Your Camera Histogram

What is your camera histogram? How do you use and apply it? Why even bother?

Simply, the histogram is a graphical representation of the information stored in the selected image file – from shadows on the left to hightlights on the right.

To access the histogram on a Nikon Camera, push the playback button, then press the down arrow of the selector dial:

 

 

This will now show some information about the selected image, including camera settings and the historgram which is the white graph to the right of the image:

 

 

The histogram shown here has the bulk of the data to the left of centre which means more shadows than highlights in the image. Note the left and right ends of the graph intersect the bottom line and don’t touch either side – this is good, exactly what you want.

You may have heard the term “clipping”? This is when the line of graph hits the left-most or right-most verticals above the base line which means that information is lost and parts of the image shadow will be just black, or some of the highlight areas will be white (burnt out). A good example is clouds on a sunny day, burnt out clouds are just pure white shapes instead of the moody contrasts so often attractive in clouds.

In reality you can get away with a small amount of “clipping” at times on the right particularly as this can be pulled back with in camera processing or with Photoshop or the like without losing any detail from the image.

I check my histogram for every image, and what I look for initially is:

1. No clipping.

2. Expose to the right.

 

We have discussed clipping, now exposing to the right means that the bulk of the image information is on the right side of center rather than the left as the histogram above. Why expose to the right? Darker exposures can introduce digital noise, which robs detail from the image.

A well exposed image will have a histogram something like this:

 

There is no “clipping” on either side which means we have not lost any digital information, there are no absolute blacks or whites. Most of the data is right of centre.

When processing this image, if I wanted more shadow for mood, I could reduce the brightness values in Photoshop and have nicely toned shadows with plenty of detail.

 

An under exposed image:

 

The bulk of information is to the left and the graph is “clipped” on the left hand side of the histogram. This means I have pure blacks in my image.

I likely would not process this image for a large quality print, but if I were to try and increase the brightness values, the shadows would have discoloration and details would be poor due to the noise from such an exposure.

An over exposure:

 

The “clipping” on the right means I have pure white in my image and alot of it with the bulk of the information stacked hard right.

Nothing can be done with this image – delete it, readjust your camera for another shot if you really like the subject: choose a smaller aperture if you want more depth of field ( the amount of the image that is in focus) or increasing your shutter speed – either will allow less light into the camera sensor, reducing the exposure levels, assuming you have already selected the lowest ISO for a quality landscape shot :

 

Don’t worry about how high the graph goes, concentrate on the left and right sides and having the bulk of the information to the right of center if possible.

I quickly (at times ruefully) learned to rely on my histogram after ruining more that a few images. One occasion cause me many hours of unnecessary editing and adjusting to satisfy the clients needs – if only I had checked the histogram and not relied on the camera live view!

I check now after each shot or burst of shots – a quick check showing no clipping and reasonable amount of data middle to right and I am happy.

I encourage every digital camera user to find and use the histogram on their model of camera. It is very easy to use and you can be confident of nicely exposed images.

I hope this is clear enough and helpful to some. See you ’round the ridges!

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