Course Notes, April 13, 2009
In class today Professor mimi discussed a bit about a camera and the different sources of noise.
1. Diffracion
- Diffraction is a common problem with small apertures which do result in a higher depth of field but at the same time cause diffraction due to the edges of the aperture window. There are many, many articles on this subject and suffice it to say, different lenses have different optimal aperture settings that give both the maximum depth of field while keeping diffraction to a minimum
2. Lens Geometry
- Edges of Lens
- Shape Imperfections
- most modern high quality lenses have negligible imperfections, however some companies will replace the lens if these imperfections are discovered.
3. Dispersion
- Deals with multi-chromatic lights and differing refractive indexes
- most modern high quality lenses have negligible dispersion.
Most of these sources of noise are on the "Continuous Time" area of the camera. There are also numerous sources of digital interference in camera systems that we didn't get to in lecture but i'll go ahead and point out a few of them that you have actually seen in lab already.
1) A/D Photo Sensor Noise. The process of reading the values from this sensor can introduce noise at high sensitivity. This is particularly the reason why high ISO images have more "noise". 2) Over-exposure is also another source of issues with cameras. This over exposure can cause certain details to become washed out in your image. 3) Image Processor. During image processing errors can be introduced into the image via quantization.
There is a lot more information available online regarding this subject and if you want to really dig deeper into the subject, play with a camera and if you have one with manual settings try adjusting these settings and see the results. --Drestes 22:23, 13 April 2009 (UTC)
