Digital Photography. For beginners. Week 5

Transcription

1 Digital Photography For beginners Week 5

2 In this session: Constructive Critique Manual & Auto Focus Focal lengths Field of View & Perspective The correct Lens Zoom & Zooming techniques Assignment 5

3 Manual & Auto focusing

4 Single Shot Mode First off, you have the mode that s probably been around the longest Canon s One Shot and Nikon s AF-S. Both of these will do pretty much the same thing. This mode is predominantly used for stationary objects like model shoots (most of the time more on when not to use it for model shoots later) and anything that doesn t require your subject to move around too much in the frame. You half press the shutter in this mode, and then you can recompose the image. For example, you focus on the model s eyes, then recompose to put her on the left hand side of the image, (see Focus & Recompose later). This autofocus mode will get you through most situations. Active or Continuous Focus Modes Next we have the step up from the single focus to Canon s AI Servo, and Nikon s AF-C modes. Essentially what this setting does is to continuously track your initial focus point and readjust the focus accordingly. This setting is ideal for moving subjects like active children, and pets that are constantly on the move.

5 Auto Modes Finally out of the autofocus settings we have Canon s AI Focus, and Nikon s AF- A. Both of these settings actually leave it up to the camera to decide which is best out of the other two focusing modes to use. In this mode it will either choose to continuously track your chosen subject should it decide to move, or focus lock if you would like to recompose. In theory, then I needn t of bothered explaining the other two settings as surely this is the best of both worlds? Not quite. I personally have tested this mode a fair amount with stop-start subjects and although the camera does a good job of keeping up with them it s always more accurate to use continuous focus mode. The same also goes for its ability to determine when a subject has stopped and when to focus lock for recomposing. Personally I never use this mode as although it has the best of both, it also has the worst of both. So, although I have just covered the three basic settings here very briefly, there is, of course, a whole of host other technological advancements in autofocus that I haven t covered. I know Nikon has extensive, matrix and 3D autofocusing features. As well most modern DSLR have incorporated the back button autofocus which also helps with focus locking.

6 Manual Focus Mode The last focus mode I wanted to cover and one that is rarely used is the Manual focus mode. This mode strikes fear into the heart of nearly all modern photographers and that s simply because they ve probably never used it. Do you ever need to use it? That is something that only you can decide and is probably based on the type of photographs you take. If you only ever take portraits of energetic kids or fast paced sports, then autofocus is probably always your go-to mode. If however you shoot still life, architecture, landscapes and other detailed, relatively motionless subjects, then manual focus is probably a good way to go. There are a few reasons for this. Landscape photographers will want to find the hyper-focal distance of their scene to maximise the amount of in-focus points (depth of field) in the image. This is based on an equation so autofocusing on a specific object is not always the way to go. Still life photographers will usually have their camera locked-down on a tripod so they will not want to focus and recompose once they ve set up the shot, so it s just far easier to focus manually. There is also another reason to want to use manual mode on some cameras and certain situations.

7 The diagram on the left clearly illustrates what s actually going on when you recompose an image after focusing in autofocus mode. The actual part of the image that was in focus, is now out of focus. This isn t normally a noticeable problem when recomposing at f/16, but at f/1.8 that dramatic shift in the focal plane means the resulting image is very soft around the model s eyes. There aren t too many ways around this issue, especially as you may not notice it on the back of the camera s little screen. One thing that did resolve it though was by switching to manual focus. I could then compose my shot and manually focus on the model s eyes, resulting in a fantastically sharp image where I wanted it to be sharp.

8 Understanding the Focus and Recompose Technique Digital cameras have an array of squares or dots, that you see when you look through the viewfinder, which represent the points at which it is capable of focusing. Put your subject on top of one of those dots, press the shutter button, and you ll get a nice sharp image.usually. But, sometimes your camera doesn t light up the right dot, or your subject is out of the range of the focus points, or you want to select a specific point but you have trouble moving the buttons, knobs, and dials on your camera fast enough. If this sounds like you, or if you just want to check out a new way of using your camera, you might want to try the focus-and-recompose technique. Focus-and-recompose is a process wherein you select the focus point, often just one single dot or square in your viewfinder, and lock focus with a half-press of the shutter button. Then with a flick of your wrist you physically move your camera back and forth, or up and down just a bit, in order to recompose your shot will still keeping the focus where you locked it. It sounds a bit complicated, but once you get used to this technique it quickly becomes second nature, and is much faster than fiddling with buttons and dials to select a focus point every time.

