Underwater Photoshop Lesson - Gaussian Blur

Underwater Photoshop Lesson - Gaussian Blur


Editing underwater photos in photoshop is very much a matter of taste. Some people may like the results of a change in photoshop, while another may not. In this series of lessons, I will simply share the tools that I've used to manipulate various underwater photographs.


Original Underwater Photo before photoshop


original underwater photo

Underwater Photo before post-processing, jpeg generated from RAW file.




This photo was taken by a friend of mine with a Canon Xti, Canon 60mm lens, F16, 1/160th. He was concerned the photo wasn't sharp and didn't "pop".


After looking at the photo at 100% magnification, I told him I though his focus was correct, and given the water clarity, subject and lens it was as sharp as the front of a sculpin could be. But perceived sharpness and "pop" is a different matter, so I took 2 minutes and tried to edit the photo.


First, I used Adobe Camera Raw (ACR - same as using Lightroom). The color temperature of the photo was 6600K, a little warm, and the red color channel was overexposed in the histogram. so I brought the temperature down to 4800K using the white-balance slider, which reduced the saturation of the reds and oranges, bringing in more blue. I also adjusted the blacks, contrast and levels slightly. Last, I cropped the photo to give more of a fill-the-frame composition.


Then, I used Adobe Photoshop to touch up the photo. I used the healing tool and clone stamp tool to clean up some backscatter and to remove a small bright area to the right of the fish that was a small hot spot. Finally, to make the photo pop more and blur the background, I used the selection tool followed by the gaussian blur several times.


Three times in a row, I would select an area around the fish's head using the selection tool, feather it at 30-60 pixels, invert the selection, and apply a gaussian blur (under filters, blur) of 10-25 pixels. Doing this 3 times at different distances from the head of the fish allowed me to blur the background more, the further away I was from the head. This way there was less of a distinct line between the sharp area and the blurred area.


underwater photo after processing in photoshop

Underwater photo after processing. Some people saw this photo and asked, how did you change the depth of field? I had to smile, since you really can't change the depth of field, but you can try.


I should mention that while most people preferred the 2nd photo, some also preferred the color of the 1st photo, and maybe I should not have cooled down the color temp so much.


Achieving these results in-camera


This effect can also be achieved in your underwater photography by using a longer lens like a 100mm lens, and a smaller f-stop such as F10. You can try it with a 60mm lens, but you must use an even smaller f-stop like F6, and the results may not look as nice.



Further Reading

Macro lens section - 60mm vs 100mm

Guide to fish photography

Post-processing using Photoshop