Beginner Histograms for beginners ?

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Terry
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Yes
Histograms are as difficult to explain in simple terms, as they are for a beginner to understand.

It is generally thought that they are useful for judging exposure, and in the crudest sense they are. You can instantly see if the exposure consists of too many dark pixels or too many highlight ones, if they are, the graphic will show the graph as bunched up to the left (dark tones) or to the right (highlight tones.)
However these configurations can also represent a perfectly good exposure. As some of the following shots and histograms will show.

In many cameras you can only see the histogram representing the pixels in black and white. In others you can see the pixels representing the red blue green components, which can give you a better Idea of what is going on. I have shown both versions.

In the first diagram I show a typical histogram ranging from some black pixels to some white ones. With the bulk of them in between. The pink column in the centre represents all the pixels of a particular grey tone, stacked one on another as if counting beans.
And this is exactly what the histograms show. That is the total number of pixels of each tone of grey in the image, stacked in columns from left to right. What they do not show is exposure.
histogram-diagram by Terry Andrews, on Flickr

The first image is of an Artillery Sargent taken in about 1954, it is well exposed, but the histogram shows the greatest number of pixels towards the right, this is because those are the tones of the sky and ground which take up the majority of the picture. The Sargent is somewhat darker and is mostly represented by the flattened portion of the graph. Neither the highlights nor the shadows are clipped. (Off the scale). So all the tones are reproduced normally.
hist-A by Terry Andrews, on Flickr

The second shot is also black and white taken in Madrid in 1957. both the photograph and the histogram look very different. Again the peak to the right represents the bright sky and the scorched earth. But this time far more extreme. There are a some pixels right across the scale but they few in number with a small peak in the deep greys. Again neither the highlights nor shadows are clipped. But the highlights very nearly so, in this very high key shot. So again the exposure is correct.
Hist-b by Terry Andrews, on Flickr

The next shot is again different not only because it is in colour but also because it is taken in candlelight, that had no chance at all to fill the vastness of the church. But the exposure was able to show some detail in what it could illuminate. This time the peak represents the vast black area, and the people and candles are represented by the thin black line along the bottom. Again it is the correct exposure to show the scene as it was. Had I taken a long time exposure I could have shown far more detail, but burnt out the candle light, and totally lost the atmosphere. There is no need to be afraid of low key images.

hist-1a by Terry Andrews, on Flickr

The next is a shot taken directly into the light but not a silhouette. It contains a full range of tones from black to near white. It again is correctly exposed. This time the histograms show two peaks one of dark tones and the other of bright tones but with rather fewer middle tones. This sort of shot is perhaps more difficult to expose correctly with out burning out the highlights.

histC by Terry Andrews, on Flickr

The butterfly image is very evenly lit, as can be seen by the background, and is typical of shooting artworks. The histogram in this case is not so much recording differences in light but more the local tones and colour differences in the subject itself. Though it was taken in situ at a university show, I was able to introduce some soft sidelight to emphasise the textures.

histD by Terry Andrews, on Flickr

The histogram of this Autumn show table, is hard to explain in terms of tones, as it is the bright colours that are emphasised in all their glory in the tangled colour histogram. When processing it, I had trouble with the colours clipping, and it was with some difficulty that I managed to retain detail in them all. Never the less the exposure is correct, the problem lay with the extreme colour gamut and saturation.

HistE by Terry Andrews, on Flickr


The last shot of the bright red Jeep also had colour gamut problems in the warm evening light. However apart from the strange colouration in the faces, the exposure just about captures the entire range of tones and highly saturated colours.

hist-F by Terry Andrews, on Flickr

None of these shots display the typically “Correct” histogram nor would I expect them to. However they all span in some fashion the range of tones from dark to light with little or no clipping.
It is more important to try to discover what a histogram is trying to tell you, than try to force it to fit some notion of correct exposure. Most examples of histograms shown to beginners are more simplistic than the ones that I have given, however they are also less representative of real images.

