Photography 1: The Art of Photography

Project: The intensity of light.
Exercise: Higher and lower sensitivity.

For this exercise I took similar shots at both normal and high sensitivity.  I chose situations that were marginal, that is where the mixture of light level and subject movement or depth of field is only just possible.  I took the first photograph at normal sensitivity, (ISO 200), then changed to a higher sensitivity, (eg ISO 400 or 800).  I looked at the two photographs to see whether the change made shooting easier.  In particular, could the photograph not be made successfully at the lower sensitivity but was possible at the higher setting?

I compared the two images close up (at 100%).  I looked in two kinds of area in the picture, ie those that are smooth, with little detail and neither particularly bright nor dark, and also in the deep shadow areas.  I noted the obvious differences.

The pairs of images are shown below:

5174.jpg; Pentax *istD; 18-55mm lens; F22; 1/6s; ISO 200

5175.jpg; Pentax *istD; 18-55mm lens; F22; 1/15s; ISO 800

5177.jpg; Pentax *istD; 18-55mm lens; F22; 2s; ISO 200

5178.jpg; Pentax *istD; 18-55mm lens; F22; 1/2s; ISO 800

The four images above were taken using a tripod to hold the camera steady and as there was no movement in the images a long exposure time was possible without causing problems.  Therefore the lower ISO number could be used to produce a better image, with less noise.

5203.jpg; Pentax *istD; 18-55mm lens; F4.5; 1/4s; ISO 200

5202.jpg; Pentax *istD; 18-55mm lens; F4.5; 1/10s; ISO 800

The two photographs above were taken with the camera hand held.  The shutter speed of 1/4 second when the sensitivity was set to ISO 200 meant that the resulting image was blurred.  The higher ISO setting of 800 meant that a successful image could be produced by bracing the camera against a solid object.

5206.jpg; Pentax *istD; 18-55mm lens; F11; 1/30s; ISO 200

5207.jpg; Pentax *istD; 18-55mm lens; F11; 1/125s; ISO 800

5219.jpg; Pentax *istD; 18-55mm lens; F9.5; 1/60s; ISO 200

5218.jpg; Pentax *istD; 18-55mm lens; F9.5; 1/180s; ISO 800

5227.jpg; Pentax *istD; 18-55mm lens; F9.5; 1/90s; ISO 200

5228.jpg; Pentax *istD; 18-55mm lens; F11; 1/180s; ISO 800

The above images were taken in very poor lighting conditions with a heavy mist and drizzle.  The images produced using a lower ISO number were markedly less noisy than those produced using the higher ISO number.

What have I learned from this exercise?

Higher sensitivities can be used, by increasing the ISO number on the camera but the resulting images will have more noise.  Close inspection of the image in smooth areas, with little detail and in deep shadow areas will reveal that a marked increase in noise will be present when a high ISO setting is used.

This increased noise level may be acceptable if the photo is to be printed small or if the subject of the photograph is so interesting that the noise is hardly noticeable.