Exercise: Your tolerance for noise

Noise appears on an photograph as a speckled effect, like salt and pepper; it can be black, coloured or bright. This depends on the scene and also the exposure. You can take several precautions to try and prevent noise occurring "the first and most obvious precaution is to use the lowest ISO setting possible. The second is to make use of the camera's noise reduction option for long exposures" (Mastering Digital Photography, Michael Freeman, Ilex, 2008).

The major cause of noise is there not being enough photons of light that strike the sensors receptors. This in turn causes a sampling error.

For this exercise we are to find a situation which fills the following criteria:

• Daylight indoors -as outdoor light is too bright for high ISO settings, too dark would need long exposure times.
• A combination of sharp detail an textureless areas, with some of the textureless area in shadow.

I set up my camera with the tripod so that each image would be as identical as possible, composition wise, so all I need to change is the ISO setting. I set the camera to the aperture priority setting so that the depth of field also stays the same. I experimented with the aperture and found that f4.8 was the best setting, focal length remained at 48mm.

My cameras range runs from 200 to 3200 so I took a photo at each ISO setting.

 

 

Full size at ISO 200.

 

Zoomed in area to compare noise levels.

 

ISO 200

 

 

ISO 250

ISO 320

ISO 400

ISO 500

ISO 640

ISO 800

ISO 1000

ISO 1250

ISO 1600

 

 

ISO 2000

 

 

 

ISO 2500

 

ISO 3200

Conclusion.


I really start to notice noise at ISO 640 quite considerably, although it is possible to pick it up earlier than this but I felt I could tolerate the level. I would not be happy using the full size image past ISO 800 as I feel that the noise level is quite obvious. Comparing the ISO 200 to the ISO 3200 image there is a much greater difference than I was expecting before I began this exercise. I am really enjoying learning about the more technical aspects of my camera as I feel that this is where I let myself down. I am aiming to do much more of my own research, reading around the subjects introduced, than I had done in the previous course as I feel that is the only way I will become more confident and be able to produce better photos.

References.

Mastering Digital Photography, Michael Freeman, Ilex, 2008

http://www.adorama.com/alc/article/12955