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Digital Photography Part 3 Creative control
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Digital Photography

Jan 22, 2016

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Digital Photography. Part 3 Creative control. What are creative controls?. The key factors that decide how a composition will look: focusing white balance shutter speed aperture focal length - PowerPoint PPT Presentation
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Page 1: Digital Photography

Digital Photography

Part 3Creative control

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What are creative controls?

The key factors that decide how a composition will look:

• focusing• white balance• shutter speed • aperture• focal lengthCameras can set these automatically (except

focal length), but learning how to use them manually helps in getting great pictures.

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Shutter speedShutter speed is one of the 2

factors that determine exposure. Shutter speed is the time interval during which the shutter is open and the sensor is getting light. For every full stop, the amount of light on the sensor is (about) doubled/halved.

Reasons to set shutter speed manually:

• avoid camera shake• freeze movement• blur movement• panning• increase/reduce depth of field

The standard shutter speeds:… 1/30 sec

4 sec 1/60 sec

2 sec 1/125 sec

1 sec 1/250 sec

1/2 sec 1/500 sec

1/4 sec 1/1000 sec

1/8 sec 1/2000 sec

1/15 sec …

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Effect of shutter speed

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Steady shootingWhen shutter speed is low,

camera shake may blur the image. Its effect can be greatly reduced by holding the camera correctly.

Hold the camera firmly with both hands. Stand with your feet slightly apart. Hold your elbows close to your body. Squeeze the shutter button gently. Get additional support from knees, walls, ledges…

Experiment what works for you. More good tips here:http://knol.google.com/k/vesna-kozelj/how-to-hold-the-camera-with-your-hands/3k0expg5xjecw/2#

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Freezing movement

For freezing movement, you need a fast shutter speed. But how fast? It depends on how fast the subject is moving across the frame – not the actual speed! Distance to the subject also counts. Subjects moving towards or away from the camera need slower shutter speed than those moving across the frame. Also: for close subjects, you can use a flash – it almost always freezes the movement.

Subject Speed Distance

efl

across

Direction of

motiontoward

diagonal

car 80 km/h 30 m 100 mm 1/1000 sec

1/250 sec

1/500 sec

train 160 km/h

50 m 35 mm 1/500 sec

1/125 sec

1/250 sec

jogger 10 km/h 5 m 100 mm 1/750 sec

1/180 sec

1/300 sec

jet plane 800 km/h

2000 m 400 mm 1/500 sec

1/125 sec

1/250 sec

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Effect of freezing movement

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Blurred movement

Fast shutter speeds sometimes fail to convey the dynamism of a moving subject: a speeding car may look just like a parked one. Choosing a slow shutter speed blurs the movement, which may work better. Shutter speed shouldn’t be just slighly slow (blur without the artistic effect) or too slow (image may be unrecognizable). Rule of thumb: 4 stops slower shutter than what you would use for freezing the action.

Panning: tracking a subject with the camera, using slow shutter speed, causing the subject to remain sharp and background to blur. Technique:

• hold the camera steady with two hands

• swing your shoulders from your waist, without moving your feet

• leave more space in front of the moving subject than behind

• follow the subject across and press the shutter button smoothly

• take lots of shots to get a few that work

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Blurring

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Extended exposuresIn low light, exposures of more than 1

second may be needed. Some tips:• Support the camera.• If the camera is supported, you are

free to choose any shutter speed. Choose shutter speed/aperture to suit your needs.

• Choose the lowest ISO setting to minimize noise.

• Use self-timer/shutter release cable/remote control to fire the camera.

• Avoid the widest aperture settings to maximize image quality.

• If you can’t get a slow enough shutter speed, use a neutral density filter.

• Low-light shots tend to be overexposed by the camera; correct for that or use manual exposure.

