The Histogram - Part 1

Thread starter #1

JasonF

Senior Member
It's been a long time since anyone has posted up a tutorial of some sorts so here is one for ya.

I wanted to discuss the histogram within our cameras, how they work, and how to use them to edit our pictures. Hopefully some here can take something from this and its not seen as just a bunch of useless information. :)

First off, the histogram.
The histogram, for those who don't know, is that little graph we see when we look at the LCD on the back of our cameras. The histogram is EVERYTHING! It serves as a blueprint for the pictures we take and furthermore, learning how to read the histogram is a must for those who wish to grow in photography. The histogram, when knowing how to read it, will tell us how our exposure is after we take a picture.
Often times after we take a picture, we ignore the histogram and judge the image quality and exposure from looking at the sample on our LCD. More times than once, I've done this only to find when I get the image on my computer that it is underexposed. Now, had I checked the histogram in the field, I would have realized this and made the necessary adjustments resulting in a better shot.

To understand the histogram, I believe you have to break it down into sections. For this tutorial, I pulled some sample histograms from various resourses and although they may vary in appearance, they all tell the same story from an exposure standpoint.
A perfect histogram will look like a mountain range within the graph...something like this:



Above you can see that the dark areas, or exposure is spread out somewhat evenly acrossed the graph resulting in a good exposure.

It's important to note that the left side of the histogram above represents the shadows while the right side the highlights.
With that said, a histogram that is underexposed would look something like this, with the exposure leaning more torwards the left...a darker image:



And an image that is more overexposed would look something like this, with the exposure leaning more torwards the right...a much brighter image:



Blown highlights or shadows, which results in complete lost detail will have the dark areas, or exposure, reaching upwards and outside of the upper part of the graph.

You can also use the histogram to judge the images contrast.
A low contrast image would look like this with everything scrunched up towards the middle:



And a high contrast images histogram should look like this one:



...notice the good exposure here too!

Finally, most histograms will have lines running through them like so (I marked them with the red dots):



As you can see, the histogram is made up of 4 separate "boxes" each resulting in one stop of light. Soooo, this histogram seems to be a bit on the dark side with more room on the bright side (or right). To compensate, one would have to make the make the necessary adjustments to balance out the histogram more evenly (add +1 EV, drop the shutter speed down a stop, adjust your apeture or ISO).

And there you have it! Let the discussion begin and if I missed anything or was off the mark somewhere, please be sure to set me straight.

Next, in "Part 2" I'll run a image through photoshop step-by-step that was underexposed showing how to correct the mistakes I made in the field.
 
Last edited:

Hoss

Moderator
Jason, I can see this one and probably the ones to follow are going to the sticky at the top. I was thinking the other day, we haven't had any discussions like this in a very long time. Thanks for jumping in and getting things started.

Hoss
 
The histogram is one of the most alien and misunderstood aspects of digital photography. It is ironic it is the most useful tool a digital photographer has.
 

FERAL ONE

Shutter Mushin' Mod
excellent jason !!! i agree we need to have more "how to's " !!!
 
Thread starter #6

JasonF

Senior Member
The histogram is one of the most alien and misunderstood aspects of digital photography. It is ironic it is the most useful tool a digital photographer has.
Haha! Good point and very true!
 

marknga

GONetwork Member
Wonderful information.... thanks and I look forward to future lessons.
Exactly the kind of info I need.
 

tnhikr44

Senior Member
Very good tutorial, Jason. As normal, I find myself on the other side of 'normal'! I take most of my shots on the fly, meaning they are not set up, posed or planned. With that in mind, I almost never look at the picture on the screen, but mainly the histogram. I can tell by a quick glance of the histogram whether the shot is decent or 'fixable' (at that point focus and DOF are a moot point). That being said, I am looking forward to reading the next tutorial. I will certainly have some questions after that one.
 

quinn

Senior Member
Thanks Jason,it's awesome of you to take the time to help improve our photo's!
 
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