Project The intensity of light

Exercise: Measuring exposure

This exercise consists of two parts. The first part is to produce photos which are either over – or underexposed and to explain why.  Adjusting the compensation bracketing can lighten or darken an image to achieve something more acceptable to the eye. The second part is to take 5 – 6 pictures of any subject and each one with 5 different exposure values (increasing and decreasing by 0.5 stops arranged around the best exposure).

Part one, a deliberately lighter or darker than average image:

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Nikon D90 at 105mm, ISO 200, 1/30 sec at f5.3

This first picture was taken at +2 stops (overexposed). If I had taken it at the best exposure as measured by the meter the colours and textures of the bird feeder would have been too dark and it would have been impossible to determine colour on the bird itself.

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Nikon D90 at 60mm, ISO 200, 1/1500 sec at f4.8

In this exposure I wanted to silhouette the foreground and bring out the colours and depth of the late afternoon winter sky. A ‘normal’ metered exposure would have blown out the sky and hence a -1.5 stop (underexposed) image.

Part Two: photographs taken around the best ‘measured’ exposure: left to right -1.0, -0.5, 0, +0.5, +1.0

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Nikon D90 at 400mm, ISO 800, 1/350, 1/250, 1/180, 1/125, 1/90 sec at f5.6

My preference is the +0.5 exposure (enlarged) for the truer colour tones of the grasses.

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Nikon D90 at 48mm, ISO 800, 1/3000, 1/1500, 1/1000, 1/750, 1/500 sec at f4.5

My preferred exposure is the -0.5 (enlarged) which represents a truer colour and texture of the stone.

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Nikon D90 at 40mm, ISO 400, 1/400, 1/300, 1/200, 1/100, 1/75 sec at f4.5

A difficult exposure to get right due to the constant grey colour and relatively dark exposure, however my preferred exposure is the +0.5 (enlarged) which shows a sharper and truer colour of the wing mirror.

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Nikon D90 at 62mm, ISO 800, 1/2000, 1/1500, 1/750, 1/500, 1/350 sec at f4.5

The first two underexposed images are too dark and create a slight silhouette effect which I did not want. My optimal exposure is the +0.5 (enlarged) which shows a truer colour of the sky and foreground as well as the buildings.

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Nikon D90 at 400mm, ISO 800, 1/1000, 1/750, 1/500, 1/350, 1/250 sec at f4.0

In this case I have 2 images that would be acceptable, the +0.5 (enlarged) as well as the ‘correct’ exposure per the camera meter.

All in all an interesting exercise which does prove the need to take a series of different exposures of the same picture (bracketing). I have always been aware of the need to do this but in realty have rarely used this technique. This is now something I will consider more carefully in the future.

Exercise: Higher and lower sensitivity

The first part of this exercise requires similar shots to be taken at ‘normal’ and ‘high’ sensitivity. The situation chosen should be marginal; that is, where the mixture of light level and subject movement or depth of field is only just possible. The first shot is taken at normal sensitivity (ISO 100 or 200) and the second taken at a higher sensitivity (ISO 800 or 1600).

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ISO 100 @ 0.5 sec f19.0      ISO 800 @ 1/15 sec f19.0

Both images taken indoors without flash. The first one at ISO 100 was too slow for a hand-held image and hence considerable blur. The second at ISO 800 produced a faster and more acceptable shutter speed and a sharper image.

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ISO 100 @ 0.5 sec f19.0      ISO 800 @ 1/10 sec f19.0

An exaggerated effect of this evening sunset taken at ISO 100 and 800. Clearly the first image produced too slow a shutter speed however the second was more acceptable at the higher sensitivity level.

 

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  ISO 200 @ 1/20 f19.0        ISO 400 @ 1/45 f19.0        ISO 800 @ 1/125 f19.0         

 

 

 

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ISO 1000 @ 1/180 f19.0

A series of images taken at increasing sensitivity at a small aperture to give a larger depth of field. In order to ‘freeze’ the movement of the car across the frame it was the higher ISO 1000 image that achieved a fast enough shutter speed.

 

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