Histogram Addendum
Now that this thread has reached maturity, there are a couple of points that were raised that need clarification.
( I will also add this post back into the OP….. )

@HoppyUK said you claim "What they do not show is exposure" when they absolutely do - that is their main purpose and usefulness.”

Answer:
You can derive no Exposure information or settings from examining a histogram,
Two entirely different exposures and illumination, can show the exact same histogram.
A histogram does not take into account your intent, it only shows the tonal values that you have or are about to capture.
What it does do… is to give you a guide as to where those tone fall, and the direction that you would need to adjust exposure or exposure compensation to centralise those tones or avoid clipping.
It gives you no information about the magnitude or value of those adjustments.
Adjustments can only be made by trial and error and observation of the changed histogram.

The information a Histogram gives in this way, is indeed useful to correcting exposures



@DG phototraining said

Nicely proving what a waste of time histograms are in general use”
and
“They may tell you what is clipped, but only you know if it matters or not, which is why "blinkies" are so much more useful if you follow the ETTR method”


Answer:
Centralising a histogram is especially useful to a beginner shooting Jpegs, who needs to get the image tones pegged, so as that the mid tone is correctly positioned. This may indeed clip some highlights and perhaps shadows, but will give the best representation of the subject matter with in the limits of an in camera jpeg.

More advanced users “shooting to the right” and using raw, will of course have more options and latitude, and can adjust the position of the tones to avoid clipping and maximise quality. However they will need to readjust the image during raw processing, to gain the maximum advantage. (I did not cover this in the original OP as it is not a “beginner” option.)

“Blinkies” are no more accurate at showing the degree of clipping, than the histogram itself, as both rely on the same data from the attached jpeg or screen capture, not the raw data. The main advantage of blinkies is their attention grabbing value. I would suggest that you get the most advantage if they are used in conjunction with the histogram.

I grant that some people seem to be Histogram phobic, and derive nothing from their use.
Thankfully that is not the case for the majority of photographers.
 
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Coming from you… not surprised. Brilliant, Terry! :cool:
 
That's a great explanation. When I did attempt to get along with a dSLR I wasn't really sure what I was looking for in the histogram but had heard so many times that it was important to check it.
 
Lots of good information there Terry, but I have to disagree on some fairly fundamental points. In your opening sentence you say histograms are hard to explain and understand. I don't believe they are. And then you claim "What they do not show is exposure" when they absolutely do - that is their main purpose and usefulness.

The histogram simply shows the distribution of tones recorded on the sensor, with bright tones on the right, dark tones on the left, and mid-grey (I call it elephant grey) in the middle. The height of the graph represents the image area occupied by those tones. 'Technically correct' exposure is when mid-grey tones in the subject sit in the middle of the graph and they can be moved left or right by increasing or decreasing exposure settings. (That does not mean every correctly exposed image will have a big lump in the middle, and it won't if the subject is predominantly bright, or dark, or a bit of both like a sunset with a dark foreground.)

The trick is being able to visually identify mid-grey tones in the subject and relate them to what's shown on the graph. That's what the exposure metering system is trying to achieve so hopefully the camera will get them somewhere close, but it's easy to move everything left or right with adjustment of either shutter speed, lens aperture or ISO. Common mid-grey references (in the absense of elephants) are grass, brickwork, some tarmac, etc. These subjects also often occupy quite large areas of the image and will shown as lumps or peaks, making them easier to identify. Skin tones are usually around half way between the middle and right-hand side and with some cameras if you zoom in on the LCD image, the histogram changes to show just that area, which is very handy.

Having said all that, I'm with Dave and tend to use blinkies (highlight over-exposure warning) rather than the histogram as an exposure guide. Basic ETTR (Expose-To-The-Right, of the histogram) technique, but that's another topic.
 
… what a waste of time histograms are in YOUR general use possibly.

