Differences

This shows you the differences between two versions of the page.

--- raw_based_exposure_feedback [2021/02/04 03:46] – create page with copy/paste from forum Audionut
+++ raw_based_exposure_feedback [2021/02/04 06:45] – more formatting Audionut
@@ Line 1: / Line 1: @@
+;#;
+**Magic Lantern RAW based exposure feedback**
+;#;
 Magic Lantern contains a number of exposure feedback features, based from raw data.  This is very beneficial, as regular Canon exposure feedback is subject to picture style, and other JPG based processing.
-[hr]
+{{ https://s1.postimg.cc/6ggsz6boun/Global_draw.png?200|}}
+These features can be found in the Overlay menu. See image ->
-These features can be found in the Overlay menu.
-[img width=300]https://s1.postimg.cc/6ggsz6boun/Global_draw.png[/img]
-They work in both Movie mode and Photo mode Live View, and in the Quick Image review.
+They work in both [[/glossary/#Movie mode]] and Photo mode [[/glossary/#Live View]], and in the [[/glossary/#Quick Image review]].
 In Movie mode Live View, you must load one of the raw recording modules and have it activated for raw based exposure feedback to function.
 In Photo mode (Live View or not), picture quality must be set to raw in Canon menu, and in Photo mode Live View, ExpSim must be enabled.
-[iurl=#Spotmeter][b]Spotmeter[/b][/iurl]
+  * [[#Spotmeter]]
-[iurl=#Histogram][b]Histogram[/b][/iurl]
+  * [[#Histogram]]
-[iurl=#Histobar][b]Simplified Histobar[/b][/iurl]
+  * [[#Histobar]]
-[iurl=#Zebras][b]Zebras[/b][/iurl]
+  * [[#Zebras]]
-[iurl=#dualzebras][b]Dual ISO Zebras[/b][/iurl]
+  * [[#Dual Zebras|Dual ISO Zebras]]
-[iurl=#JPG][b]RAW vs JPG[/b][/iurl]
+  * [[#RAW vs JPG]]
-[hr]
-[anchor=Spotmeter][color=green][size=14pt][u][b]Spotmeter[/b][/u][/size][/color][/anchor]
-[img width=300]https://s1.postimg.cc/7jgia29vlr/Spotmeter.png[/img]
+==== Spotmeter ====
-The spotmeter is a tool used to meter a particular area of the scene.  For instance, you may want to meter a particular area of your scene, as a highlight, a midtone, or whatever.  The raw based spotmeter in ML works in EV ([url=http://en.wikipedia.org/wiki/Exposure_value]Exposure Value[/url]) units, and represents the EV from saturation (overexposure).
+{{ https://s1.postimg.cc/7jgia29vlr/Spotmeter.png?200}}
-Here is a teddy bear, showing the midtone patch metered for a midtone, checking the white level at this metering, and then Exposing to the Right.
+The spotmeter is a tool used to meter a particular area of the scene.  For instance, you may want to meter a particular area of your scene, as a highlight, a midtone, or whatever.  The raw based spotmeter in ML works in EV [[wp>Exposure_value|Exposure Value]] units, and represents the EV from saturation [[/glossary/#overexposure|(overexposure)]].
-[img width=300]https://s1.postimg.cc/77emw8deq7/Spot_Midtone.jpg[/img] [img width=300]https://s1.postimg.cc/8l1609lw5r/Spot_Highlight.jpg[/img] [img width=300]https://s1.postimg.cc/32j1k4ilj3/Spot_ETTR.jpg[/img]
-[hr]
+Below is a teddy bear, showing the midtone patch metered for a midtone, checking the white level at this metering, and then after [[/glossary/#ettr|Exposing to the Right]].
-[anchor=Histogram][color=green][size=14pt][u][b]Histogram[/b][/u][/size][/color][/anchor]
+{{ https://s1.postimg.cc/32j1k4ilj3/Spot_ETTR.jpg?200}} {{https://s1.postimg.cc/77emw8deq7/Spot_Midtone.jpg?200 }} {{ https://s1.postimg.cc/8l1609lw5r/Spot_Highlight.jpg?200  }}
-[img width=300]https://s1.postimg.cc/59xhqkpsa7/Histogram.png[/img]
-The histogram provides a graphical representation of the exposure of the entire scene.
-[img width=400]https://s1.postimg.cc/60vbnmdcwf/Histogram.jpg[/img]
-The colors in the histogram, represent the color channel in the camera (Red, Green, Blue).
+==== Histogram ====
-You will also notice, that ML displays Cyan, Magenta and Yellow.  If you look at the color chart below, you can see that Yellow falls in between Green and Red, and hence, Yellow represents data in both the Green and Red channels.  Cyan being the data from Green and Blue channels, and Magenta being the data from Blue and Red channels.  White indicates data from all color channels.
-The white vertical lines at the rear of the histogram display, represent full stop EV.  So the very right hand side of the histogram represents overexposure.  The first line from the right hand side, represents 1 EV (a full stop) from overexposure, the next line is another 1 EV (2 EV total) from overexposure, and so on.
+{{ https://s1.postimg.cc/59xhqkpsa7/Histogram.png?200}}
-[img width=300]http://upload.wikimedia.org/wikipedia/commons/3/3b/CIE1931xy_blank.svg[/img]
+The histogram provides a graphical representation of the exposure of the entire scene.
-When the scene contains overexposure, the histogram will provide warnings.
+The colors in the histogram, represent the color channel in the camera (Red, Green, Blue).
