TAOP - Light - Measuring Exposure

 Light - Measuring Exposure

Part One

Below are 6 images that I've produced deliberately above or below the camera's measured exposure. For this exercise I've set the camera to Aperture priority, which is what I would normal select. I've then adjusted the shutter speed by using a faster shutter speed to make the images darker or a longer shutter speed to make the images lighter.

Whilst its possible to use the camera in shutter priority and adjust the aperture to lighten or darken images this may impact the depth of field.

Image 1

Using f/8 and allowing the camera to meter the church only, it calculated a shutter speed of 1/500. When I metered the sky it calculated a shutter speed of 1/640. I've taken this image using the faster shutter speed if 1/640. The resulting image is of a perhaps slightly darker church but the cloud is not washed out and the shape of the cloud can be seen. This is because the faster shutter speed has allowed less light to reach the sensor.

Image 2

Using f/8 the camera metered a shutter speed of 1/400, I've then metered specifically for the tree and being darker its reduced the shutter speed to 1/250, a slower shutter speed has allowed more light to reach the sensor and has allowed an overall lighter image.

Image 3

Using f/8 the camera has metered which made the sky blow out very slightly. I've metered for the sky then set the shutter speed to a slightly faster speed of 1/250 which has slightly darkened the sky and overall image.

Image 4

With an aperture of f/8 the camera has metered a shutter speed of 1/400 likely as a result of the contrast between the light sky and the dark branches of the tree. I've reduced the shutter speed to 1/250 which has allowed more light to reach the sensor and has lightened the bark on the tree trunk.

Image 5

Again with an aperture of f/8 the camera has metered a shutter speed of 1/125. I've taken the image and looked at it on the camera screen and thought I could darken the tree using a faster shutter speed and create a darker frame for the river. I've used a shutter speed of 1/160.

Image 6

This is an infra-red image taken using single spot metering which I've taken of the sun just before sunset. By metering the sun the foreground hills and trees have been put into silhouette. I've swapped the blue and red channels to create the colour in this image 

Part Two

Each of the following images have a camera measured exposure followed by images 1/2 stop and one stop under exposed and 1/2 stop and 1 stop over exposed. Here I'm using a consistent shutter speed as originally measured by the camera and then setting the camera to manual and using a consistent shutter speed as originally metered and adjusting the aperture

Image Set 1

All taken using a tripod due to the metered slow shutter speed

Average exposed - f/8 at 1/20

Half stop under exposed - f/9 at 1/20

One stop under exposed - f/10 at 1/20

Half stop over exposed - f/7.1 at 1/20

One stop over exposed - f/6.3 at 1/20

Of this set I prefer the image taken 1/2 stop over exposed as the lighter colour of the yellow contrasts well against the darker background. I've made this image bigger so its easier to spot.

Image Set 2

Images in this set have been taken with a camera converted to infra-red with a 665 nm filter, and the final image has had the blue and red channels swapped.

Average Exposed - f/8 at 1/400

1/2 stop under exposed - f/9 at 1/400

1 stop under exposed - f/10 at 1/400

1/2 stop over exposed - f/7.1 at 1/400

1 stop over exposed - f/6.3 at 1/400

Of this set I prefer the image taken 1 stop over exposed as as the cloud structure is more visible. This was an overcast day and infra-red is more often used in sunny bright conditions. However it maybe a feature of infra-red that I consider taking images 1/2 to stop over exposed in future under these conditions.

Image Set 3

I've converted the images in this set to black and white to see how light affects images without colour

Average exposed at f/8 and 1/250

Half stop under exposed at f/9 and 1/250

One stop under exposed at f/10 and 1/250

Half stop over exposed at f/7.1 and 1/250

 

One stop over exposed at f/6.3 and 1/250

In this set I prefer the mono image 1 stop under exposed, as this image in black and white seems to have a greater range of tones. I suspect the average metered image in this camera to perhaps be slightly over exposed to start.

Image Set 4

Average exposed at f/8 and 1/100

Half stop under exposed at f/9 and 1/100

One stop under exposed at f/10 and 1/100

Half stop under exposed at f/7.1 and 1/100

One stop under exposed at f/6.3 and 1/100

In this set I prefer the image 1/1 stop over exposed, since more of the brickwork in the foreground is exposed and the texture of the brick more visible.

Image Set 5

In this set of images I've again used a converted infra-red camera and swapped the red and blue colour channels.


For some reason the swans remained fairly static in this set either through furious paddling or perhaps at the point they were it was shallow enough to stand

Average exposed at f/8 and 1/60

Half stop under exposed at f/9 and 1/60

One stop under exposed at f/10 and 1/60

Half stop over exposed at f/7.1 and 1/60

One stop over exposed at f/6.3 and 1/60

In this set of images I prefer the camera metered exposure as there seems to be a better balance between the exposure of the water, land and sky.

Image Set 6

Average exposed at f/8 and 1/250

Half stop under exposed at f/9 and 1/250

One stop under exposed at f/10 and 1/250

Half stop over exposed at f/7.1 and 1/250

One stop over exposed at f/6.3 and 1/250

Whilst all the images appear a little washed out in this set I think the best image is the one under exposed by one stop; the colours appear more in line with what my eyes saw

Exercise Learning

a) Using a single point for camera exposure readings can allow you to expose exactly for the subject as opposed to an average scene metered reading. Different tonal contrasts within the scene can result in the camera creating an exposure you aren't seeing with your eyes or an exposure you simply don't want

b) Exposure can be controlled in aperture priority and shutter priority. However controlling exposure with the aperture may impact the depth of field subject amount of aperture change / or your visualised image

c) Digital photography is more cost friendly to "hedging" your image bets. In capturing a scene, if time allows making multiple exposures with slight differences may give greater options though it should also be recognised that using RAW files and adjusting the exposure or even adjusting an image's levels also in post processing may allow for the subtle differences to be made. However as always its better to try and get the image right in the camera. 

d) Spot metering within an image can allow the photographer to be creative when creating images. A good example of this is silhouettes, both creating them and avoiding them

e) Bracketing images also allows the photographer greater options and increase their chances of getting the correct exposure. The Photographer always needs to be aware that the camera's sensor sees / captures images a little different from how our eyes perceive the subject / scene