer wider field of view, dynamic range, better low-light and shallow depth of field performance and better detail and resolution in general, however they can get quite expensive and significantly larger in the body as well as file size. Whereas crop sensors are better at photographing more distant subjects, perfect for sport events or wildlife photography, they are more affordable and easier to handle due to their smaller sizes, they do however carry the consequence of lower quality, as the sensor is smaller and allows less light in (compromises have to be made in terms of higher ISO etc.). They also decrease the focal length, as you are ‘zoomed in’ so to say, and for wide angle photography a relatively wide-angle lens would need to be used, which can distort the image quite a bit.
Lens
Lenses focus the light towards the sensor by means of refraction, they are also known as focal length, which refers to the distance between the point of light entry and the photographic medium such as sensor. Main factors controlled by lens types are angles of view (extend of the scene captured) and the image distortion. The shorter the lens – the wider the angle and the more distortion, and respectively; the longer lenses = narrower angle of view and less distortion.
– Fisheye Lens – 7 – 16 mm, ultra-wide-angle lens producing very high distortion, meant for panoramic, hemispheric images or bending a horizon line.
– Macro Lens – short focal length camera lens designed to focus on a tiny detail, allowing more than life size magnification of the element photographed.
– Wide-angle Lens – 10 – 42 mm, for capturing a broad landscape or a large group of subjects, wide angle of view at the cost of increased optical distortion.
– Standard Lens – 50, 85 or 100 mm, great for portraits, live events and still lives, most commonly used lens as it is the closest imitation of what human eyes perceive, it produces very little distortion.
– Telephoto Lens – 100 – 800 mm, magnifies the subject and narrows the field of view, very far range at a cost of shallow depth of field, it also compresses the space perspective.