Ok, to clarify then

I shoot Weddings & Portraits for a living - histograms are no use to me here

I teach Landscape Photography for fun & income - histograms are no use to me here

My main hobby, other than driving, is photography where I shoot a range of subjects - histograms are no use to me here


I honestly can't see why any beginner should spend any time bothering to learn what they are, any more than a learner driver needs to know how their car's camshaft works; its fine if you want to delve into it but in Terry's great examples above the histograms are only telling you what's there, not what or if you should do anything about it

Feel free to make your case for why they are so useful to you in whatever it is you shoot :)

Dave
 
Ok, to clarify then

I shoot Weddings & Portraits for a living - histograms are no use to me here

I teach Landscape Photography for fun & income - histograms are no use to me here

My main hobby, other than driving, is photography where I shoot a range of subjects - histograms are no use to me here


I honestly can't see why any beginner should spend any time bothering to learn what they are, any more than a learner driver needs to know how their car's camshaft works; its fine if you want to delve into it but in Terry's great examples above the histograms are only telling you what's there, not what or if you should do anything about it

Feel free to make your case for why they are so useful to you in whatever it is you shoot :)

Dave

I know where you're coming from Dave, and I think we both prefer the blinkies/ETTR method, but that only works if you shoot Raw and post-process. If the output is JPEGs straight from the camera, 'technically correct' exposure (as opposed to 'optimised' ETTR or whatever) is the only way to ensure an image that looks properly exposed on the PC or when printed, without any adjustment.
 
I'm with Dave and tend to use blinkies (highlight over-exposure warning) rather than the histogram as an exposure guide


I advocate ETTL! :) …specially with Nikon's great DR.

I use the histogram to make sure I am away from either walls and use
+/- EV to remove the blinks… but preserve the whites at all costs!
 
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I know where you're coming from Dave, and I think we both prefer the blinkies/ETTR method, but that only works if you shoot Raw and post-process. If the output is JPEGs straight from the camera, 'technically correct' exposure (as opposed to 'optimised' ETTR or whatever) is the only way to ensure an image that looks properly exposed on the PC or when printed, without any adjustment.

You are quite correct,
For Jpegs to look correctly exposed, mid tones need to sit in the middle of the histogram. Unfortunately this often leads to slight clipping of the highlights.
"best" exposure is something different, and is only really applicable when shooting raw. as "Best" exposure is about capturing the maximum light with out clipping (exposing to the right). It entails a certain amount of post processing to return the captured tones to their correct positions. But having done so will give the best possible image in terms of tonal range and noise with little if any clipping.
If you have tones in the spectral region they will be pure white anyway.

This thread was aimed at beginners who almost to a fault shoot Jpegs. so I purposely did not cover post processing or exposing to the right.
 
I advocate ETTL! :) …specially with Nikon's great DR.

I use the histogram to make sure I am away from either walls and use
+/- EV to remove the blinks… but preserve the whites at all costs!

Don't we all, It only takes a glance.
 
Don't we all, It only takes a glance.


Apparently not… if you look at some posts and their renditions.
That makes your thread ever more pertinent. (y)
 
Thanks Terry,

It's what makes the forum great the time people take to write these posts, passing on their knowledge - I appreciate the contributors who are prepared to do this. :)
 
I advocate ETTL! ... use the histogram to make sure I am away from either walls and use
+/- EV to remove the blinks… but preserve the whites at all costs!

I can never understand why everyone doesn't do this and people so often rabbit on about ettr. Basic stuff!
 
Histograms aren't of any use to me either. Maybe I want to clip, maybe I don't. Maybe I want over-exposure, maybe I want under...

However - it was useful to learn what they were so that I could make a decision that they were of no use to me. So in that regard, I think this is a useful resource, even if it's only useful to help you make a decision as to whether it's something that you'll find useful. Which - for me - as an amateur that prints fine art for his own pleasure - is of no use at all.

tl;dr Histograms aren't right or wrong - they just are. But understanding what they are is useful if you didn't know.
 