Camera supports

• whatever you find

• beanbag

• unipod (monopod)

• tripod (pan-tilt head, ball-and-socket head)

telescopic legs

center column

handle

head (with camera platform and quick-release shoe)crank

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Effect of extended exposures

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Depth of field

In principle only objects at a given distance from the lens are sharp – everything closer or further away are blurred to varying degrees. The blur is invisible for a given range of distances around the focusing distance, so everything within that range looks sharp. This range is called the Depth of Field (DoF). Depth of Field depends on a number of factors.

Factors determining DoF:

• aperture: the smaller the aperture (higher f-stops), the more the DoF.

• focusing distance (subject distance): the farther away the focus is, the more the DoF.

• focal length (zoom setting): the shorter the focal length (=wide angle) the more the DoF.

• “circle of confusion”: how big a circle you are willing accept as “point”. Subjective! It also depends on image magnification and how closely it is viewed.

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Depth of field: aperture effect

7.4 mm focal length (35 mm efl), focus on red die

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Depth of field: focal length effect

focus on red die, f/4.0

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Depth of field: focusing distance effect

efl 65 mm, f/3.2

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Depth of field: size matters

Is the yellow die sharp? It depends on the magnification and yourdefinition of “sharp”.

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Maximizing depthUse the controls

together to maximize DoF: use wide lens/zoom setting, close the aperture, get further away from the foreground elements. Multipoint autofocus helps.

The through-the-lens (TTL) viewfinder of bridge and SLR cameras may give an idea of DoF.

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Minimizing depthThrowing things out of

focus is usually much more difficult on digital cameras – SLRs rule here. The main things you can do:

• use long telephoto• use wide aperture• get close to subjectWhy? Keeping parts of the

picture blurred can help concentrate on the main subject and can result in more powerful pictures.

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More DoF tips

DoF in close-up photography isextremely narrow – fight it or use it to your advantage

focus

DoF<1 cm!

Bokeh: out-of-focus backgroundwith smoothly blurred highlights

when taking pictures ofpeople or animals, alwaysfocus on the eyes! Wetend to look at them firstand blur is the most annoying when in the eyes

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Aperture and lens resolution

In several picture-taking situation, more than one shutter speed-aperture combination yields a shake-free picture and enough DoF. In that case, you can take one other factor into consideration: lens resolution.

Lenses provide their best resolution at their mid-apertures. Wider settings decrease resolvable detail because lenses work better optically near their center than their edges. At small apertures, diffraction on the edges of the aperture itself causes another drop in image quality. Quality decrease due to diffraction is worse for smaller sensors. Thus, SLRs can use narrower apertures (typically f/22) before diffraction becomes significant than zoom compacts (typically f/8) or bridge cameras (f/11).

Bottom line: use a mid-aperture setting whenever you can.

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Focal lengthChanging the focal length of

the lens by zooming changes the angle of view of the camera. This is a very important compositional tool:

• useful for cropping when taking the picture

• allows you to maximize sensor effectiveness

• changing it together with the subject distance, it gives more flexibility in choosing background

• allows you to take very different types of shots.

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PerspectivePerspective is the optical

effect that makes distant objects appear smaller than close ones and parallel lines seem to converge. It gives vital clues about depth in the picture.

Perspective depends only on the distance! But using different focal lengths can change the picture because telephoto lenses are used from further away – and that changes perspective.

same perspective!

different perspective

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Manipulating the background

Whether using wide-angle or telephoto lenses, you can end up with very similar-looking pictures. What can change dramatically when you change focal length (and subject distance) is what is in the background and how it looks (DoF, perspective…).

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Wide-angle lensesWide-angle lenses

offer a wider field of view than our eyes. Uses:

• fit a lot of things into the frame

• exaggerate foreground

• create a wide DoFProblem: barrel

distortion

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Telephoto lensesTelephoto lenses offer

a narrower field of view than our eyes. Uses:

• bring distant objects “closer”

• “compress” distances between objects

• create a narrow DoFProblem: heavy,

magnifies camera shake