I was introduced to the histogram, by the assistant in Jessops, during the whistle-stop tour of my first digital camera - a D40. He said it was very important, but too difficult to explain properly in 5 minutes. His instruction was to "look at it for every picture and it would become obvious" - I did and it did.
To become familiar with the histogram I simply went around pointing my camera at different things taking snap-shots and reviewing the graph. Initially I assumed that a good graph should be a normal distribution, but very quickly realised this was unachievable. Understanding the dynamic range of my digital camera highlighted the real differences between film and digital; at the same time as introducing the brand new world of image manipulation and the amalgamation of multiple photographs.
The best description I've read is: the histogram is simply representative of the style of image or subject matter; as such there is no such thing as a perfect histogram - Archna Gupta.
I find the histogram an invaluable tool and refer to it all the time. In bright sunlight or during the night, it is much easier to read a graph than it is to 'see' a photograph on the screen.
General guide for dynamic range:
Low contrast situation - where shadows are limited or none-existent
Ø Overcast sky with sky excluded ~ 3 EV
Ø Overcast sky and shade ~ 5-7 EV
Medium contrast situation - if your subject is side lit with a reflector bouncing light back into the scene
Ø Sun overhead at midday, with some shade ~ 7-9 EV
Ø Sunny day, side lit subject with some shade ~ 7-9 EV
High contrast situation - point your camera directly at a light source
Ø 100 watt bulb in small interior ~ 11-12 EV
Ø Night scene with street lights ~ 12-13 EV
Ø Interior with bright window light ~ 14-15 EV
Ø Bright sun back lit subjects ~ 15-17 EV
From an article by Roger Passman - http://www.picturecorrect.com/tips/dynamic-range-and-contrast-in-photography
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| Grass - low contrast |
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| Bridge across Bermuda infeed - average contrast |
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| Histograms for the Bridge at -1ev, 0ev, +1ev |
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| Park bench - high contrast |
The only clipping that occurred (in camera, without moving the exposure) was the sky in the image above - approximately one third of the sky is burnt out. This is hardly surprising since I was shooting directly into the sun - even though it was hidden behind the tree.
POLARIZERS
On a different but related subject - as I was doing this exercise I decided to investigate what affect a polarizer had on the histogram.
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| Without polarizer |
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| With polarizer |
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