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Message: <blockquote data-quote="tdodd" data-source="post: 1693786" data-attributes="member: 55450">Consider it this way.....Firstly, let me define "EXPOSURE" as the actual amount of light that is allowed to reach the sensor, while "exposure" is the more common use of the term to mean the totality of the light as recorded after amplification by the application of an ISO boost.The EXPOSURE that the sensor sees is only influenced by the size of the aperture and the duration that the shutter is open. Changing the ISO does not change how many physical photons are recorded by the sensor. The only thing that changes the real EXPOSURE (the photons collected) is varying either shutter speed or aperture (or the actual light intensity itself).In very non-scientific terms, what you are doing when you keep the EXPOSURE the same but increase the ISO is that you improve the noise performance of the elctronics within the sensor circuitry. Don't ask me how or why, but that's what happens. So if you have room to increase your ISO, without reducing the EXPOSURE to compensate then you will improve your captured signal that creates your actual exposure. Obviously if you go too far you will end up causing overexposure, even if the sensor was nowhere near saturation point, so you don't want to go mad, but if you have room to increase the ISO, without reducing the EXPOSURE then you can and should do it.What would be very bad, for noise, is to increase the ISO and to reduce the EXPOSURE to compensate. So, the best approach is to set the slowest shutter speed you can get away with to control shake/blur, the optimum aperture to achieve the DOF you need, and the highest full stop ISO that you then need in order to expose to the right. There simply is no value in using a lower ISO and ending up with a non-ETTR exposure as a result.</blockquote>

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