+You will also notice, that ML displays Cyan, Magenta and Yellow.  If you look at the color chart below, you can see that Yellow falls in between Green and Red, and hence, Yellow represents data in both the Green and Red channels.  Cyan being the data from Green and Blue channels, and Magenta being the data from Blue and Red channels.  White indicates data from all color channels. [[http://upload.wikimedia.org/wikipedia/commons/3/3b/CIE1931xy_blank.svg|Color reference]].
+{{https://s1.postimg.cc/60vbnmdcwf/Histogram.jpg?200 }}
-[img width=400]https://s1.postimg.cc/1e9omxht9r/Histo_Over.jpg[/img]
+The white vertical lines at the rear of the histogram display, represent full stop EV.  So the very right hand side of the histogram represents overexposure.  The first line from the right hand side, represents 1 EV (a full stop) from overexposure, the next line is another 1 EV (2 EV total) from overexposure, and so on.
-The colored circles in the histogram, warn of overexposure in the color channel.  Small circles show a very small amount of exposure, with the circles increasing in size.  When at least 1 % of the pixels of a channel are overexposed, the numbers inside these colored circles, describe the percentage of pixels that have been overexposed in that color channel.  In the above example. 1% of red pixels have been overexposed, 10% of green pixels and 2% of Blue pixels.
+When the scene contains overexposure, the histogram will provide warnings.
-[color=red]Note:[/color]  This information is derived from the downsized Live View stream.  So the percentages reported, may not be an [i]extremely[/i] accurate representation of the actual percentage, but provides useful information nonetheless.
+{{https://s1.postimg.cc/1e9omxht9r/Histo_Over.jpg?200 }}
-[hr]
+The colored circles in the histogram, warn of overexposure in the color channel
+((This information is derived from the downsized Live View stream.  So the percentages reported, may not be an //extremely// accurate representation of the actual percentage, but provides useful information nonetheless.)).  Small circles show a very small amount of exposure, with the circles increasing in size.  When at least 1 % of the pixels of a channel are overexposed, the numbers inside these colored circles, describe the percentage of pixels that have been overexposed in that color channel.  In the above example. 1% of red pixels have been overexposed, 10% of green pixels and 2% of Blue pixels.
-The histogram in ML also contains [url=http://en.wikipedia.org/wiki/Exposing_to_the_right]Exposure to the Right[/url] information.  This feedback show the user how far they can Expose to the Right before overexposing.
-[img width=300]https://s1.postimg.cc/4xiuykuycf/ETTR_hint.png[/img]
+== Histogram ETTR feedback ==
-Take this scene metered with Canon Av mode.
+{{ https://s1.postimg.cc/4xiuykuycf/ETTR_hint.png?200}}
-[img width=400]https://s1.postimg.cc/5movwricfj/Under.jpg[/img]
+The histogram in ML also contains [[/glossary/#ETTR|Exposure to the Right]] information.  This feedback shows the user how far they can Expose to the Right before [[/glossary/#overexposing]].
-Here we are being given feedback that suggests we can push the exposure 1.5 EV (stops) before overexposure.
+In the three images below, on the left we are being given feedback that suggests we can push the exposure 1.5 EV (stops) before reaching overexposure, in the middle the scene has been exposed to the right, and on the right hand side, the scene has overexposure.
-And in the two images below, on the left hand side, the scene has been Exposed to the Right, and on the right hand side, the scene has been overexposed.
-[img width=400]https://s1.postimg.cc/8z7lr4oeov/ETTR.jpg[/img] [img width=400]https://s1.postimg.cc/64exlcg2u7/Over.jpg[/img]
+{{https://s1.postimg.cc/5movwricfj/Under.jpg?200 }} {{ https://s1.postimg.cc/64exlcg2u7/Over.jpg?200}} {{ https://s1.postimg.cc/8z7lr4oeov/ETTR.jpg?200 }}
-[color=red]Note:[/color]  Due to inconsistencies in the original firmware design, determining the correct overexposure point is extremely difficult.  You should be very wary when the histogram reads from -0.4EV through to (slight) overexposure.  There may be some slight overexposure when none is reported, or vice-versa, there may be no overexposure even though some has been reported.  If you know the true saturation value for your sensor at the shot settings, you may wish to use [url=https://builds.magiclantern.fm/modules.html#raw_diag]raw_diag[/url] if you like to nitpick.
+Due to inconsistencies in the original firmware design, determining the correct overexposure point is extremely difficult.  You should be very wary when the histogram reads from -0.4EV through to (slight) overexposure.  There may be some slight overexposure when none is reported, or vice-versa, there may be no overexposure even though some has been reported.  If you know the true saturation value for your sensor at the shot settings, you may wish to use [[https://builds.magiclantern.fm/modules.html#raw_diag|raw_diag.mo]] if you like to nitpick.
 Otherwise, to be certain of no overexposure, target a ETTR hint > -0.4EV.
-[url=http://www.magiclantern.fm/forum/index.php?topic=20579.msg192432#msg192432]Further discussion.[/url]
+[[http://www.magiclantern.fm/forum/index.php?topic=20579.msg192432#msg192432|Further discussion]]
-[hr]
+== Histogram Dynamic Range Feedback ==
 The histogram in ML also contains [url=http://en.wikipedia.org/wiki/Dynamic_range]Dynamic Range[/url] feedback.  This describes the ratio between the reported white level, and the [url=http://en.wikipedia.org/wiki/Noise_floor]Noise Floor[/url] of the camera, and is only very accurate when the image contains overexposed pixels.