sensors
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Fundamentals From Photons to Counts: What a Raw Number Means
A photosite collects electrons, a converter turns them into an integer, and that integer is all any algorithm ever sees. Measured on eighteen exposures of one scene: the count doubles with the shutter to within a few percent, then sticks near 3875 DN, and the ceiling the file declares is not the ceiling the sensor has.
Fundamentals High Dynamic Range: Merging a Bracket, Then Checking It Against a Meter
Eighteen exposures of a 17-stop scene, merged into one radiance map, calibrated with a single scale factor fitted on one patch, then compared with the colorimeter readings taken in the room. Across all 48 patches (the anchor included) the median error is 0.198 stops, 0.109 across the neutral patches, and every large error is at the dark end.
Fundamentals Image Sensing: What the Number in a Pixel Actually Counts
The unit overview: how a photon becomes an integer, why that integer is a random variable, what the tone curve did to it before you saw it, and how eighteen exposures merge back into light you can put a unit on. Measured on one scene: gain 0.294 DN per electron, a full well near 13,200 e⁻, and a merged bracket that lands 0.109 stops from a colorimeter across the neutral patches.
Fundamentals Quantization: How Many Bits a Pixel Deserves
Lesson 3 of The Image as Data. Rounding to fewer levels costs Δ/√12 of error, and on this camera's mid-tones the formula predicts the measurement to within 6% at 10 bits and within 2% from 8 bits down. Set that error equal to the read noise unit 1.2 measured and the crossing lands at 9.3 to 9.5 bits, so a 12-bit file on this sensor carries about two and a half bits of nothing.
Fundamentals Sensing Colour: The Bayer Mosaic, and What Interpolation Costs
A silicon photosite is colourblind, so a mosaic of filters gives each one a single colour: a quarter red, a quarter blue, half green. Two thirds of every colour image is therefore interpolated, and measured against photosites that actually exist, that guess costs 4.7 DN on a flat patch and 129.9 DN at an edge, twenty-eight times worse where it shows.
Fundamentals Sensor Noise and Dynamic Range: Measuring the Gain You Were Never Told
Read the same photosite three times and you get three numbers. Plotting the variance of a count against its mean gives a straight line whose slope is the sensor's gain: 0.294 DN per electron on this camera, R² = 0.986, a full well of 13,199 electrons and at least 11.21 stops of dynamic range, none of which appears anywhere in the file.
Fundamentals The Camera Response Curve: Why Your JPEG Is Not Proportional to Light
Raw counts are proportional to the light that arrived. The developed file is not: on six neutral patches, a 42:1 ratio of light comes out as 187 against 14 code values. Measured here, the file sits a mean 9.6 code values off the sRGB curve, and the BT.709 curve the developer applied by default accounts for most of that.