9 Lenses Focal Lengths, Field of View The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimetres (e.g., 28 mm, 50 mm, or 100 mm). In the case of zoom lenses, both the minimum and maximum focal lengths are stated, for example mm. As focal length changes, the amount of the subject captured by the lens (the viewing angle) also changes. The shortest focal length, or "ultra wide-angle lenses, range from 14mm to 20mm, and are followed by "wide-angle" lenses from 24mm to 35mm, and then "standard" lenses from 45 to 70mm, which are similar to the field of view of the human eye. Next are "telephoto" lenses reaching up to 300mm, and finally "super telephoto" lenses covering focal lengths of 300mm and greater, a total of five groups. Furthermore, different focal lengths also produce varying levels of perspective and depth of field, which in turn have a large effect on the image's expression.

10 Focal Lengths, Field of View

11 Perspective Perspective refers to the relationship of imaged objects in a photograph. This includes their relative positions and sizes and the space between them. In other words, perspective in the composition of a photograph is the way real threedimensional objects are pictured in a photograph that has a two-dimensional plane. In photography, perspective is another illusion you use to produce photographs of quality composition. When you are taking pictures, the camera always creates perspective. Because a camera automatically produces perspective, many novice photographers believe there is no need to know much about it. This attitude is far from correct. When you know the principles of perspective and skilfully apply them, the photographs you produce show a good rendition of the subject's form and shape, and the viewer is given the sensation of volume, space, depth, and distance. Additionally, the photographer can manipulate perspective to change the illusion of space and distance by either expanding or compressing these factors, therefore providing a sense of scale within the picture.

12 Linear Perspective The human eye judges distance by the way elements within a scene diminish in size, and the angle at which lines and planes converge. This is called linear perspective. The distance between camera and subject and the lens focal length are critical factors affecting linear perspective. This perspective changes as the camera position or viewpoint changes. From a given position, changing only the lens focal length, and not the camera position, does not change the actual viewpoint, but may change the apparent viewpoint. The use of different focal-length lenses in combination with different lens-tosubject distances helps you alter linear perspective in your pictures. When the focal length of the lens is changed but the lens-to-subject distance remains unchanged, there is a change in the image size of the objects, but no change in perspective. On the other hand, when the lens-to-subject distance and lens focal length are both changed, the relationship between objects is altered and perspective is changed. By using the right combination of camera-to-subject distance and lens focal length, a photographer can create a picture that looks deep or shallow. This feeling of depth or shallowness is only an illusion, but it is an important compositional factor.

13 Using a short-focal-length lens from a close camera-to-subject distance, or viewpoint, produces a picture with greater depth (not to be confused with depth of field) than would be produced with a standard lens. Conversely, using a longfocal-length lens from a more distant viewpoint produces a picture with less apparent depth. Rectilinear Perspective Most lenses produce rectilinear perspective that are typical of what the human eye sees. This is to say that lines that are straight in the subject are reproduced straight in the picture. Most pictures are made with rectilinear lenses. Fisheye lenses and the lenses used on panoramic cameras produce a false perspective. A panoramic lens produces panoramic or cylindrical perspective. In other words, all straight horizontal lines at the lens axis level are recorded as straight lines, and all other straight horizontal lines either above or below the lens axis level are reproduced as curved lines. The other false perspective is produced by a fisheye lens in which all straight lines in the subject are imaged as curved lines toward the edges of the picture.

14 Vanishing Point Perspective In vision, lines that are parallel to each other give the sensation of meeting at vanishing points. When parallel lines, either horizontal or vertical, are perpendicular to the lens axis, the vanishing points are assumed to be at infinity. Other lines, those which are parallel to the lens axis, and all other parallel lines at all other angles to the lens axis meet at definable vanishing points. Thus lines that are parallel to the lens axis, or nearly parallel, start in the front of the picture and meet at vanishing points within the picture or at finite points outside the picture.

15 Fast vs Slow Lenses Lenses are marked with their maximum aperture setting. Short focal length prime lenses typically have maximum apertures of f/1.4, f/1.8 or f/2 while telephoto lens are more likely to have maximum aperture settings of f/2.8, f/4 or even f/5.6. High-end, expensive zoom lenses are able to maintain the same maximum aperture setting throughout their focal length range. Less expensive zoom lenses, however, have a variable maximum aperture settings. The kit lenses sold with many DSLRs and compact system cameras often have a maximum aperture of f/ This means that at the widest setting the aperture can be opened up as far as f/3.5, while at the longest telephoto point the maximum aperture is f/5.6. If you set the lens to f/3.5 at the widest point and zoom in, the aperture changes to f/5.6 by the time you reach the longest point. Long lenses with a maximum aperture of f/2.8 or greater and shorter lenses with apertures of f/2 or f/1.8 are often referred to as 'fast' lenses.

