Fowler diesel 'Peldon' at Amberley museum: like many other dark green railway subjects, bringing outthe detail lightens the colour.

First, the camera's own jpeg, resized to 900 pixels high.
Camera jpeg
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Second, from the raw photo at 0EV : experience shows dark greens turn paler in this proces.
0EV raw
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Third, from the raw photo at -1EV : a bit dark, but let's see what happens.
-1EV for better starting point
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Fourth, add +2EV to "correct" for any shadow detail, so actually +1EV.
+1EV for shadow detail
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Fifth, subtract 2EV from "correct" for any highlight detail, so actually -3EV.
-3EV for highlights
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At last, use the "Three Exposures" filter.
Three Exposures
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Seventh, G'MIC Local contrast enhancement filter.
Local contrast enhancement
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Eighth, the Advanced Tone mapping filter.
Tone mapping
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Ninth, use the curves tool for a bit more contrast, a bit overdone.
Curve for contrast
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Finally, sharpen with the Unsharp Mask.
Unsharp Mask