Jim Gollan @ OCA Art of Photography

Saturday, 16 March 2013

Time of Day - Light Throughout The Day (4.3a)

Requirement

12 images, 1 scene at regular intervals

Purpose

To study how the quality of light changes throughout the day
To practice the essential skill of judging how light and shadow will move over a scene

Technical Learning

The movement of the sun during the course of a day creates options for using the changing quality of light, especially in the early morning and late afternoon or evening

Exercise Instructions

Choose a bright sunny day (or bright parts of different days)
Select a scene with a definite subject which will catch the sunlight even when the sun is close to the horizon
Shoot this scene from dawn to dusk
Take at least one image per hour, more during the start and end of the day when the light is changing faster
Use the same composition for each image
Visit the scene before the day of the shoot to establish the requirements of the exercise. You need to work how light and shadow will move during the course of the day, taking into account that shadows lengthen as the sun falls
Decide what the ideal light conditions will be
Which image do you prefer?, which was the best moment? is this the moment you thought it would be?, if not, why not?

Images and Review

How I came to shoot this
I doubted if circumstances would ever allow me to do this project as instructed. Finding a sunny day largely free of commitments as well as a scene that was both suitable for the exercise and accessible seemed improbable. Then on a holiday I found the balcony of my hotel room offered a view almost due north of La Concha, a mountain in Andalucia (if I leaned out slightly). As it was mid March, the day was almost 12 hours from sunrise at 7.30 to 19.20. The forecast was for a sunny day after several of mixed weather. Now or never. Go for it!

I also used Golden Hour, an App on my phone to identify the elevation of the sun and its direction to help read what my light source was doing to my subject.

Images

07.35 - Sunrise
Tip of mountain caught by emerging light,
largely just a shape against the blue sky

Elevation of Sun - 1 º (above horizon)
Direction of Sun - 93 º (almost due East)

07.45
A little more detail revealed...

Elevation of Sun - 3 º

08.00
And so on..
Trees in foreground are now strongly lit,
weak golden light

Elevation of Sun - 5 º

08.15
Details of the mountain structure are starting emerge
as highlights against the dominant shadows

Elevation of Sun - 8 º

08.30
And so on at pace...

Elevation of Sun - 11 º

08.45
Passing cloud steps in between subject and
sun on its journey from East to South,
Much detail lost for the moment

Elevation of Sun - 15 º

09.00
Details of contours starting to emerge
from the shadows

Elevation of Sun - 18 º

09.30
And so on...

Elevation of Sun - 23 º

10.00
Becoming less contrasty

Elevation of Sun - 29 º

10.30
And so on...

Elevation of Sun - 36 º

11.00
Detail in contours starting to fade as the subject
becomes evenly lit from the front and high in
the sky

Elevation of Sun - 40 º

13.35
Sun at its peak elevation and just past due South,
Strong white light, details of mountain
contours largely bleached out

Elevation of Sun - 50 º

15.15
Little change from previous image
except for shadow of a cloud caught
by sun as its heads from South to West

Elevation of Sun - 50 º

16.30
Shadows of passing clouds add erratic
modelling of the mountain shape

Elevation of Sun - 32 º

17.00

Elevation of Sun - 27 º

17.30
As the sun moves west and falls, the shape of
of the mountain starts to re-emerge with
the arrival of shadow.
Temporary haze reduces intensity of light

Elevation of Sun - 22 º

17.45
Haze passed increasing light intensity,
Modelling of mountain texture continues

Elevation of Sun - 19 º

18.00
And so on...

Elevation of Sun - 16 º

18.15
Strong contrast reveals structure
of subject

Elevation of Sun - 13 º

18.30
And so on...

Elevation of Sun - 10 º

18.45
First signs of golden hour as the colour
temperature gets slightly warmer
Modelling of texture continues

Elevation of Sun - 7 º

19.00
And so on...

Elevation of Sun - 4 º

19.10
Intensifying of golden light but stronger contrast
throws deeper shadows onto mountain,
hiding a lot of the detail

Elevation of Sun - 2 º

19.15
Power of light on mountain now a spent force

Elevation of Sun - 1 º

19.20
Sunset, only the peak is now lit,
returns to a shape against the sky

Elevation of Sun - 0 º
Direction of Sun - 268 º (almost due West)

Tuesday, 12 March 2013

Colour of Light - Judging Colour Temperature 2 (4.2b)

Requirement

9 images, 3 daylight conditions x 3 ISO settings

Purpose

To learn how actively to adjust White Balance to manage the recorded colour temperature of an image

