Today I’ll continue along on the underwater photography kick. Tony Wu is a professional photographer, who also keeps a blog which I enjoy reading.

The other day I was digging through archives and came across this article. Now, as a professional photographer, Tony takes massive amounts of expensive equipment underwater with him. In this post, he describes his experience going back to a simple point-and-shoot camera.

I found his description educational and encouraging—especially if you look at some of the pictures he manages to get on a relatively cheap camera.

You should particularly take note of his mention of a camera’s underwater mode. He also discusses the different approach to using a compact camera. How you have to view your subject differently.

I think it’s an interesting read both for amateurs already using point-and-shoot cameras as well as those who have moved on to SLRs.

We looked before at a super-easy, fast way of color balancing photos using Photoshop’s Auto Levels feature. But what if you need a little finer control? Today we’ll look at manually adjusting levels to fine-tune your pictures color balance. We’ll use this picture of a turtle.

Color balance

If you don’t know what I mean by color balance, it is simply the different amounts of different colors that are present in an image. Underwater photos taken without a flash or adjusted white balance tend to have a blue-centric color balance that usually needs correcting. Very few professional images that you see have not been tweaked in post-processing.

Usually, when we talk about colors, we talk about reds, greens, and blues. Every other color is a blend of these three (called the RGB color space). There are alternatives, of course.

One useful color space is CMYK, which stands for cyan, magenta, yellow, and key (black). This is useful because it acts like the complement to RGB. If you take a fully saturated picture (full red, green, and blue) and take out the blue, you get red and green. On a computer this is yellow. Similarly, the complement of red is magenta, and the complement of green is cyan. This becomes useful later.

Histogram

Open up the Levels in your image editor (in Photoshop, go to Image -> Adjustments – > Levels), you’ll see something that looks like the following:

This is called a histogram. Basically, it tells you the intensity of colors present in your photograph. You can see in our histogram there are a lot of darks present in the image. These are the shadows in the coral and the spots on the turtle.

You’ll notice that there is a drop-down box where you can select the channel. Either RGB, which is the combination of all colors, red, blue, or green. Switch to red and you’ll notice how there are few reds in the image, a characteristic of underwater photos.

If a histogram is concentrated towards the right, we say that it is a high key picture. If it goes all the way to the edge, it is “blown out”, or overexposed.

Conversely, a left-shifted histogram indicates a low key image. If it reaches the edge, then the picture is most likely underexposed.

This is a quick test to see if an image can be salvaged. If it is overexposed or underexposed, that means many of the pixels in the image are 100% white or 100% black. If that is the case, then no color balancing can really do anything for them. So unless the overexposure / underexposure is part of the look you are going for, you may not be able to do much with the image.

Fortunately, our image is not either, so we can tweak it to get colors a little stronger. We want to get rid of that blue haze.

Notice the little sliders at the bottom of the histogram. There are three, one indicates black, one white, and the other grey, or the midtone. These are adjustable, and redefine the range of colors in your photo. This is how we’ll get fine-tune control of our image’s color balance.

Levels

By adjusting the levels, we are adjusting the balance of colors in our image. Before we get started, I want to say:

• Do so with caution. Adjusting too much will be obvious. Think little edits.
• Play around. Explore the color space. No one can tell you exactly what will make the photo really pop.
• It’s artistic, there is no fixed solution. This is more art than science.

There are a few guidelines we can follow, though. In particular, you should know that what happens when you use Auto Levels in Photoshop. Look again at the following red histogram.

Notice how the balance is totally off? We’re going to fix this by moving the white slider. Because there are no pixels at that level, we can do so without losing any information in the image. By moving the white slider, we are telling Photoshop that anything to the right of the white slide should be considered pure white. Likewise, when moving the black slider, anything to the left of it is considered pure black.

When we move the white slider, it also moves the grey slider, which redefines what the midpoint color between white and black (depending on the channel) is. This redefines the entire color range.

Tightening up the edges of the histogram for each channel is basically what Auto Levels does. That’s why in the previous article, we say that it is a super-quick way to get good results. It moves the black and white sliders to the edge of the histogram, where the curve starts.

Go through each channel and adjust. Remember how I said the complement of red is magenta? Well, this is where it matters. When in the Red channel, black and white take on different meanings. For red, the white slider controls what is considered red (fully saturated red) while the black slider controls what is considered magenta (fully desaturated red).

