Most top-side DSLR / Mirrorless photographers appreciate the importance of having several lenses for different types of shots. A basic photography kit usually includes a wide angle lens, a telephoto zoom lens and perhaps a couple of prime lenses.
Switching between lenses on ground is pretty easy, but underwater, we don’t have that luxury.
Even if you’re shooting with a compact above water, you can always take a few steps back, or zoom in, to get a different angle or frame. When water enters the equation, things aren’t that simple.
Enter Wet Lenses!
Wet lenses were developed as a method of altering the field of view or optical quality of our original lens, without the need to surface. Hence the name – Wet Lenses!
Wet lenses are positioned in front of the underwater camera housing, flush against the port. They are usually designed to take into account the layer of water between the front of the port and the back of the lens, since water combined with air creates some type of optical element.
The main advantage of shooting with compact cameras underwater is versatility. The option of using wet lenses and changing them during the dive allows you to shoot a Whale Shark and a Nudibranch on the same dive! Something that can rarely be achieved with even a DSLR underwater. This is the reason some photographers prefer leaving their DSLR’s above water and getting a 2nd compact system dedicated for underwater use.
Let’s go over the main features of wet lenses:
Types of Lenses
The 2 most common types of wet lenses are Wide Angle and Macro (aka Close-Up).
This is derived from the 3 types of underwater photos – Wide Angle, Medium shots and Macro. Medium shots are also known as “Fish Portraits” and don’t require special lenses, since your average camera lens will usually be the ideal focal range to shoot that type. The other two are the ones we want to improve on. As long as you’re changing your FOV (Field Of View), you would probably want to go wider or get closer.
Mounting a wet lens on your housing can be done in several ways and is generally determined by the type of mount the housing offers. Some methods can be combined or replaced using various adapters.
Thread Mount (Screw-on lenses)
The most popular method is threading on the front of the port, 67mm and 52mm are the most common thread sizes. With this method, the lens has similar threading and can simply be screwed on the front of the housing. If the threading on the lens and the port are different, a step-up / step-down ring is used.
The Bayonet mount is a common attachment type in many industries, due to the simplicity of attaching something with this mechanism. It requires a simple “1/4 twist and press” action, which is usually locked in place with a button, lever or spring. It was quickly adopted underwater, to prevent unnecessary fiddling with the gear and making the lens replacement as simple as possible. The problem is that the standardization of this type of mount is not uniform among different manufacturers, and many of them tend to develop their own unique type of Bayonet, which doesn’t play nicely with other types.
Flip / Swing Mount
This is not a method by itself, but usually combines a thread mount along with a swing or flip mechanism to position the lens in front of the port or get it out of the way fast. This is by far the fastest and easiest way to switch between different FOV’s but it’s mainly effective for close-up lenses, since wide angle lenses are heavier and require more precise positioning.
The adapter itself can be pricey and if it’s not high-quality, it can swing / flip out of place involuntarily, which can be quite annoying. Nevertheless, it’s a valuable asset and very common among macro photographers.
Some manufacturers create their own mount types for lenses, such as Fantasea’s excellent snap-on mechanism for the G7X / G16 housings. These custom mechanisms are usually very good and easy to use, but would limit the user to one type of wet lenses, made by the housing manufacturer.
How does it work?
Wet lenses consist of one or more optical elements and rely on a specific type of lens which they are to be mounted on. As mentioned before, they take into account the thin layer of water between the port and the lens, to deliver optimal quality and sharpness throughout the frame. Naturally, some lenses use higher quality optical elements, which raises the final price for the customer. They vary in size, weight, shape, contrast, sharpness, vignetting, corner sharpness, fringing and more. Not all lenses are created equal and not every lens is intended for all housings, or all photographers for that matter.
Wide Angle Lenses
If you’re a diver, or even a snorkeler, you have probably noticed that things look bigger underwater. This is caused by optical refraction between air (in your mask) and water. The same thing happens with your camera. The housing serves as a “mask” for the camera, causing it to see things bigger, which is translated to a narrower Field of view, just like zooming in. The change in FOV varies but we can regard it as approximately 25%.
A wide angle wet lens is meant to fix that, or even produce a wider field of view, such as FishEye or Ultra Wide.
Dome vs Actual Lens
There are two types of wide angle lenses for underwater. The first one is simply a dome, made out of acrylic or glass, with trapped air inside. This type of lens has no actual optical element, so if you look through it above water, you won’t see any difference, but when it goes underwater, the magic starts to happen. The dome combined with optical refraction creates a virtual image on your camera which eliminates the 25% difference in FOV and returns the focal range to that produced on the surface. In short – adding a dome creates a 25% wider image underwater!
The second type is an actual lens with one or more optical elements. Usually a wide angle lens is comprised of several optical elements, producing a definitive angle of view which is mentioned in the manufacturer specifications. These lenses will usually work both underwater and above, producing a certain FOV underwater and an even wider one above water. Some lenses will actually produce a FishEye angle, which is very wide and can reach up to 180 degrees. However, to reach a 180 degree FOV underwater, you will most likely require a dome port in addition to your wide angle lens, installed in front of it.
