In this article:
- Why Use Color Correcting Filters?
- How Do Color Correcting Filters Work?
- Mounting a Color Correcting Filter
- Choosing Your Color Correcting Filter
- Is a filter really my best option?
Why Color Correcting Filters?
Though Roy is not a real person, you may want to learn and remember how he was given his name. Roy G. Biv is an acronym for Red Orange Yellow Green Blue Indigo Violet - the colors of the rainbow. It's not just the colors we underwater photographers want to remember, it is the order in which they make up Mr. Biv's name. It is also the order that they fade as we look through water. At the beginning of that list is red, and red is affected more than any other color through water. Next is orange; orange is not affected as much as red, but it is affected more than all of the other colors. Next is yellow and so on.
We will explain the relative effects of color change of light travelling through water based upon an article published by Texas A&M's Department of Oceanography.
It is fairly well documented that after travelling through 1 meter (3 feet) of "coastal ocean water," blue light will still have 90% of its intensity, but red light will have only 60% of its intensity. The blue light, relative to red light, is approximately 1+1/2 times 'too strong.' You should be easily able to adjust for that differene in the camera with 'white balance' adjustment.
Studying the charts further, let's look at the relative strengths of light after travelling 10 meter (33 feet) through the same pure ocean water. Blue light will have 35% of its intensity remaining, but red light will only have 0.6% of its intensity remaining. After travelling 10 meter through 'coastal ocean water' the blue light will now be relatively 58 times more intense than red light!
But, I Just Poured a Glass of Water and it is Perfectly Clear; It's Not Blue!
Your glass of water just is not big enough to have enough effect that you can readily see it. No matter how clean your water is, if you have enough of it, it will appear blue. All water absorbs light according to the rules of Roy G. Biv.
Have you ever noticed that swimming pools are always painted blue? They are painted blue so that the homeowner will expect the pool to look blue. If the pool was painted white and then filled with water, the homeowner, expecting the pool to look white, would be very upset to see that his just-filled-up-today-with-clean-water-pool appears... you guessed it... blue!
It's about distance, not depth!
During our open water scuba diving course, most of us are taught that 'the deeper you go, the more color is lost.' That is true, but it is not complete. Us divers know that the deeper we go, the darker it is. So we like to take a dive light with us. Not only will it help us see better, it will help us see the beautiful colors of all that underwater life.
The farther the light travels the more the color of the light is changed. This is why deep water looks deep blue and shallow water looks clear.
Roy G Biv explains why a coral at 90 feet deep will have much less red, orange, yellow, than the same coral 10 feet deep. Now think about this situation; how would the colors of that coral look if it were 90 feet deep and you were 90 feet deep and 10 feet away? What if the coral were 10 feet deep and you were 10 feet deep but 90 feet away?
The colors will be identical in both of these situations. Yes, at 90 feet deep, the coral will be much darker than at 10 feet. If you set your camera exposure perfectly for the coral in each case, you will see the colors of the coral looks identical in both images (the background water will of course look much different).
Regardless of what depth you and that coral are at, the farther away you are, the more the color is changed. That's Roy G Biv and you can not change physics.
The main point here is to always think of water's effect on color as an effect of distance, rather than just an effect of depth.
When you think of water's effect on color as being caused by distance, not depth, you can understand why, when at depth, the 'far end' of the wreck will look different than the 'close end' of the wreck. When you hover 100 feet above the wreck, looking straight down, both ends of the wreck will look the same.
It is distance that affects color, not depth! Because of this effect of physics, it is not possible to have any type of filter or camera white balance that can simultaneously compensate perfectly for both near subjects ('this end' of the wreck) and distant subjects (the 'far end' of the wreck).
Granted, it is a lot easier to talk and write about filters by using the term 'depth,' which we will do here. But you know the whole truth.
What Can We Do to Get Colors Back in Our Underwater Images?
There are several options to improve the color of our images.
- Add artificial Light
- Adjust the camera's white balance
- Use a color correcting filter
- Use a combination of a color correcting filter plus white balance adjustment.
This article is about color correcting filters, not artificial light, so we will only cover options 2, 3, and 4.
How Do Color Correcting Filters Work?
By reducing the amount of blue light (and green, indigo, violet light) so that it is more equal to the amount of available red light (and orange and yellow). This means that your camera will have less light to use for focusing and will have less light for exposure. This is why color correcting filters are only recommended for daylight dives and reasonably shallow.