Go overboard with the sliders (it’s easy to undo any changes). Doing so really illustrates what each slider in each channel does. By doing so, you get a feel for how the Levels tool works.

While adjusting, don’t neglect the grey midpoint slider. This changes the overall brightness of the image for each channel. For another description of Levels, read this article.

Here is our final image. Notice how the contrast is much better, and the image doesn’t appear nearly so washed out?

Here’s the corresponding histogram. There are some gaps, but it’s fairly balanced in the middle, which is generally what you are going for. There is still a bump towards the dark range. This is the turtle’s spots, which I want to have that strong dark color.

This tutorial assumes you have Photoshop (or Photoshop Elements). You don’t have to have these, though. Most modern image processing applications have a Levels feature. Look through the documentation for yours.

Now you know how to color balance your underwater photos. Next time we’ll look at how to post-process photos to really make your subjects pop.

On Tuesday we talked about underwater white balance, what it is and how you can do it. If you recall Step 2 of the process,

Point your camera at something you know is white and “take” a picture or press the appropriate button. The camera will record your settings.

This is potentially a problem. How many pure white objects are there in the ocean? Much less one that is a nice flat surface for setting white balance.

If you’re even semi-serious about getting good underwater pictures with your point-and-shoot, I recommend picking up a dive slate. Usually used for communicating via writing underwater, a dive slate makes for a nice flat, white surface perfect for manually setting white balance.

As a side bonus, slates are inexpensive. They often have a buckle or strap of some sort to attach to your BCD.

A dive slate is a useful gadget to have anyways, but becomes indispensable when you need to set white balance.

If you’re new to underwater photography, one thing you’ll quickly realize is that all of your pictures come out blue. If you want to know why, read my article on colors underwater.

Now that you know why, you want to know what you can do about it. Before you bought your camera, you looked at magazines and online photo galleries. None of those pictures have that blue haze.

To remedy this problem, you basically have two options: a strobe (flash) and adjusting white balance.

Underwater strobe / flash

Water (more specifically, stuff in water) absorbs frequencies of light the farther the light travels. Very quickly then, red light is absorbed, leaving everything a blue tint. One option is to then reintroduce white light, which contains all frequencies, into the environment.

If you’re taking a picture of a piece of coral at 10 meters, the light seen by your camera reflected off the coral has traveled over 10 meters, and will thus be dominantly blue, even if the camera is less than 1 meter away from the coral. By using a strobe, the camera will see not only the light that has traveled 10 meters, but the white light from the flash, which reintroduced the missing reds.

There are two downsides, however. First, the most common flash is the camera’s built-in flash. While fine for taking pictures of friends on land, underwater it tends to produce backscatter, where the light reflects off of particles in the water. The only way to prevent this with a built-in flash is to only use it up close (less than a meter).

Even if you manage to avoid backscatter, on-camera flash tends to be a bit harsh, giving you a fish equivalent of that “deer in headlights” look. An alternative is an external strobe which is attached by an adjustable arm. This lets you control the lighting more finely, both by arranging the direction (via the arm) and the strength to get a perfect exposure.

External strobes are expensive, but the vast majority of professional underwater photos you see used them. In the future we will look at them in more detail (as I learn more about them).

White balance

The other option available is by adjusting your camera’s white balance. You can adjust white balance two ways: on your camera and on your computer. However, you can only really adjust it on your computer if the picture was taken in an appropriate format (like RAW). This doesn’t apply for most point-and-shoot cameras. If you want to learn how to “cheat” white balancing on a computer, read my article on color balancing underwater pictures.

Most point-and-shoot cameras do support manual white balance, though. Check your camera’s documentation, but the process usually goes like this:

1. Set to manual white balance. Enter your camera’s system menus. You will probably find some settings for taking pictures indoors, on a sunny day, at night, etc. You are looking for anything that says “white balance” or maybe even “AWB” (automatic white balance). When you find it, you will want to change to manual.
2. Change the white balance. While still in the menu, you need to set the white balance. Point your camera at something you know is white and “take” a picture or press the appropriate button. The camera will record your settings.
3. Take your pictures. You can now take pictures as usual. Because light is absorbed differently at different depths, a white balance setting is only appropriate for around the depth it was set at. If you go deeper or shallower, you will need to repeat step 2.

Below I have side-by-side photos of the same coral with and without manual white balance.

