A large number of photographers remain horribly confused by color management. However, it’s a fairly simple process that ensures our images maintain a consistent appearance when viewed in print or elsewhere. Very few photographers are aware that accurate exposure plays a key role in extracting the best possible color and making post production more efficient.
To obtain accurate color, we first need to set the White Balance correctly which can be done by photographing a neutral target to set a custom White Balance. This sets the base color temperature for the scene, so greys lose any color bias, while whites remain clean – without hints of magenta or blue, for example.
It doesn’t matter if the target image is upside-down or even blurred with camera shake, but it must be evenly illuminated and accurately exposed, otherwise the White Balance is likely to be incorrect. This is just one example of how exposure plays a part in color management.
Don’t Rely on the Camera’s Histogram for Judging Correct Exposure
There is a common misconception among photographers that you can rely on the camera’s histogram to judge the correct exposure, but this is a major error if you are shooting RAW files. The problem with camera histograms is that they display information based on the output of sRGB JPEGs, which offer nowhere near the potential range of tones found in Raw mode.
Digital sensors are linear devices, which means the biggest chunk of data is stored in the brightest part of the exposure, followed by a subsequent drop with each successive reduction in luminance. In practice, camera histograms start flashing highlight warnings long before necessary for RAW files with huge potential losses in dynamic range.
Depending on your camera, up to 50% of the potential dynamic range could be lost if you rely on the camera’s histogram, so if your camera is capable of reproducing a scene with 10 stops of dynamic range, 5 stops could be lost instantly with no means of recovery. That one small error is likely impacting every image you shoot; leading to flatter images with reduced shadow & highlight information unless you use a handheld meter to set an accurate exposure.
Use a Light Meter to Cut Down Post-Production Time
My personal choice is the Sekonic L-758D (also marketed as the L-758DR and L-758 Cine) that allows for exposure profiling based on the exact characteristics of the camera’s sensor and includes precise feedback about exposure latitude in any given situation. Using a handheld meter is actually the lazy man’s solution to cut down on post production work, while being no slower in practice than studying a histogram and estimating adjustments.
Photographers shooting JPEG need to be especially careful to set an accurate exposure and White Balance, since changes made in post production are highly destructive and likely to produce histogram combing, which represents missing data. The visual impact of this is will be rendered as abrupt tonal transitions that are particularly noticeable in areas of the sky, for example. See the below before and after histogram results of a JPEG file in Photoshop following a very minor tonal edit.
The simple fact is that if you set an accurate camera exposure and White Balance the rest of your color managed workflow should be remarkably straightforward; allowing you to exploit the full potential of your camera, while cutting down dramatically on time spent in post production. All of this and much more is discussed extensively in my new book Colour Management Pro.
– Ashley Karyl, guest blogger