Exercise: Sensor Linear Capture.

Outline: Simulate a linear image quite simply by applying the opposite type of curve.

The image below is a jpeg from a recent trip on a nice sunny afternoon with plenty of lighting.

After loading up Elements i noticed that there was no option to convert the image from or to 16 bits. I think that it was already set at 16 bits as the link to alter it to 8 bits was unavailable...

So heading into the next task, I then noticed that by going into 'Image' there was no 'adjustments' option and no visible 'curves' option but after a bit of searching I found the option to adjust colour curves.

So using this option, I screen printed the image as it starts, showing the histogram with the points stretched over the whole graph.

I then altered the curve to one similar to that shown in the diagram...

This screen shot shows the before and after image with the curve I have created. I then saved the linear image and took a screen shot of the new histogram.

As noted in the exercise, the tonal values have now squashed over to the right compared to the original image.

I then altered this darker, linear image and amended the curve to that of the gamma correction curve in the example.

We now have an image of the two pictures, the dark linear one and the lightened one.  The shadows have been lightened, as have the highlights.

Here is the final, re lightened image with the histogram showing the tonal values leveled out again. This image still differs from the original with a smaller difference between the highlight and shadowed areas than in the original. The tonal values in the histogram are a lot lower and flatter than in the original as well. 

Conclusion: The ability to alter the curves has a dramatic effect on the image and the exercise has given a good insight into what the camera's processor does to the image once it has been captured.