Exercise: Sensor Linear Capture

The aim of this exercise was to take any jpg image and to open it in Photoshop Elements. Convert it to 16 bits per channel and then to use the adjustments and curves too to replicate the example in the course book.

This curve should be close to what the image looked like as it was captured and before the camera’s processor got to work on it.

For this exercise I chose an image that I’d taken in raw and converted to jpg previously of the Red Arrows. I usually use Photoshop Elements 9 but I actually didn’t have the facility to alter the channel to 16 bits. I did opt to continue as I was but I didn’t feel that I actually gain the results that I should see so as I’ve been looking at moving to Photoshop CS5 or6, I used a trial version which gave me all the functionality that I needed.

After opening the image, I used the curves function and recreated it in line with the example. I didn’t expect it to be so dark, despite the information stating that it would be.

Original Image

Sensor linear capture 1

Curves adjusted Image

Sensor linear capture 1 with curves

The next step was to open both images with the histograms and to compare the two.

Original with histogram


Edited with histogram


Looking at the histogram for the non edited image, the tones are all quite high but grouped together in the middle zone. When looking at the histogram of the linear image, the tones are all over on the left hand side compared to the course notes of on the right hand side. After reading fellow students journals, it seems that this is not just a one off result for me.

The second part was to put both images side by side and to open the Curves dialog to make a curve to make the darker linear one look as close as possible to the original. In doing this, I would be replicating what the camera’s processor does.

histogram for pt 2

When playing with the curves, I found that I moved the curve too much to the left, that it was too bright and with this came increased noise. One problem that I had was that despite trying a number of adjustments, I couldn’t match the colours to be as pale as those in the original. The difference between the darker image and this is obviously a number of stops difference.

When I zoomed in to view the image at 100% this was where I started to see the noise, it wasn’t much and was more in the type that looks like a film grain as compared to something that distracted from the image, but it was definitely more obvious in the darker shadow areas. Where the shadow areas are lightened, the noise will be exaggerated.


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