dynamic range: shadows and highlights
DESCRIPTION
Dynamic Range: Shadows and Highlights. Dynamic Range. If the electron count is below a certain threshold, it is just recorded as black. So if there aren’t enough photons, all the detail in those pixels is lost. - PowerPoint PPT PresentationTRANSCRIPT
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Dynamic Range:Shadows and Highlights
When the photowell is full, a white value occurs. No photons after this are recorded, so all detail for these pixels are lost.
If the electron count is below a certain threshold, it is just recorded as black. So if there aren’t enough photons, all the detail in those pixels is lost.
DynamicRange
![Page 4: Dynamic Range: Shadows and Highlights](https://reader034.vdocument.in/reader034/viewer/2022050821/56816594550346895dd86592/html5/thumbnails/4.jpg)
Large dynamic range: very bright and very dark areas in same scene
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The camera has a limited dynamic range. Thus it can only capture a certain portion of the total dynamic range of the scene.
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Dynamic Range and Contrast Low contrast | High Contrast
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Histogram: plots pixels according to brightness: L-R, Dark-Bright
Low contrast: Most pixels in middle, few very dark (shadows) or very bright (highlights) areas.
Result: Flat, boring picture. No defining characteristics.
![Page 11: Dynamic Range: Shadows and Highlights](https://reader034.vdocument.in/reader034/viewer/2022050821/56816594550346895dd86592/html5/thumbnails/11.jpg)
Histogram: plots pixels according to brightness: L-R, Dark-Bright
High contrast: More pixels toward edge, in very dark (shadows) or very bright (highlights) areas.
Result: Interesting, dynamic picture. Sharply defined characteristics.
![Page 12: Dynamic Range: Shadows and Highlights](https://reader034.vdocument.in/reader034/viewer/2022050821/56816594550346895dd86592/html5/thumbnails/12.jpg)
Histogram: plots pixels according to brightness: L-R, Dark-Bright
Low contrast: Most pixels in middle, few very dark (shadows) or very bright (highlights) areas.
Result: Flat, boring picture. No defining characteristics.However, low contrast can always be edited into a high contrast image
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Low contrast
High contrast
High contrast has caused this area to be completely white, destroying all detail. It is impossible to get this detail back – this is known as a “blown highlight”.
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Low contrast
High contrast
High contrast has caused this area to be completely black, destroying all detail. It is impossible to get this detail back – this is known as a “crushed shadow”.
![Page 15: Dynamic Range: Shadows and Highlights](https://reader034.vdocument.in/reader034/viewer/2022050821/56816594550346895dd86592/html5/thumbnails/15.jpg)
?Crushed shadows
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?Blown highlights
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Red Green Blue
1 1 1
Red Green Blue
5 5 5
Not all “crushed shadows” are actually black
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Red Green Blue
10 10 10
Red Green Blue
50 50 50
As long as pixels aren’t clipped to pure black (or white), detail still exists
Transformation: Pixel value x 10
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Real-world examples
ToolsExposure adjustment-Levels-Curves
Better ToolsSelective shadow/highlight adjustmentHigh Dynamic Range (HDR) blending
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High Dynamic Range (HDR) Blending
Take two images which cover different exposure rangesBlend together for greater dynamic range
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Important side effectRaising shadows reveals noise!
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RAW Headroom
Original
JPEG -4EV adjustment in ACR
RAW -4EV adjustment in ACR
RAW format gives extra dynamic range headroom to restore crushed shadows and blown highlights
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Fill FlashOriginal
Shadows adjustment
Fill flashLow-power flash can “fill in” shadows
Better tones, less noise than shadows adjustment
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Shadows and Highlights
Larger photowells allow a larger dynamic range to be captured
Larger sensors with less pixels => larger photowells
DynamicRange