Canon CHDK Ignore boundary peaks [0 – 32], Auto magnify, Show histogram over/under EXP, Log, 1,000, Linear, 10,000, 100,000, 7,500,000, 1,000,000, 6,250,000, 5,000,000

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In this example the image is both over and under exposed (the scene has a very wide dynamic range)

A 10 MP camera might have its Y-axis scaled like this...

	Linear		Log
	10,000,000 pixels		10,000,000 pixels
	7,500,000	“	1,000,000	“
	6,250,000	“	100,000	“
	5,000,000	“	10,000	“
	3,750,000	“	1,000	“
	2,500,000	“	100	“
	1,250,000	“	10	“
	1	“	1	“
Show histogram over/under EXP			Enable [•]	/ Disable [ ]

EXP in on-screen display. If parts of a scene are over or under exposed, then this setting will display “EXP” above the histogram, and a red dot at the end that is exceeding exposure limits.

Ignore boundary peaks [0 – 32]

Another tool for controlling the scaling of the histogram. If you know that your scene will contain large amounts of black or white (e.g a moon shot) you can set how many levels from the left or right edges of the histogram to ignore, if those levels peak in the histogram. This will increase the visibility of the smaller portion of the histogram.

Auto magnify

Enable [•] / Disable [ ]

N.NNx in on-screen display. Another tool for controlling the scaling of the histogram. This option will magnify the Y-axis (vertical) if less than 20% of the histogram area is filled. The purpose of this function is to make the histogram easier to read when there are very tall peaks. This function lies somewhere between the Linear and Log options above. A red dot over a peak indicates that it’s been clipped due to the magnification. The amount of magnification applied is displayed over the histogram.

No Magnification With Magnification