My lessons from this exercise:
1) In an ideal world….There wouldn’t be a need for a gamma correction if all components of an imaging system (cameras, printers, monitors, computers, scanners etc) had linear characteristics.
2) Why is it important? I think that a gamma correction is important for displaying an image accurately. Most displays, films, and many digital cameras have nonlinear (what is sometimes called ‘signal-to-light-intensity’) characteristics. So, a gamma correction is used to adjust an image to make it ready for reproduction or display. It is about choosing which part of the original image’s dynamic range will be reproduced.
3) So, how does it work? It’s interesting to note
that gamma corrections apply to each part of the image transfer process. The camera receives an image and applies a correction to make it ready for storage and transmission. A computer monitor may apply its own gamma correction when the image is transferred across to the computer system. So, having some standard gamma values means that different components of the system ‘talk to each other’ easier and that the image is reproduced accurately.
that gamma corrections apply to each part of the image transfer process. The camera receives an image and applies a correction to make it ready for storage and transmission. A computer monitor may apply its own gamma correction when the image is transferred across to the computer system. So, having some standard gamma values means that different components of the system ‘talk to each other’ easier and that the image is reproduced accurately.
4) A logical conclusion from the above is that in a well-calibrated computer system (which includes hardware and software) each component would have specified gamma values for its input and output. This would mean that where an appropriate gamma correction is applied for the system, the output would accurately reproduce the image input.
5) Now, to some number crunching! I looked through the available internet sources and my text books and found a variety of gamma values that usually apply. Apparently, negative film typically has a gamma less than 1 and slide film has a gamma higher than 1. And in most computer systems, an input gamma for images is around 0.45 and an output gamma is 2.2. Macintosh computers use (though I think it refers mostly to the old system so maybe it’s better to say ‘used’) 0.55 and 1.8 respectively. It’s interesting that apparently PCs have no standard built-in gamma correction. I also know that Adobe Photoshop allows the gamma correction to be changed (Preferences - Monitor Setup).