Technical Learning

White Balance seeks to adjust any colour cast created in a (digital) camera by the light source(s) so that, for example, highlights appear as 'pure white'
Most cameras have several White Balance settings (e.g. daylight, cloudy, shade, tungsten, flourescent, custom)
In 'custom' mode, the camera allows the photographer to set the colour temperature of the light in Kelvin. At one end of the scale (2000k), lies 'blue', at the other 'yellow' (50000k)

White Balance set at Daylight (5000k)

Blue end of Spectrum (2000K)

Yellow end of spectrum (50000k)

Nevertheless, sunrises and sunsets do not require a white balance adjustment, since the colour cast reinforces their mood

On the other hand, the blue cast of shade often calls for a warmer white balance to make the subject appear more realistic, i.e how the eye sees it

Exercise Instructions

As in the previous project, pick a subject with a neutral colour and photograph it (i) sunlit at midday, (ii) in the shade at midday and (iii) sunlit at sunset
However, for each of these scenes use 3 different White Balance settings: (a) daylight, (b) shade and (c) auto.
Which White Balance setting do you prefer for each of (i) to (iii)?

Images and Review

Used a white plastic face mask against a dark background so that the colour cast from the White Balance settings are more easily seen

Shade at Midday

Auto WB - 5850k
Looks close to white

Daylight WB - 4,950k
Slight blue tinge to mask

Shade WB - 6,050k
No colour cast

Daylight at Midday

Auto WB - 5,250k
Near white

Daylight WB - 4,950k
Rendered white

Shade WB - 6,050k
Slight ywelow cast

Saturday, 9 March 2013

Colour of Light - Judging Colour Temperature 1 (4.2a)

Requirement

3 images, 1 scene x 3 different daylight conditions

Purpose

To appreciate how the human eye sees the colour of light and how the camera records it

Technical Learning

The colours of the rainbow are the visible wavelengths of electromagnetic radiation
Sunlight is our standard for colour and brightness. At midday it looks 'white' (colourless) to the human eye. This happens because the eye mixes all colours to produce white
Light becomes coloured when it is missing part of the spectrum, e.g. at sunset, when sunlight has further to travel through the atmosphere, blue light is filtered out creating a warm colour cast
Daylight acquires colour in two directions
It can become 'warmer' (yellow, orange and red) during sunrise and sunset
It can become 'cooler' (blue) within shade on a sunny day
Changes in the colour of light are graded using a colour temperature scale
They are also more pronounced in reality, i.e. as recorded by the camera, than as seen by the eye (which tends to neutralise changes in the colour temperature of light(

Exercise Instructions

Set the White Balance of your camera to Daylight (vs. Auto)
Photograph an object with a neutral colour in (a) full sunlight at midday (over 40° above the horizon), (b) in shade again at midday and (c) sunlit at sunset on a clear day
Compare the results with your memory of the light conditions

Images and Review

See Project 4.2b

Intensity of Light - Measuring Exposure (4.1a)

Requirement

Part 1 - 4/6 images, each using exposure compensation
Part 2 - 30/36 images, 5 x 0.5EV brackets of 5/6 scenes

Purpose

To learn how to measure and adjust exposure

Technical Learning

Intensity of light

An important skill for a photographer is to isolate 'light' from other elements of a composition
Light has 2 dimensions: (a) intensity (see this section) and (b) quality (see 4.2)
Cameras' exposure meters are designed to work best in normal daylight
The brightness of daylight varies for 2 main reasons: (a) the position of the sun in the sky (itself a function of (i) time of day - see 4.3, (ii) time of year and (iii) latitude of location), and (b) the weather (especially cloud) conditions
At brightness below normal daylight (e.g. indoors or in artificial light) you need to adjust exposure. You can do this in one of three ways, but always at a price: (a) increase ISO, at the risk of raising noise, (b) reducing shutter speed, at the cost of greater motion blur, or (c) widen aperture, at the price of shortening depth of field

Metering systems

Camera metering systems work on the principle of averaging the brightness in the scene and taking this average as the mid tone of the scene, whether or not this is the case. This average is the key around which all other values are set. e.g. in a snow scene the meter will tend to read the whiteness of the snow as neutral grey
Most cameras have three metering methods: (a) centre weighted, (b) predictive and (c) spot
Centre weighted averages the brightness of the central part of the image, so excludes what it is assumes are the less relevant edges of the frame
Predictive examines the brightness values across the scene and anticipates the type of scene based on the data sets stored in the camera. The result varies by the sophistication of the camera make/model
Spot uses the reflected brightness from the chosen part of the scene