16 This is because they allow more light through than their slower counterparts with smaller maximum apertures, and this enables faster shutter speeds to be used. Fast telephoto lenses are therefore very popular with professional sports photographers because the long focal length allows tight framing of the distant subject while the wide maximum aperture enables movement-freezing shutter speeds to be used. Sigma mm f/2.8 EX DG OS HSM AF: This second generation upgrade of Sigma s acclaimed fast telephoto zoom incorporates Sigma s advanced anti-shake system (OS), 2 FLD and three SLD glass elements for optimum image quality and colour correction, anytime manual focus, a minimum focusing distance of 55.1 inches (1:8 max. mag. ratio) and a 9- bladed diaphragm for beautiful bokeh. It s also more compact than its predecessor, measuring only 7.8 inches in length. Price: 1, with kit in Nikon F and Sony Alpha mount.

17 Stabilisation Some lenses have an element inside them that can move to compensate for those accidental movements that are made when we hand-hold a camera. In some cases this stabilisation system has several settings; there maybe one that restricts the correction to vertical movements, for example, which is useful when panning to follow a moving subject. Some image stabilisation systems can also be set to only activate when the shutter release is fully depressed to take a shot. This means that the view through the viewfinder isn't stabilised as it would be normally, but the range of correction available at the time of capture is greater, potentially making it more effective.

18 Prime Lenses In film and photography, a prime lens is either a photographic lens whose focal length is fixed, as opposed to a zoom lens, or it is the primary lens in a combination lens system. Confusion can sometimes result due to the two meanings of the term if the context does not make the interpretation clear. Alternative terms primary focal length, fixed focal length, and FFL are sometimes used to avoid ambiguity. Many lens manufacturers produce or produced prime lenses at or near the following focal lengths: 20 mm, 24 mm, 28 mm, 35 mm, 40 mm, 50 mm, 85 mm, 105 mm, 135 mm, 200 mm, 300 mm, 400 mm, and 600 mm. For these lengths many manufacturers produce two or more lenses with the same focal length but with different maximum apertures to suit the different needs of photographers. Additional focal lengths can be created by using a teleconverter.

19 The Correct lens for the shot? 14mm 20mm 24mm 35mm 50mm 70mm 135mm 200mm 400mm 600mm Wildlife Fashion Sports Street & Documentary Architecture Portraiture Landscape

20 Zoom & Zooming Techniques A zoom lens is a mechanical assembly of lens elements for which the focal length (and thus angle of view) can be varied, as opposed to a fixed focal length (FFL) lens (prime lens). A true zoom lens, also called a parfocal lens, is one that maintains focus when its focal length changes. A lens that loses focus during zooming is more properly called a varifocal lens. Despite being marketed as zoom lenses, virtually all consumer lenses with variable focal lengths use varifocal design. The convenience of variable focal length comes at the cost of complexity - and some compromises on image quality, weight, dimensions, aperture, autofocus performance, and cost. For example, all zoom lenses suffer from at least slight, if not considerable, loss of image resolution at their maximum aperture, especially at the extremes of their focal length range. This effect is evident in the corners of the image, when displayed in a large format or high resolution. The greater the range of focal length a zoom lens offers, the more exaggerated these compromises must become.

21 Zoom Burst A zoom burst, or zoom blur, is a fantastic photographic effect which is simple, fun and easy to achieve. It involves zooming in or out while you take a photo, causing the shot to blur from the centre outwards, as if the scene is bursting towards you. You can use a zoom burst to add movement and action to your photos, and to give them an abstract quality. How to take a Zoom Burst photo You don t need any fancy equipment to get started with zoom bursts - just a DSLR with a zoom lens and an optional tripod. Start by mounting your camera on your tripod. We ll be using a long shutter speed so this will help keep the blurry lines straight. If you don t have a tripod you can stand your camera on a wall or lean against a tree. You can even hand-hold your camera if you don t mind a slightly wobbly feel to your photo - this can actually look really good, so give it a go.

22 Select shutter priority mode and choose a shutter speed of around 1 to 4 seconds. Zoom fully in and focus on your subject. If your camera allows it, lock the focus and exposure at this point, so you know they ll be correct when the subject is filling the frame. Now zoom right out to the widest angle you want to capture. Press the shutter button and zoom in until the subject fills the frame again. Try to zoom as smoothly as possible, maintaining a constant speed throughout and finishing just before the end of your exposure.

23 Assignment 5 Documentary Documentary Photography is a narrative or story being told through photographs that involves real events to provide a factual record or report (and sometimes this is complimented with text). Portraiture, social documentary, documentary landscape, photojournalism, live events, street photography, self portraiture, sports photography, forms of identification, editorial and many more For this assignment you are required to document an event of some kind, be it something simple as a flower dying in a vase or covering an event such as, a demonstration, Birthday Party or something news worthy. You need to take between 5 & 7 images, each of your documentary s must have a Beginning a Middle and an End. No s are: Candles Burning Down or Matches, Making Breakfast and eating it, or, Making Cakes. You have 2 weeks to complete this assignment as next week is half term.