How to Use a Histogram
how to use a histogram
how to use a histogram
Knowing how to use a histogram can feel like the kind of thing that makes you want to turn off the camera straight away when starting out.
Graphs? I mean graphs on the back of a camera?! Like I just want to take a photo – why do I need a maths degree now?
You don’t, you really don’t. When you know how to use a histogram you’ll see they are packed with information, and when used correctly, can change your photo;
..in to this!
What Will I Learn in this Guide?
- What is a histogram
- The benefits of using a histogram
- What is clipping?
- What does a good and bad exposure look like on a histogram?
What is a Histogram?
Histograms can appear on the back of your camera or even when editing – we’d advise you to have them visible whenever you can.
They are a representation of tones and brightness in the photo you are/have taken – as some cameras can give you a live reacting histogram (amazing!)
The chart denotes how many tones there are in a photo between true black (the left of the graph) and true white (to the right of the graph). The peaks in the chart show you the volume of a pixel in these tones.
All the tones in a histogram are charted from 255 (true black) down to 0 (true white). Though for beginner photography this numbering isn’t vastly important. Just as long as you know how to use a histogram to your favour.
Benefits of Using a Histogram
Photographers use histograms to chart their exposure. Knowing what the graph represents we can understand how bright our photograph is looking and how many dark and colourful areas there are.
You may think this is obvious, as you can see it, based on the photo on the camera screen – but 3-inch screens lie – or at least they aren’t showing you everything, and how can it at 3 inches? Don’t fully trust your LCD screen. Instead, trust your histogram.
The last thing you want is to be relying on your camera’s small screen preview for all the answers. It’s really hard to appreciate and gauge the detail of your photo at 3 inches, so instead, use the histogram to create your best possible exposure.
When you see peaks on your histogram like this (picture below) then this says there is a lot of pixels of one tone in our photo. Depending where along the horizontal these peaks appear tells you how to bring or dark these tones will be. Knowing this you can watch out for really bright areas that are over/underexposed.
As we said earlier, some cameras have a live reaction histogram to use while you’re shooting. Using this will tell you instantly whether your photo is evenly exposed or if it’s clipping. Try adjusting your aperture, ISO or shutter speed to change the exposure, and therefore the histogram. Either that or change the composition – even zooming in or out of your scene will change the exposure.
What is ‘Clipping’?
Yes, we snuck it in during the previous section – did you see? Clipping is like an alarm we need to look out for on a histogram.
When those peaks that we’ve mentioned hit the extreme left or right of our graph then that’s when our photo starts to ‘clip’.
What we mean by that is the exposure has hit or ‘clipped’ the limits of the range of colours available. Depending on which end of the graph the peak is at, either this means your shot is over or underexposed in some parts.
Clipping tends to occur when your sky is so bright it just looks like a white wall of nothing. You can zoom in to the photo but you won’t see any cloud detail. Conversely, if you’re shooting at night and the histogram is peaking on the left side then it means your shot is so dark in parts that it’ll just be a block of black.
Most of the time, unless it’s for a stylistic choice, you want to avoid clipping. Clipping removes flexibility when it comes to editing and also reduces the amount of detail in the final picture.
To avoid clipping make sure that your histogram never touches the extreme left or right edge of your chart. Make sure there is a little gap from the edge. In fact, some cameras have an exposure alert display while you’re shooting.
Little Zebra lines appear across areas that are close to clipping in the highlights (white areas). You can set this Zebra marking to appear at different points – 75%, 80% or 90%. Check your camera manual to see if you’ve got this function.
What does a Good and Bad Histogram look like?
Let’s just recap on the type of histogram that we are wanting to result in with our photos. You’ll never get two histograms looking the exact same, so don’t pressure yourself to always get them looking the same. Lighting conditions vary for everyone but just as long as you’re in the correct ballpark, you’ll be fine.
Remember that a ‘bad’ exposure (unless it’s for stylistic purposes) means that the histogram will be touching the far left or right of your graph. The last thing you want is peaks on each edge and a gully in the middle. This means your image is high contrast because only the extreme tones appear and not much else in the middle.
Ideally, you want the inverse of that. Aim to construct a hill once you know how to use a histogram. A hill that starts just off the edges of the graph and rises towards the middle. Remember though, this may not always be possible, and this ‘hill’ may look more like a rocky mountain range – which is fine too.
This ‘hill’ or ‘mountain range’ histogram means you’ll have some tones stand out more than others. Providing there aren’t too many individual gullies and peaks then you should have a decent amount of colour tone throughout your shot.
Have we managed to convince you of the power and usefulness of a histogram? Do you feel more confident in knowing how to use a histogram? Will it encourage you to use it while shooting from now on? We’d love to know.
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