Author Topic: How to view RAW histograms after taking the image?  (Read 5646 times)

Audionut

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Re: How to view RAW histograms after taking the image?
« Reply #75 on: November 03, 2017, 03:29:02 PM »
My question was actually: how do we use 0.1% and 1% or any % values while shooting, considering that we have exposure controls, not %-controls.

If you have 500 pixels that are below 10%, and you want those 500 pixels to be above 10%, how do you move those 500 pixels? 
Hint:  You already have the controls necessary on your camera, and don't need a special % control.

My red for emphasis.
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Midtone level:
- mathematically: median (which is a statistically robust indicator for overall exposure)
- interpretation: if it's too much on the left side (SNR too low), your image is likely too noisy
- how you should act: if it's too much on the left, and you still have clipped highlights, you should consider clipping more highlights or using HDR / dual ISO / change lighting / using a Nikon camera...
- note that you can find it pretty much anywhere in the highlighted range (not in the middle)

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Shadow level:
- mathematically: the value below which you have 5% of pixels (see http://en.wikipedia.org/wiki/Percentile )
- interpretation: underexposure warning on these boxes can be ignored (e.g. if you have clipped highlights and don't know of what to get rid first)
- what you should do: if you see both half-underexposure and overexpoure warnings, you should probably just move the exposure to the left and ignore the shadows; but if you see full underexposure and overexposure warnings, you should think whether you are OK with crushing some blacks / clipping some highlights / trying dual ISO / etc.

The next two posts in that thread then discuss further the midtone (median), and how that midtone can vary in it's exposure depending on the scene.  Where talking the middle point of the exposed pixels.  So 50% of the exposed pixels are below this marked exposure point, and 50% of the pixels are above the marked exposure point.  So an underexposed scene will have the midtone marker move to the left, and an overexposed scene will have this midtone marker move to the right.  Why?

Because in an underexposed scene, more pixels are towards to the left, an in an overexposed scene more pixels are towards the right.  The midtone point (50%) moves with the exposure.

The other percentage points are exactly the same.  Let's think about 10%.  So this means that 10% of the pixels in the image are exposed below this point (the 10% marker on the CDF/Histogram).  In an overexposed scene, or a low dynamic range scene that has been exposed to the right, this 10% marker is likely to fall well above the noise floor of the camera.  All of the pixels have been exposed well.

In an underexposed scene, where you have not clipped the highlights, and the 10% marker is towards the left hand side (near the noise floor of the camera), then this is a clear indication that you should expose further to the right.

In a high dynamic range scene, where you have clipped highlights, and the 10% marker is towards the left hand side (near the noise floor of the camera), then you need to follow the advice in the quotes above.  Either just crush that data to black (in post) negating the noise in those pixels, expose further to the right and clip more highlights, try dual ISO, or buy a Nikon/Sony instead for that scene.  Only you can decide the best course of action, because you decide how to expose the scene based on the exposure feedback presented to you.  There's some pretty nifty code in ML, but the AI isn't there yet, you still need to decide how best to expose the scene, ML can only guide you.


Of course. I am just asking for offsetting the 16383 and the 0 from the screen edges. A thin dotted line can indicate the 16383 and the 0.

Well, 0 is a misnomer.  The black level in Canon's is very close to 2048.  This leaves headroom for proper evaluation of the noise sigma.  The option in rawdigger is subtract black.  This is on by default.  Try turning it off if you want accurate data from the CR2.

In practice Canon's only hit 16383 on fast lenses, when in fast mode.  So there's likely to always be an offset on the right hand side.  And it looks to my eyes like there is already some offset on the left hand side.  Why do you need some offset on the left hand side anyway.  Is the idea to waste valuable space?  At ISO 100 (best case scenario), the bottom three stops are useless anyway.  Do you really need to know what's going on there, apart from, those pixels in that area are unusable.  If you need to know how many pixels are in that area, use the % indicators.


I know that. But while shooting (especially outdoors or in bright environment) pixel peeping to evaluate the color of a thin line on a small LCD is hardly the best usability. Evaluating shape is much more straightforward. Hence the suggestion (and the whole discussion about being able to evaluate histogram shape as a human, not just heuristically).

Pixel peeping on a small LCD is not the best usability, period.  Maybe go see an eye doctor.


Don't you think my sketched suggestion would be much more readable and optimal for a small screen space?

No, I don't.  I would wonder why the red channel is brighter then the green channel.  The Red channel is around 50% efficient as the green channel, and yet is at some arbitrary level above the green channel in your sketched suggestion.  With the current implementation as shown by a1ex, I can immediately see where each color channel is relative to the others.
It's not an "automatic un-clutter", it's an automatic cluster fuck.


My personal favorite.
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having channel histograms on top of each other makes it a little difficult to say which channels are clipped and which not.......................Please bear in mind that if the image is underexposed the highlights histogram will be simply a flat line

If the image is underexposed, then we don't need to worry which color channels are clipped.  Don't you think.


I should probably add some emoji's in there somewhere, but meh, you don't seem to place much effort in reading the links presented to you.  Tit for tat.  :D

heyjoe

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Re: How to view RAW histograms after taking the image?
« Reply #76 on: November 03, 2017, 07:54:11 PM »
If you have 500 pixels that are below 10%, and you want those 500 pixels to be above 10%, how do you move those 500 pixels? 
While shooting I don't counts pixels or make calculations based on counts. Personally I watch that my light, composition, focus and ETTR. If I see visually (not numerically as a pixel count) an area which is important and must not be overexposed - I correct exposure, obviously.