Dynamic range and working with metering systems

The camera sensor lacks the dynamic range of the human eye
The key tasks in addressing this limitation is to avoid burning out highlights whilst keeping as much as the desired level of detail in the shadows as possible
This challenge requires making best use of the camera's metering system, either (a) to accept the effect of averaging or (b) to adjust the returned exposure value
Methods to adjust exposure include (a) switch to manual, (b) use the camera's EV compensation tool
Other less direct ways of dealing with the challenge are (a) shoot in RAW and the adjust in the conversion software, (b) use bracketing and either select the best image or blend the images (perhaps using HDR software)

EV compensation guidelines where meter averaging is unlikely to produce the best result

The range of adjustment usually falls between +/ - EV 2.0
The EV compensation required depends on (a) the brightness of the subject and (b) the level of contrast within the scene
In high contrast scenes, use (a) predictive metering and/or (b) exposure to the required treatment of the subject
In low contrast scenes, make the EV adjustment up to the level that avoids compromising the subject

Exercise Instructions

Part 1 - shoot 4/6 images with exposure set purposefully either darker or lighter than average

Part 2 - take 5/6 scenes, each bracketed at intervals of 0.5EV

Images and Review

Part 1 - shoot 4/6 images with exposure set purposefully either darker or lighter than average

Underbelly of the new Blackfriars Bridge

Shot as per meter reading
Detail in the highlights under arches approaches burn out.
This has its merits: it creates the
impression of light flowing through the bridge, it also helps to pulls
eye through the image from dark to light (as do the series of girders and
the tapering perspective)

Minus 0.5 EV
Recovers detail under arches

More London, Workers Walking to Work

Shot as per meter reading
Shadows are too dark, highlights are burnt out

EV plus 1 stop
Reveals some of the detail behind glass and
what is reflected in it as well as of people's backs,
yet strengthen the idea of people walking
towards the white light

Thames Path after rainstorm

Shot as per meter reading
Reflected light burns out the colour of
the paving stones

EV minus 1 stop
Reducing exposure saturates the colour of
the paving stones, without reducing glint
of sunlight on water

Part 2 - take 5/6 scenes, each bracketed at intervals of 0.5EV

Hats

Minus 1 EV
Creates a low key image, which highlights
the expression on the models faces

Minus 0.5 EV,
balances mood of the models expressions
with some of the detail of the hats and faces

As metered
The dullest image in the set

Plus 0.5 EV
Shows most detail of the hat in the foreground,
yet still retains some of the tones on the models

Plus 1 EV
Creates a high key image,
brings out the detail of the background hat
(in other images this sits in the shadows)

Thursday, 7 March 2013

Intensity of Light - Higher and Lower Sensitivity (4.1b)

Requirement

At least 12 images, 6 scenes x High/Low ISO

Purpose

To understand the trade-off in low light of using either low or high ISO: desired exposure vs. higher levels of noise

Technical Learning

Most cameras are designed so that they can capture sharply at ISO 100 people walking in average daylight, when handheld (shutter speed of at least 1/125 sec) using an aperture producing acceptable depth of field (say, f5.6)
As light reduces from this level, some adjustment is needed (i.e. ISO, shutter speed or aperture)
Increasing ISO, say from 100 to 400, is an EV4.0 change, enabling either shutter speed to be 4 times faster (reducing motion blur) or aperture to be 4 times narrower (lengthening depth of field), or some combination of both
However, the price for using higher ISO is the increased risk of noise

Noise

It is a sampling error where less than an ideal level of light reaches the sensor producing a random pattern of aberrant pixels, typically of varying brightness (luminance) and colour (chrominance)
It is usually most evident in areas of continuous tone and deep shadow
Its impact depends on the size at which the image is viewed, i.e. the larger the more noticeable it becomes
It is the opposite of 2 other effects: 'blooming' (flare around blown highlights) and chromatic aberration (highlights with either a red-cyan or blue-yellow fringe)

Exercise Instructions

Shoot 6 scenes first at ISO 400/800 where motion and/or depth of field may be at the margin of acceptability, then shoot the same scene at ISO 100. What impact did the higher ISO setting have?
Examine areas of flat tone and deep shadow in each image for signs of noise in close-up
Consider to what extent noise matters in these images

Images and Review

Used the spinning wheel of my wife's bicycle in the dimly lit garage to conduct this test.

Lumix DMC G3