3.0     Non-Linear Processing

Non-linear processing for me takes us from our unstretched linear image up to the point where we export it as a JPEG for publishing. 

2.1     Stretch Image

The first step in the process is to stretch the image, this is basically a permanent version of the 'STF Auto Stretch'. First open the process, 'Process Menu > All Processes > Histogram Transformation' and follow the following steps.

• Click the Reset button, in the bottom right of the histogram transformation window.
• In the drop-down menu select your target image.
• Open the 'Real-Time Preview'.
• In the lower graph window, drag the middle slider to the left as shown in the image below:

• Apply this stretch to the target image in the usual way.
• Click the reset button and repeat the above process noting the following:
  • The ultimate goal of this is to have the Histogram in the top graphical window located over the second vertical line in the graph with a reasonable spread rather than just a flat slope.
  • Dragging the middle slider to the left will stretch the image to the right.
  • Dragging the left slider to the right will stretch the image to the left. Be careful not to get too close to the base of the curve using the left slider.
  • Once your curve is located around the desired position, you can use a combination of the left then middle slider will help spread out your curve to improve contrast.
• The image below shows the stage of the process where I would start using the left and middle slider combination to spread out the curve.

• If you find that the colour channels are misaligned you can select individual colour channels instead of the default 'RGB/K' and realign the channels using the same stretching method above.
• The image below would be what I consider the end result of my stretching process.

Once you are happy with this image you are ready to move onto the next stage.

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