We will rephrase that; color correcting filters work by reducing the amount of light of BIV colors They do not 'restore' the ROY colors. Color filters reduce the amount of light getting to your camera. To compensate you will need slower shutter speed, or larger aperture, or both. When overall light is low, a color correcting filter will make photography extra difficult. For all cameras, there is some 'depth' at which the camera will not detect any red light at all; none, zero, zilch. At that 'depth' and below, no correcting filter can help.
But you can make up for the focus problem with a video light or strobe, correct? No. The filter will also filter light from your light which will result in the artificially lit area looking like a bright red light on your subject. Keep in mind what we said earlier; do not use any artificial light when using any color correcting filter.
Shooting with Color Correcting Filters
While there are multiple manufacturers of color correcting filters for underwater photography, we would like to recommend this article by the manufacturer of Magic Filters; Photographing with Filters Underwater is short, easy to understand, and has plenty of example photographs (and some video also).
The second and third 'rules' for using color correcting filters are 2) sun at your back and 3) shoot down at a 45 degree angle. For those of you that have read this far, 'rule' #1 is watch the Shooting Magic DVD.
Join underwater photographer and inventor of the Magic Filter, Alex Mustard, in the Red Sea as he personally guides you through the techniques of filter photography underwater, with both digital SLR and compact cameras. This DVD demonstrates and explains the best methods for using the Magic Filter color correcting filters.
Shooting Magic DVD
When to Use Color Correcting Filters
Once you understand the purpose, function, and limitations of color correcting filters, you will be able to decide for yourself if a filter is likely to help you attain the shot you desire. In very shallow water you may be satisfied with the results obtained by adjusting the camera's white balance or your adjustment in post processing.
One bit of advice that is always true; do not use a color correcting filter in combination with artificial light (strobe or video light).
Choosing Your Color Correcting Filter Mount Type
The most important factor in choosing the correct color filter is not its color, but its method of mounting. Because if you can not mount the filter, it does not matter if it is the optimum color response.
The Basic Types of Color Filter Mounting Underwater are:
- Wet mate filters
- Internal1 flip-mount filters
- Threaded filters mounted on front of lens
- "Gel" filters mounted on back of camera lens
1In the context of this article, "internal" means internal to the underwater housing.
Wet mate threaded filters screw onto the front of a housing's lens port. This can only be done for flat ports which restricts the filter use to macro and medium wide lenses. Wet mate filters can also be mounted into 67mm flip holders permitting underwater selection of filters. Note that most filters are meant to be mounted on the lens and can not be used in water.
|A Threaded Filter for Use In Water (External Mounting)||An Ikelite Push-On Wet Mate Filter|
Threaded filters which mount on the front of the lens are easy to install but can not be removed underwater. You will need to make the decision whether to use a filter before installation of the lens port. In rare instances, you may find that there is not enough clearance between the lens and the flat port to install a filter.
Ikelite push-on filters are available to fit the port of all Ikelite Ultra-Compact and Compact underwater housings. They also manufacture filters which can fit onto Ikelite W-20 and W-30 wide-angle wet-mate lenses. Recent Fantasea BigEye ports for compact cameras are designed so that the filter is mounted to the back of the wet mate dome port. This enables the photographer to install or remove the filter while underwater.
There are also wet mate filters that snap on to the housing. This is common for compact camera housings like Canon housings for the S or G series cameras.
|Wet Mate Filter for Canon Underwater
Housings for S Series Cameras
|Wet Mate Filter for Canon Underwater
Housings for G Series Cameras
Internal flip filters are often seen in underwater video camera and camcorder housings. The manufacturer provides a control on the outside of the housing which places the filter between the lens and the lens port or moves it out of the way when not needed.
Internal Flip Filter in a Light & Motion Camcorder Housing
Threaded filters which mount on the front of the lens (internal filter) are easy to install but can not be removed underwater. You will need to make the decision whether to use a filter before installation of the lens port. In rare instances, you may find that there is not enough clearance between the lens and the flat port to install a filter.
'Gel filter' describes a filter that is similar to a sheet of colored plastic. They are available for many purposes in many sizes, in sheets, and in rolls. Some gel filters will be rugged, thick, and rated to handle high temperatures of studio lights. Gel filters for lenses, however, will be thinner, a bit more delicate, and available with very precise color transmission properties. Some gel filters can be damaged if mounted to the outside of the housing during underwater use.