Maybe I want to clip, maybe I don't. Maybe I want over-exposure, maybe I want under...


… and there is no better tool to tell you by how much
because your over / underexposure may go wrong if
not under some kind of control. :cool:
 
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… dnd there is no better tool to tell you by how much
because your over / underexposure may go wrong if
not under some kind of control. :cool:

Again I disagree

Yes histograms will point out that something is potentially wrong, but only blinkies will tell you where and then its a case of does it matter or not. A histogram telling you part of your image is blown is useless as it can't also show you which bit - i.e. in my world a white dress and a bright sky

Histograms are about as useful as your wife in the car telling you you've gone the wrong way but not knowing which way you wanted to go, or even which way is better - so like having a wife to give directions they are pointless & annoying in most cases :D

Dave
 
A histogram telling you part of your image is blown is useless as it can't also show you which bit.

This. The wife quote is also fab. I'm going to pinch that one.
 
Again I disagree

Yes histograms will point out that something is potentially wrong, but only blinkies will tell you where and then its a case of does it matter or not. A histogram telling you part of your image is blown is useless as it can't also show you which bit - i.e. in my world a white dress and a bright sky

Histograms are about as useful as your wife in the car telling you you've gone the wrong way but not knowing which way you wanted to go, or even which way is better - so like having a wife to give directions they are pointless & annoying in most cases :D

Dave

Actually a histogram does contain all the necessary information to come to these decisions. That is why knowing how to interpret them is useful.
Blinkies are also a blunt tool, as they appear quite a while before clipping occurs in a raw file, as they too are based on the inbuilt Jpeg.
But that does not mean that they are not a useful tool.

However in the heat of battle we may not get the best out of either the Histogram nor the Blinkies.

White dresses, Black suits and bright skys, are all indicated in the respective parts of the histogram. blinkies just bring problems to your attention.
 
Again I disagree

Yes histograms will point out that something is potentially wrong, but only blinkies will tell you where and then its a case of does it matter or not. A histogram telling you part of your image is blown is useless as it can't also show you which bit - i.e. in my world a white dress and a bright sky

Histograms are about as useful as your wife in the car telling you you've gone the wrong way but not knowing which way you wanted to go, or even which way is better - so like having a wife to give directions they are pointless & annoying in most cases :D

Dave


You're single right Dave?
 
While my default method for setting exposure is the ETTR/blinkies way, I often refer to the shadow end of the histogram.

ETTR is basically to push as much light into the image as possible without clipping, and let the mid-tones and shadows look after themselves. Which usually works well, but I check the histogram to make sure the shadows are not still rammed up against the left-hand wall.

If they are, there's not much more you can do with camera settings, so the only way around it is to rebalance the range of tones and put some extra light into the shadows, ie use flash. I do that a lot. In principle, it's the same idea - reducing dynamic range - as using a graduated filter to control a bright sky.
 
There is useful information in a histogram about the position of the highlights and shadows. I can see how that is useful. But I can't see any use of the bit in between. If I have a larger area of some mid tone than some other mid tone so what? I can already see that in the picture or viewfinder.
 
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There is useful information in a histogram about the position of the highlights and shadows. I can see how that is useful. But I can't see any use of the bit in between. If I have a larger area of some mid tone than some other mid tone so what? I can already see that in the picture or viewfinder.

The "So what" Is what much of what we are discussing is about.
If you are looking at a histogram so as to decide which way to adjust your exposure the "ends" are the main bits you are interested in.
However a histogram is also a useful tool during post processing. They will change as you make adjustment. Also causing blinkies and change shape, as you recover detail, change contrast , and brightness etc. You can learn a lot from a hisogram or ignore it entirely, and like any other "knowledge " it is up to you how far you need or want to push this. But at the very least it can show you in graphical form, how the various tones are related to changes you make.
How much this interests you is an entirely different matter.

A large area of mid tone not showing as a midtone in the histogram, but as a dark or light tone, is clearly somthing that would need addressing.
 
