Monday, August 9, 2010

Enhancing aquarium photos

Pictures taken in aquariums can turn out less than stunning. Especially for creatures in large tanks, the photos may lack the crispness that brings anGrouper - Georgia Aquarium image to life. Let me show you what I am talking about.

Here is an otherwise nice photo of a grouper. It looks hazy and, well, bland, because of the turbidity of the water.

The photo has nothing that is black, and nothing that is white. The range of brightness values can be best illustrated by looking at a histogram of the photo. A histogram plots the distribution of tones from black to white along the horizontal axis, with the number of occurrences for each value on the vertical axis. Most image editingimage programs provide such plots, many cameras even do so. Here is the histogram for this image as shown in Windows Live Photo Gallery. I like that tool because it is simple to use and provides a number of very useful tools for enhancing pictures.

As you can see there are no pixels near the black (left) end of the scale and none on the right end. Photos with pixels covering the entire range from black to white are visually more satisfying, they “sparkle”.

One of the first, and easiest things we can do is to stretch out the pixel tone values. Live Photo Gallery makes that quite easy. Note the little markers on each end of the histogram. These are actually slider controls that can be used to set the black (left) and white ends of the spread of values. Not only can this adjustment be made by just dragging with the mouse, the results of the operation are displayed instantly and continuously. Here is the view of the program with the range adjusted as it appears best to me.


Notice that I dragged the black end slider (see red arrows) up so it is just at the left end of the pixel values. I did not bring the right, white, control all the way to the highest pixel. It just looked better to me this way. Also note that I set the Color temperature to the the warm end of the range. Live Photo Gallery provides, as do other similar programs, additional controls. These too operate “live” so you can see the results as you move the sliders. Now, doesn’t this improve the photo nicely?

There is one other disturbing little flaw. Note the white “running light” on the fish. This must be a reflection in the glass, so I want to get rid of it.

Image editors, especially the pricey, full-featured ones, offer great tools for imageretouching and modifying pictures. Live Photo Gallery (here in the 2011 beta edition) has a very easy to use retouch tool.

Click on Retouch, drag a rectangle around the flaw, and Photo Gallery analyses the area around the flaw, finds an area that would be a good match and copies it in.  It gets it right on the first try most of the time. If it is not right, repeating the operation causes it to find a better fitting patch. Really easy.

So what were the steps I took to enhance this picture?

  • I “stretched” the pixels using the histogram tool,
  • took the edge of the excessively “cold”, blue, cast with the Color temperature control,
  • and retouched a reflection flaw.

The editing tools in your picture management of image editing program allow you to enhance your photos so they look like you remember seeing the scene, even if in actuality it was not as impressive.

Click Aquarium Slide Show to see a collection of some of my, slightly enhanced, photos that I took at the Georgia Aquarium.

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1 comment:

  1. Brilliant post Ludwig! Your teaching me new things!I didn't realise you could do this with the histogram. Note. You can post to the Clubhouse using this blog, did you know that?