How to adjust underwater photos in Aperture

Blogged by Simon on February 02, 2010 5:23pm | Last updated by Simon on February 16, 2010 5:08pm | Pages: 1 2

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Step 2: Level Adjustments

Next, let’s change the overall exposure and colors. Note how the image still looks flat, lacking actual blacks and having little contrast. First, let’s bump up the contrast in Aperture by 15% to compensate for some of this.

A quick look at the histogram reveals there are still zero pixels in the bottom 5% and the top 2% range of the whole spectrum, so we compensate for this by limiting the range of the photo to the remaining 93%, then redistributing the color values for these pixels.

What this means is that you are now telling Aperture to set the new black to what used to be 5% grey. (This is done by sliding the little black marker underneath the histogram in the adjustments tab to the right. A similar thing happens to white at the bright end of the image by sliding the little white marker to the left).

In doing so, You are effectively discarding the color ranges for which your image did not have any pixels to begin with and are introducing real black and white tones back into your photo.

Let’s have a look at what happened. The contrast is improved, but the image also has more pop as it’s dynamic range has increased. This is already a step forward, however we still have the bright background which is distractive.

Step 3: Vignetting

The last step for us will be to introduce selective brightness to the image to draw more attention to our subject and away from the background. There are various so called vignette filters available to achieve this, here I am using the one out of the Nik Color Efex Pro plugin for Aperture.

Note that in this example the middle of the image isn’t the middle of your subject, so I am placing an Aperture control point towards the base of the fish head, telling Aperture to make this the brightest point. I then select an elliptical vignette shape and 50% opacity to prevent completely burning the edges. Next, I gradually adjust corner darkness until it feels right, to about -70% here.

The corner darkness is now most effective underneath the subject, because I placed the bright point slightly above and left of the middle. This makes our subject stand out a lot better against the background, compared to the previous version. Overall, we now have a lot more dark pixels, so this is a good time to do another round level adjustments if necessary, though I have skipped this step in this example.

Let’s have a look at the final result and compare it to the original version. Rotation and crop focus on our subject, we have better colors and much better subject to background separation. All in a few simple steps.

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