Surely when post-processing, apart from referencing the extremes on the histogram, for what all the tones in between are doing you reference the image itself?
 
I think histograms are a great guide to getting it right in camera, based on the scene being surveyed and what you as the image maker want. I often find, whilst shooting fully manual mode at my camera club, I can get the exposure I want in one shot. Others may make 4 or 5 attempts with step adjustments to get what they want.

Personally i find blinkies to distracting when composing but we all have our own methods and what suits you as the image maker is the best method.
 
Surely when post-processing, apart from referencing the extremes on the histogram, for what all the tones in between are doing you reference the image itself?

Yes, obviously reference the image but that can be very misleading, just as the LCD on the camera can be. The problem is, what's on screen bears no relation to your working environment/surroundings, unlike a print would or does, so you have nothing firm to reference visually.

So I use anything I can, including the historgam, but also the red highlight blinkies in Lightroom, and the blue shadow warning. I also reference the background in the Lightroom working area which is exactly 50% RBG neutral grey* middle of the histogram. I use that quite a lot as a reference guide for both exposure/brightness and colour balance.

*Edit: standard default setting
 
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Surely when post-processing, apart from referencing the extremes on the histogram, for what all the tones in between are doing you reference the image itself?

@HoppyUK has answered your question very well for this thread, and while I do not think delving too deeply into PP is the aim of this thread, I would add that I usually process my raws within photoshop, and make further adjustments in that program on to my resulting tiffs. In so doing I avail my self of every aid that that program can offer as needed. Including the histogram.
In fact the histogram is the last thing that I check before saving the file.
 
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Histogram Addendum
Now that this thread has reached maturity, there are a couple of points that were raised that need clarification.
( I will also add this post back into the OP….. )

@HoppyUK said you claim "What they do not show is exposure" when they absolutely do - that is their main purpose and usefulness.”

Answer:
You can derive no Exposure information or settings from examining a histogram,
Two entirely different exposures and illumination, can show the exact same histogram.
A histogram does not take into account your intent, it only shows the tonal values that you have or are about to capture.
What it does do… is to give you a guide as to where those tone fall, and the direction that you would need to adjust exposure or exposure compensation to centralise those tones or avoid clipping.
It gives you no information about the magnitude or value of those adjustments.
Adjustments can only be made by trial and error and observation of the changed histogram.

The information a Histogram gives in this way, is indeed useful to correcting exposures



@DGphototraining said

Nicely proving what a waste of time histograms are in general use”
and
“They may tell you what is clipped, but only you know if it matters or not, which is why "blinkies" are so much more useful if you follow the ETTR method”


Answer:
Centralising a histogram is especially useful to a beginner shooting Jpegs, who needs to get the image tones pegged, so as that the mid tone is correctly positioned. This may indeed clip some highlights and perhaps shadows, but will give the best representation of the subject matter with in the limits of an in camera jpeg.

More advanced users “shooting to the right” and using raw, will of course have more options and latitude, and can adjust the position of the tones to avoid clipping and maximise quality. However they will need to readjust the image during raw processing, to gain the maximum advantage. (I did not cover this in the original OP as it is not a “beginner” option.)

“Blinkies” are no more accurate at showing the degree of clipping, than the histogram itself, as both rely on the same data from the attached jpeg or screen capture, not the raw data. The main advantage of blinkies is their attention grabbing value. I would suggest that you get the most advantage if they are used in conjunction with the histogram.

I grant that some people seem to be Histogram phobic, and derive nothing from their use.
Thankfully that is not the case for the majority of photographers.
 
Histogram Addendum
Now that this thread has reached maturity, there are a couple of points that were raised that need clarification.
( I will also add this post back into the OP….. )

@HoppyUK said you claim "What they do not show is exposure" when they absolutely do - that is their main purpose and usefulness.”

