The histogram allows you to obtain information about the exposure of your photo in order to better analyze the distribution of tones.
Its visual graph represents the brightness of the pixels in a photo.
It is a very useful tool that you can use when taking a picture, but also to process your images.
It is present on your camera along with the photos you have taken and in image processing software.
How to read the histogram of a photo
In order to be able to judge whether the exposure of your photo is correct or not, you need to be able to analyze this graph.
The horizontal axis on the x-axis represents the different tones from the darkest to the lightest through the middle tones in the center.
The vertical axis on the ordinate represents the number of pixels of each tone.
Clipping occurs when tone values exceed the right, left, or top of the graph.
With this information, you will be able to tell if your photo is correct, underexposed, overexposed, or lacks contrast.
Histogram of an underexposed photo
This histogram clearly shows that the photo is underexposed.
Shifted to the left in dark tones, the pixels overflow the frame.
The shadows are therefore blocked.
The solution would be to open the diaphragm, or reduce your speed or increase the sensitivity to let more light in.
Histogram of an over-exposed photo
This one has values that go beyond the right side of the frame.
The photo is overexposed, resulting in burnt out highlights, without details.
To remedy this, you must close the diaphragm or increase your speed, or lower the sensitivity of your camera.
Histogram of a low contrast photo
This graph shows values centered in the midtones.
Information is missing in the left and right shadows in the highlights.
The photo is lacking in contrast.
It is said to be soft.
Histogram of a correctly exposed photo
Visually, you can see that the values are well distributed, going from the left (dark tones), the center (medium tones) and the right (light tones), without them overflowing the frame.
We can deduce that the photo is well exposed.
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The standard histogram does not exist.
It is important to know that each photo has its own histogram, and that it cannot always be represented with uniformly distributed values.
Some images will require a deliberate underexposure or overexposure for creative rendering, for example when you want to make Low Key or High Key photos.
If you photograph a subject lit by candles in the dark, the distribution of values in the histogram will not be homogeneous, and this is normal.
The photo above clearly shows a histogram plotted to the left, indicating underexposure, but the exposure is artistically good.
So consider the nature of the subject before changing your exposure.
If the same image had been exposed longer, the histogram would be more uniform, but the mood of the image would be more uniform.
this photo would not be as intimate.
The histogram is a very good indicator of contrast.
Some scenes may have certain pitfalls.
For example, a foggy landscape inherently reflects a low and soft contrast.
Its histogram is usually quite centered, showing no or few values in absolute black and pure white.
Do not try to modify the exposure to obtain a perfect histogram if the general atmosphere of the landscape to be rendered is already harmonious as such.
Conversely, a backlight will have its histogram upset by the contrast it creates.
The graph will display many values in the shadows as well as in the highlights, but not or
very little in the middle tones.
I advise you to be careful not to pierce the values too much in the light tones and block the parts
darkened image to avoid excessive contrast.
It is necessary to find a compromise because this type of subject must keep a certain contrast, it is nevertheless the
Do not focus on the histogram
Now you know how to recognize the different exposures that the histogram may display in different cases.
You should also be able to know how to correct the exposure when needed with this tool.
The screen of your camera doesn’t tell you everything, even if it’s of good quality, and relying on it to correct
finely the exhibition would be a false good idea.
Sometimes, when the outside brightness is important, reflections prevent the good reading of a photo.
In this case your best ally will be the histogram.
Don’t hesitate to do exposure bracketing if you can’t make an analysis of the histogram.
Also think about working in raw format which will help you to rectify the exposure more precisely to catch burnt out highlights or blocked blacks.
To conclude, I strongly encourage you to take a look at the histogram, it doesn’t cost anything and it sometimes allows you to avoid unpleasant surprises.
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