The difference should be clear. Notice also how the after picture still isn’t quite perfect. While it’s much better, you may want to still touch up your pictures on the computer later.

What is white balance?

Cameras just record what they see, which is a bunch of colors (light). These colors are the result of some light source and how that light is absorbed and reflected. Above water, light is not usually absorbed significantly, but light source colors can vary. For instance, indoor fluorescent lighting can be a harsh white, or some lights can be orangey.

To account for this, cameras allow you to change the white balance. This redefines what the camera thinks of as white by allowing you to intervene with your knowledge. If you know a wall is white, but it appears yellow because of the room’s lighting, you can point your camera at it and “tell” it that “this is white”. The camera will then shift internally to account for this. If the camera were a person, it would say, “Aah, this wall looks yellow, but is actually white (my owner told me so). This means everything in the room is going to look a little yellow. I will compensate for this by removing yellows.”

Underwater, we are doing the same thing, except instead of compensating for off-colored light, we are adjusting for red light frequencies being absorbed. When we tell the camera that something is white that looks blue, the camera adjusts by removing blues.

I hope this helps your understanding of white balance. The best way to understand it is to play around with it. Get out your camera manual and play, even above water. If you don’t have your manual, look for it online at your camera manufacturer’s website. Try silly things, like pointing to a blue wall and setting manual white balance. What does is do to your pictures? Think about what it will do first, then try it and see if you were right.

So often in our haste to take pictures underwater we forget an important fact: to be a good underwater photographer, you first have to be a good diver. The good news, however, is that being an aspiring photographer doesn’t have to interfere with your development as a competent diver. In fact, it often accelerates it.

Many of the skills we develop in life are born out of necessity. Likewise, mastery of fin pivots, for example, may come out of the need to get in close to a photo subject rather than rote repetition. The ability to hover effortlessly may arise out of shooting stingrays and not advanced certifications.

The line is drawn where photography interferes with your ability to be a safe diver. It is your responsibility to consider the factors leading to a dive. If you don’t think you will be able to take pictures without harming the environment or doing so safely (including your responsibilities to your buddy), it is on you to make the call and leave the camera behind.

Usually this is not the case. Enjoy learning how to take photos underwater, and appreciate the side benefits it has on your abilities as a scuba diver. You may surprise yourself at just how competent a diver you become in the process.

Photo by PhotopediaPhotos

Project AWARE has posted a one-page PDF with 10 tips for underwater photographers.

The tips are definitely “Project AWARE”-style, in that they are meant to remind you that taking pictures comes second in priority after not hurting the aquatic environment.

Here are the 10 tips:

1. Photograph with care
2. Dive neutral
3. Resist temptation
4. Easy does it
5. Sharpen your skills
6. Be informed
7. Be an AWARE diver
8. Take only pictures, leave only bubbles
9. Share your images
10. Conserve the adventure

Check out the PDF if you’re interested and have a few minutes to spare.

I don’t have a fish ID article today, so instead I offer a link to Dive Photo Guide.

Dive Photo Guide is a pretty nifty site about underwater photography. This includes articles on photography techniques. They have monthly photo contests and a section listing underwater equipment options.

It has stuff for the non-photographer. In particular, check out the Galleries section for some great underwater photography; it can be inspiration for those of you who do take pictures.

Have a great weekend and I’ll see you on Monday!

In underwater photography, backscatter is light that reflects off particles in the water resulting in specks of light in the photo. Usually this light comes from an on-camera flash, although any bright light from the direction of the camera can do it. Particularly unclear water can exacerbate the problem.

There are mainly two ways of addressing the problem:

1. Don’t use a flash / strobe from too far away

   “Too far away” is dependent on the visibility of the water, with higher visibility tolerating flash from slightly farther distances. However, anything above 3 ft / 1 m will probably have backscatter.

2. Separate the camera and the strobe

   This can be problematic, since for most point-and-shoot cameras, an on-camera flash is your only option; only mid-range cameras and SLRs support separate strobes.

   
   To correctly light photos without causing backscatter, a strobe pointing at the subject from the right or left of the camera is a huge help. This way, the camera only sees the light that reflects off the subject, and not that which is reflected by particles (since the light is reflected away from the camera lens).

In this photo you can see backscatter caused by my flash going off in somewhat murky water (about 15 ft / 5 m visibility). This picture was taken at Los Coronados Islands near San Diego, California.