Answer:
You can derive no Exposure information or settings from examining a histogram,
Two entirely different exposures and illumination, can show the exact same histogram.
A histogram does not take into account your intent, it only shows the tonal values that you have or are about to capture.
What it does do… is to give you a guide as to where those tone fall, and the direction that you would need to adjust exposure or exposure compensation to centralise those tones or avoid clipping.
It gives you no information about the magnitude or value of those adjustments.
Adjustments can only be made by trial and error and observation of the changed histogram.

The information a Histogram gives in this way, is indeed useful to correcting exposures



@DGphototraining said

Nicely proving what a waste of time histograms are in general use”
and
“They may tell you what is clipped, but only you know if it matters or not, which is why "blinkies" are so much more useful if you follow the ETTR method”


Answer:
Centralising a histogram is especially useful to a beginner shooting Jpegs, who needs to get the image tones pegged, so as that the mid tone is correctly positioned. This may indeed clip some highlights and perhaps shadows, but will give the best representation of the subject matter with in the limits of an in camera jpeg.

More advanced users “shooting to the right” and using raw, will of course have more options and latitude, and can adjust the position of the tones to avoid clipping and maximise quality. However they will need to readjust the image during raw processing, to gain the maximum advantage. (I did not cover this in the original OP as it is not a “beginner” option.)

“Blinkies” are no more accurate at showing the degree of clipping, than the histogram itself, as both rely on the same data from the attached jpeg or screen capture, not the raw data. The main advantage of blinkies is their attention grabbing value. I would suggest that you get the most advantage if they are used in conjunction with the histogram.

I grant that some people seem to be Histogram phobic, and derive nothing from their use.
Thankfully that is not the case for the majority of photographers.

You're being picky to the point of unhelpful. Fortunately, you added the line in red.

The big advantage of blinkies is they show you exactly where in the image the they refer to.
 
None of this is a problem :runaway:

if you use film :D

:film:
 
You're being picky to the point of unhelpful. Fortunately, you added the line in red.

The big advantage of blinkies is they show you exactly where in the image the they refer to.

Though I somtimes use blinkies I simply use them as a warning, as it is always obvious where they will be. And where ever they are,
my next action is the same,. Look at the histogram and shift the exposure.

For a beginner using jpegs, blinkies are of doubtful value, as shifting the exposure is likely to spoil the over all result
 
I would have thought histogram would have been as much use to beginners regarding making sure you don’t block up the shadows and knowing how much room you can move to the right to avoid that. With modern sensors you can recover a certain amount of highlight detail but you won’t unblock the shadows.
 
None of this is a problem :runaway:if you use film

Think of what could have been done and
the money saved if we had the histogram.

…just think of the Polaroids… :jawdrop:
 
None of this is a problem :runaway:

if you use film :D

:film:


But with film you can use incident light meters to peg your tonal values.
They do avery good but unnecessary job with digital too.
 
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I would just like to say a big thank you for this post, its really helped me to start ot understand the histogram a little more, much as I thought I was starting to get it before, there are some pretty complicated minefields in photography.
 
When I first started taking digital photos about 4 years ago I thought that I would have to learn all about histograms. But I very soon started to only shoot RAW, never JPEGs, and have never felt a need to learn about histograms. I think my Flickr pages illustrate that not all photographers need to focus on histograms - It's enough to concentrate on capturing the moment in sharp focus, aperture for depth-of-field, shutter speed and ISO (I shoot Manual-mode) with wildlife subjects!

It doesn't seem to matter that many of my images show the histogram 'mountains' to the left. Otherwise central but rarely to the righthand side. I only notice the histogram shape at all when post-processing and I always Auto process the histogram palette (in Capture One).
 
Keep your arbitrary on this, it is not totally infallible.

....Yes, I know and sometimes (not often at all) after clicking Auto and seeing a horror story I then revert to original without altering it rather than play with the 3 sliders and getting it wrong.

It's normally the last palette I adjust anyway.

Btw, thanks for the advice Kodiak - Always appreciated!
 
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