These “thermal electrons” give rise to a form of noise called thermal noise or dark current. The heat generated might free electrons from the image sensor itself, thus contaminating the “true” photoelectrons. When taking a long exposure (several second or minutes) the image sensor heats up and even more so if one uses a high ISO. These “photoelectrons” give rise to analogue signals which are then converted into digital pixels by an Analog to Digital (A/D) Converter. When light (photons) strike the image sensor, electrons are produced. I had vulgarised this in the episode Raw vs Jpeg vs Tiff but as a quick recap, an image sensor consists of a matrix of light sensors which convert light into an electric charge. To understand Thermal Noise, let me remind you how the DSLR image sensor works: The Noise we are covering today is the Thermal Noise. Thermal Noise which si the result of a long exposure and is not treated by the standard Noise Reduction tool feature in the software mentioned above.Ĭanon Long Exposure Noise Reduction setting.Standard/Random Noise which is the result of High ISO and can be treated by Noise Reduction tools such as found in Adobe Lightroom, Photoshop, DXO, DPP etc.The two features are completely different as there are 2 types of noise: In our previous episode, we reviewed the In camera’s High ISO Noise Reduction feature. What is the Lon Exposure Noise Reduction feature modern DSL offer built-in?.In this episode, I answer of your questions:
0 Comments
Leave a Reply. |