Abstract
Digital cameras span a large range in price and performance. Consumers often focus mainly on the resolution in pixels when shopping for a camera. Of equal importance is the quality of the optics and the exposure response. Digital cameras generally have a linear exposure response, but the amount of noise and the dynamic range vary. It is difficult to obtain quantitative information on these parameters to make an informed assessment. This work explores and demonstrates first-principles methods to measure the exposure response to make meaningful comparisons between different camera models. It also shows how to make the most of a particular camera by measuring its noise level and dynamic range, to understand the limits of its useable ISO amplification. The methods only require a computer and free software to download images and extract their RGB pixel values. The analysis, based on the RGB values, uses standard spreadsheet software. The procedures are therefore accessible to anyone with a digital camera and computer, and will help to reduce speculation in comparing cameras, and help consumers make an informed decision.
Highlights
Photographic ParametersA picture represents a scene by recording the different levels of luminance LV (scene brightness) and colors at different locations
Digital cameras achieve imaging by having a mosaic of pixels, each of which contains a photo circuit that produces a voltage representing the light energy received by that pixel
46 Journal of Analytical Sciences, Methods and Instrumentation were plotted versus TV, which is proportional to the radiant exposure (Equation (2)) to see the exposure response curve (Equation (3))
Summary
A picture represents a scene by recording the different levels of luminance LV (scene brightness) and colors at different locations. The aperture (hole) in the lens through which the light goes controls the illuminance, EV (image brightness expressed by power per unit area). A camera’s shutter opens to let in light for a controlled period called the time value TV ( called the exposure time or shutter speed). LV, AV, and TV together control the light energy falling on the sensor per area called the radiant exposure H ( called the luminous exposure or photometric exposure):. The radiant exposure should remain constant for different AV and TV values as long as the ratio TV AV2 is kept constant. Further background on photographic parameters can be found in [1] [2] [3] and [4]
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