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Hint:  You already have the controls necessary on your camera, and don't need a special % control.

My red for emphasis.
...
I have already read the post from the link. I definitely didn't read the next posts.
Thanks for the additional explanations. I am not sure if I will ever use that while shooting.

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Well, 0 is a misnomer.  The black level in Canon's is very close to 2048.  This leaves headroom for proper evaluation of the noise sigma.  The option in rawdigger is subtract black.  This is on by default.  Try turning it off if you want accurate data from the CR2.
It is interesting that you are critical about me not reading thoroughly another thread yet it seems you have not read my posts in the current one (e.g. #8) :) But I appreciate the explanations.

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In practice Canon's only hit 16383 on fast lenses, when in fast mode.
Which doesn't make it an impossible value.

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Why do you need some offset on the left hand side anyway.  Is the idea to waste valuable space?
Because the edge of the screen is the border between 2 physically different materials. When you shoot outdoors there are all kinds of reflections and on the edges of plastic they can be even stronger and more obstructing. As someone who has optimized a lot of UI/UX I can say that it is not a good to place important info/graphics in an area with compromised visibility and rely on the viewer to stare harder.

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At ISO 100 (best case scenario), the bottom three stops are useless anyway.
How is that calculated?

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Do you really need to know what's going on there, apart from, those pixels in that area are unusable.
No.

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If you need to know how many pixels are in that area, use the % indicators.
Maybe I will have to get used to that approach.

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Pixel peeping on a small LCD is not the best usability, period.  Maybe go see an eye doctor.
Or maybe kindly consider that one has suggested a UI optimization in order to avoid pixel peeping.

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No, I don't.  I would wonder why the red channel is brighter then the green channel.  The Red channel is around 50% efficient as the green channel, and yet is at some arbitrary level above the green channel in your sketched suggestion.  With the current implementation as shown by a1ex, I can immediately see where each color channel is relative to the others.
Considering that the shape of channel histograms depends on the scene which is shot + the fact that all 4 channels show the same DR when testing, I wonder what you are talking about. I also wonder how this is related to the essence of the suggestion which is about placement and size of UI elements.

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If the image is underexposed, then we don't need to worry which color channels are clipped.  Don't you think.
You are mixing my posts and creating a new post from that with a totally different meaning which I never had in mind. So you are missing the point in what I said and trying to ridicule it based on misunderstanding.

The idea of having separate channel histogram is related to highlights clipping, not to underexposure. And my earlier post explains that having clipped only one or two channels may be ok in certain situations.

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I should probably add some emoji's in there somewhere, but meh, you don't seem to place much effort in reading the links presented to you.  Tit for tat.  :D
I have read every link shared, even the ones which don't answer clearly a question which was asked.

Considering the jabs you like to make from time to time: If you consider my contribution to this thread worthless, disrespectful to the freedom of software or time wasting I am ready to shut up for good and still be thankful to the developers.

Audionut

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Re: How to view RAW histograms after taking the image?
« Reply #77 on: November 03, 2017, 11:43:05 PM »
You display a consistent behavior of quoting tiny parts of other people's posts, to nitpick.  You've been told once already to knock that shit off.


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Or maybe kindly consider that one has suggested a UI optimization in order to avoid pixel peeping.

You're suggestions are kindly considered, always.  The issue, is that you Sir take issue when your suggestions are not implemented, or there is any sort of 'attack' on those suggestions.  Because your ego exceeds your ability by some margin.

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As someone who has optimized a lot of UI/UX I can say



There's nothing wrong with a big ego, when applied correctly the benefits are great.  But you seem to want to waltz into this community and expect a level of respect.
I think the sad part is, that you've been given a level of respect, but that level doesn't fit within the expectations of your ego, so you want to start throwing toys around.

I strongly suggest that you take a few days off, if for no other reason then to show you can have patience.  Perhaps a1ex is already working on your solution, or at least, has decided to try and implement the idea, as time allows.  Remember, ML isn't some multi-national company with thousands of employees, it's coded in the garage with spare time, buy a couple of people.

heyjoe

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Re: How to view RAW histograms after taking the image?
« Reply #78 on: November 04, 2017, 02:41:08 AM »
Audionut, I was trying to collaborate by sharing things from experience with someone who was interested in turning that into ML functionality and it was going quite well for some time. Then you came in the thread with a series of unrealistic demands, innuendos and all the micro trolling which I was trying not to respond to.

I understand that it is difficult for you to accept that you may actually be talking to someone who can share useful suggestions and you would rather abuse him (with a "level of respect"), call his clarifications "that shit" or "big ego" etc. However that is contrary to the idea of communing and the aggression in your latest reply has gone too far.


Thank you a1ex. Great work. Forgive me if I have said anything inappropriate.

Audionut

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Re: How to view RAW histograms after taking the image?
« Reply #79 on: November 05, 2017, 10:38:05 PM »
the micro trolling which I was trying not to respond to.

Well, at least you tried.........right.

I think society is getting weaker by the day.  "I tried" is an excuse I hear a lot of these days.
A firefighter who runs through a burning building, risking life and limb, but unable to reach the person trapped at the rear of the building, that's trying, that's worth consoling.  A keyboard warrior who tries not to press buttons on a keyboard, but fails.........

While you're taking a break, learn to follow the advise of a moderator, and read this.