Gel Filters for Point-and-Shoot Cameras
Canon, Panasonic, Fuji, and other camera-branded housings for compact cameras typically have ports specifically designed for that one camera. Unfortunately, this means that without an additional adapter it is not possible to mount any standard wet mate filter such as a 67mm or a push-on. One solution is to add an Inon 'mount base' for the housings that will allow mounting of standard AD, LD, or 67mm lenses and filters.
If you choose not to add a housing specific mount adapter, you may still use a gel filter. You can cut the gel filter to either mount on the inside of the housing port, or tape it to the front of the camera lens.
Gel Filters for Fisheye and Very Wide Angle Lenses Interchangeable Lens Cameras
"Gel" filters are the only valid choice for fish-eye lenses and very wide angle lenses. Because the glass of these lenses protrudes beyone the 'frame' of the lens it is not possible to use a threaded mount filter on the front of the lens. Additionally, because fish-eye and very wide angle lenses require a dome port for the housing, usually no filter can be wet mate mounted.
For these lenses, gel filters mount on the back of the lens (the end that is mounted to your camera body). Some lenses have a filter mount built in. Some lenses do not, which will require that the filter be taped to the back of the lens.
Filters are available pre-cut to perfectly fit in the filter holders of many lenses, but not all. For these lenses, you will cut the filter to size.
Unless you are sure what type of filter should be used with your lens, please contact us. We will research your lens so you get the correct filter type the first time.
A wide selection of wet mate color correcting filters are available for GoPro Hero video cameras. Though the lens itself is prominently curved, the dive housing has a flat port. The flat port reduces the angle of view significantly, but does allow installation and removal of filters while underwater.
Use the red filter for videography in clear blue ocean water at depths of 15 to 70 feet. Use the magenta filter for videography in 'green water'.
GoPro™ Red Glass Filter on GoPro® Dive Housing
For Use in Clear Blue Water
GoPro™ Magenta Glass Filter on GoPro® Dive Housing
For Use in Green Water
Color Correcting Filter "Colors"
To keep this article simple, this section will explain choice of filters by three basic filters offered by Magic Filters. The concepts apply regardless of brand or style. However, most suppliers of color correcting filters for underwater use do not offer more than two choices.
Auto-Magic Filters for point-and-shoot
- These include cameras and camcorders that do not give you the ability to adjust white balance; cameras that do the color adjustments automatically.
- Orignal Magic Filter
- These filters are designed for DSLRs, mirrorless, compact cameras, and camcorders that do allow give you the ability to adjust white balance.
Green Water Magic Filter
- As with the Original Magic Filter, these filters will yield best results when used in combination with proper manual adjustment of the camera's white balance. The filter has been designed to give better performance in 'green water' compared to other filters.
Let us clarify what we mean by point-and-shoot cameras. Point-and-shoot cameras are those that do not provide any means for the user to adjust shutter speed, aperture, or white balance. When we refer to compact cameras, we are describing cameras that do not have interchangeable lenses, may be as small as a point-and-shoot, but do allow the photographer to adjust shutter speed, aperture, and white balance.
Point-and-shoot cameras typically have very small sensors. Small sensors mean that they do not gather much light. While this is not a factor in most topside photography, it can mean that when underwater as little as 10 feet that the camera sensor may not detect any red light at all. Other point-and-shoot cameras will perform well with a color correcting filter as deep as 45 feet.
The engineers designing point-and-shoot cameras have programmed the computer in the point-and-shoot camera to make all of these adjustments automatically for you. While this works very well in air, it can result in mediocre to terrible colors underwater. The Auto-Magic filter color transmission characteristics have been designed with this in mind. They can make very dramatic improvements in your underwater photography. The color characteristics of Auto-Magic Filters give the best all-around performance.
The Original Magic Filter has color characteristics designed to give the best possible image results when the camera has been properly white balanced. This may be done with a white-balance card or port, and should be re-adjusted with every change in depth or distance. It is also recommended that white balance be adjusted when changing the direction of photography relative to the sun. Magic Filters states that the best use of these filters is shooting down at a 45 degree angle with the sun to your back.
Can you use the Auto Magic filter with a DSLR, mirrorless, or compact? Yes. Why would you? If you are not going to be post-processing your images the Auto Magic filter will give you better all around results, though none of the images will be the best possible. If you are diving with constant moving subjects, you will not have time to repeatedly adjust white balance as your depth or distance to subject changes, and especially as you change direction relative to the sunlight.