What Is A Histogram And How Can It Help Us When We Shoot? Hi and welcome to Episode 114 of the Photography Explained podcast.
I’m your host Rick, and in each episode I will try to explain one photographic thing to you in plain English in less than 10 minutes (ish) without the irrelevant details. What I tell you is based on my lifetime of photographic experience. And not Google. No Google required but I did need my camera which was nice.
Before I go on I need your help. I need your questions to answer. More on this at the end but please have a think while you listen to this.
Here is the answery bit.
A histogram is a visual representation of the tones in a photo. A histogram is a graph which shows the distribution of the range of tones from black to white. Histograms can be found in most cameras, and also in image editing software such as Lightroom. A histogram will tell you if a photo has been under exposed or overexposed, or if the exposure is OK. Every histogram is different, and the data in a histogram can help with image capture and processing.
Right. That was my answer.
Let’s get into this one. And don’t worry, this is not as bad as it sounds.
What is a histogram?
A histogram is a visual or graphical representation of data using different bar heights for the different ranges of data.
Does that help?
No, not really. Oh well, I tried. Move on Rick.
What does a histogram show?
I am going to get straight into a practical explanation using my camera. On my Canon 6D there are two histograms. And what do they show?
I am going to let Canon explain. I am reading this from the Canon 6D manual ok? Well if Canon can’t get this right who can. And I have to tell you I find the way that Canon explain things in their manuals so helpful, so well written, so well explained. So I do not feel guilty quoting them.
“The brightness histogram shows the exposure level distribution and overall brightness. The RGB histogram is for checking the color saturation and gradation”.
Right, that is really helpful. Thank you Canon. I would just like to point out that you have spelt color wrong, it is colour. Not color. Just saying…..
And the manual is so helpful I am going to read the next bit from the manual as well.
“Brightness Display
The histogram is a graph showing the distribution of the image’s brightness level. The horizontal axis indicates the brightness level (darker on the left, brighter on the right), while the vertical axis indicates how many pixels exist for each brightness level. The more pixels there are toward the left, the darker the image. The more pixels there are towards the right, the brighter the image. If there are too many pixels on the left, the shadow detail will be lost. If there are too many pixels on the right, the highlight detail will be lost. The gradation in-between will be reproduced. By checking the image and its brightness histogram, you can see the exposure level inclination and the overall gradation”.
And there is more.
“RGB Display
The histogram is a graph showing the distribution of each primary colour’s brightness level in the image (RGB or red, green, and blue)”. I’ll stop there, if you want to know more check any Canon camera manual, freely available online.
The manual goes on, but basically it is the same as for the brightness, showing the values for the three primary colours instead.
But I will read this bit out. Again, I could not possibly put this better myself, so I won’t even try.
“The more pixels there are toward the left, the darker and less prominent the colour. The more pixels there are toward the right, the brighter and denser the colour”.
Right – that was the science bit. But what does this all mean?
First question, do I really need to know this?
Yes you do. It is important. How do I know this? Well, you will find a histogram in every camera as far as I am aware. But not on the iPhone. The default Photos app does not include a histogram, but there are apps that do.
Every camera?
Yes every camera. And there is a reason for that ok? If this wasn’t important camera manufacturers wouldn’t bother. And neither would Adobe, and other image processing software providers.
So this is important.
How does a histogram help me?
If you take a photo, and there is a high bit on the left hand edge, chances are you have underexposed the image. It is too dark, and you have lost details and data in the darks. You need to retake the photo, using either a wider aperture, slower shutter speed or higher ISO, letting more light reach the camera sensor.
Try this and look at the histogram. And everything should have moved to the right.
Same at the other end, but in reverse. Loads of peaks to the right hand side means an overexposed image.
That is it in a nutshell. Sure there is much more to this, but that is the headline news. The histogram will tell you if you need to change your camera settings to correctly expose an image.
The talky bit
You could spend the rest of your photography life not using the histogram, and if you are happy with that then fine. I did for years. But before you discount the histogram let me tell you a bit more.
Sometimes the histogram will tell you that an image is underexposed or overexposed, even though it looks fine to you. But what it is telling you is that there is data lost in the lights or the darks. And if you take a photo without all that data you cannot get it back.
And a tweak to your camera settings and you can get you that lost data and make a better photo.
And our starting point is getting the exposure correct in camera right? Well I say correct, the best exposure that we can.
So try this. After you have finished listening to me that is, not now.
Take a photo, look at the histogram, learn what is going on. And play with the exposure, underexpose, overexpose.
And look at this good stuff on your computer so you can see what is really going on. In Lightroom the histogram is top right on your screen. And even better Lightroom shows you where the clipped highlights or shadows on your screen.
Clipped means missed data, the stuff off to the left or right of the histogram that you have missed.
How useful is that? And by taking photos and deliberately underexposing and overexposing you have your own, practical examples to work with, study and learn from.
And let me tell you one last thing – just by doing what I have told you to do will start to improve your photos, as you will have a better understanding and awareness of exposure.
Sorry – I forgot - phones
Now I said that you will find a histogram in every camera. But not on the iPhone. The default Photos app does not include a histogram, but there are apps that do. And this is one of those things that sets cameras a level above phones, as wonderful as the picture taking capabilities of phones are these days.
It is data like this that we photographers use to consciously create better photos. So there is technical side to this, but also a level of thought by us photographers.
Agghhhh – one last, last thing. Camera manuals
Camera manuals are incredibly useful. I have a Pdf version of my Canon 6D on my PC, phone and iPad. And it is an incredibly useful reference point, and one that I refer to all the time when I am writing blog posts and podcast episodes.
What do I do?
Well, I use the brightness histogram one a lot, as it gives me incredibly useful information. I don’t use the colour one though. The colours I capture are what they are, and with the processing I do in Lightroom these are not going to change much.
But now I am going to look into this a bit more.
But for now the brightness histogram is very important to me, and is very useful information that we should all understand.
Related episodes
Lots and lots of them – just check out the episode page on the podcast website to find out what I have spoken about so far. I do not want to bore you by listing them here. I have said enough…..
Next episode
Photography Explained Podcast Episode 115 – A listener question! And I have some work to do on this one. This is the title. “Listener Question. My Gear Is Covered In Soot From The Great Dorset Steam Fair.” Yes, camera gear covered in soot. Thanks Terry.
Get your question answered.
This is what my podcast is all about, answering your photography questions. So please get in touch with your question, and not only will I answer your question, but I will give you a shout out on that episode, which is nice. Just head over to photographyexplainedpodcast.com/start.
OK - I’m done
Thanks for listening to my small but perfectly formed podcast. To find out more about my podcast and do stuff to help me check out the podcast website, which is photographyexplainedpodcast.com/.
This episode was brought to you by Yorkshire Tea and the last Biscoff cream biscuit in the house. Oh yes, sorry. And also by Canon through the Canon 6D Manual.
I’ve been Rick McEvoy, thanks again very much for listening to me and for giving 10 (ish) minutes of your valuable time, and I will see you on the next episode.
Cheers from me Rick