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Menu: Adjust -> Gamma...

This allows you to apply Gamma correction to an image.You can immediately see results on the image as well as the Tone Curve.


What is gamma correction?

If an image pixel has an intensity of 255, that would mean it will produce twice as much light as a pixel with an intensity of 127. This is true only if the display device (monitor) is photometrically linear. This is far for current display devices. The relationship between the voltage and brightness of the monitor was approximated by: Intensity = Voltage^gamma. Gamma correction changes the intensity values by the inverse of this function:I' = I^(1/gamma)

This means that if you don't use the gamma correction on your monitor (or display software), your images will look darker on the monitor than they really are. Most people don't have calibrated monitors at home - so they don't use any gamma correction.

You have to think about this when you are preparing images for the internet. Instead of telling thousands of people to correct the nonlinearity in their monitor, you can just adjust your image.

Note: The average gamma value of monitors is about 2.2 - but remember your images were generally taken by non-linear devices, like Digital cameras or scanners. In most cases values around 1.4 looks best on most monitors.

If you look at the Tone Curve graph next to the Gamma slider you will see how you are adjusting the nonlinearity of the image.

Whatever is your reason to change gamma it basically makes the low-midtones look brighter, so you will see more details in shadows.




Tip: If you want full control over the curves and their characteristic, we would recommend you to use the "Smart Curve" plugin distributed with PhotoBrush. It's a very nice freeware PhotoShop compatible plugin made by Alois Zingl. You can find and install this plugin via menu Filters >> Plug-In Manager. The Plugin is located right in Photobrush/PSPlugins folder. Don't forget to contact the author and let him know how nice this plugin is! ;)