Some wide angle lenses, such as the popular Inon UWL-H100, have an optional add-on dome which can be purchased separately and installed in front of the lens itself, increasing FOV and significantly improving corner sharpness.
Compatibility note: Wide angle lenses are engineered to fit a specific focal range on your original lens, such as 35mm or 28mm on the newer ones. Recently released compact cameras feature an ultra wide 24mm focal range, making it increasingly hard to produce wide angle lenses that fit without vignetting (black corners). As a result, you might need to zoom in slightly when using wide angle wet lenses on newer compacts, to avoid black corners (alternatively, you can crop in post processing).
Macro / Close-Up Lenses
This is probably one of the most popular additions to underwater camera gear. The underwater world is abundant with small critters which are both magnificent and bizarre. Taking photos of these wonderful creatures and enlarging them for the world to see, is one of the underwater photographer’s main goals and passions.
To create this type of magnification, all you need to do is get close to the critter, zoom in as much as you can, and shoot! Sounds easy right?
The problem is focusing.
Every camera lens in the world has a limitation called minimum focus distance. This is the closest you can shoot from a subject while still keeping the image focused. When zooming in, that distance grows even further away, making it impossible to get a sharp clear shot of the critter. Close-up lenses, aka macro lenses, aka diopters, are placed in front of the lens, altering that “minimum focus distance” and reducing it significantly. The effect is usually measured by +X units (+4, +6, +10, +15…). This is a relative measurement, which depends on the original lens. The longer the zoom of the original lens is, the more magnification you will get in the final shot.
Macro photography is generally considered getting your subject to have a 1:1 size ratio on the sensor. That means a 1/2″ critter will take 1/2″ of your sensor. Assuming it’s a 1″ sensor, a 1/2″ critter will take up half the frame.
While this is the “proper” way to determine exactly how much magnification you are getting, with all due respect, we are not scientists! We’re just a bunch of people who like taking photos. We don’t need exact figures…
What you need to remember is this – More Zoom + Stronger Close-up Lens = More Magnification
An important thing to keep in mind – the more magnification you produce, the smaller your DOF (Depth Of Field) will be.
DOF is the range that is in focus. When shooting macro, it can be as small 1mm (a bug’s eye), causing the act of shooting the photos quite an excruciating feat. You will usually require a lot of practice, excellent diving skills and quite a few tries to get one shot right.
Beginners are advised to start out with a lower magnification lens (+4 or +6), until they get the hang of it and can advance to the +10 or +15 lenses.
Insect View Lenses (aka Micro FishEye)
The last type is an odd combination of both previous types. It’s an Ultra Wide Macro lens! That means that’s it’s intended for close-up shooting, while capturing a very wide frame behind the main subject. This type of photography is called CFWA (Close Focus Wide Angle). You can create CFWA with standard FishEye lenses, but this one takes it to extreme.
The end result is very unique and cool, allowing you to demonstrate to your viewers how the underwater world looks like from the eyes of a bug.
Inon produces the most popular insect view lens – the UFL-MR130 EFS60 lens as well as the less extreme UFL-M150 ZM80 lens.
Common Compatibility Issues
Due to the large amount of manufacturers in the market, both for cameras and housings, as well as wet lenses, compatibility is something you should take great care with.
The easiest solution is to get a lens made by the same manufacturer as the housing. This will likely ensure compatibility and usually easy to figure out which lens you need for your housing.
If your housing manufacture does not produce wet lenses, you can usually find online which are the wide angle and macro lenses that are most recommended for your camera and housing. Our UW photo experts have a lot of experience with this, so it would be best to ask us!
Common issues which you might encounter are:
Vignetting (Black corners) – This is a problem which occurs in wide angle lenses, that are engineered for a different focal range than the one you’re using (e.g. wet lens made for 35mm, used on a 28mm lens), or if you’re using an adapter for matching different mount types, or adding a filter behind the wet lens, which causes the lens to be further away from the front port than intended.
Vignetting with Macro Lenses is not a problem! It simply means that you didn’t zoom in far enough on your camera. Zoom in all the way and the black corners will vanish.
Vignetting with Macro Lenses is not a problem!
Black sides – This might occur if your wide angle lens has a shade, which is misaligned. Make sure the larger flaps of your shade are on the top and bottom of the frame, and the smaller flaps (if there are any) are on the sides.
Trouble Focusing – Some lenses will require switching to Macro Mode on the camera (little flower). Mostly on underwater domes such as the Fantasea BigEye. This is because of the virtual image I discussed previously, which is created close to the lens and the camera needs to focus on that.
When using a macro lens, your focus range is limited, so you would need to get used to the closest and farthest distance from which you can shoot your subject.
Soft corners – Some wide angle lenses will cause the corners of your frame to be blurry and soft. This happens as a result of forcing optical elements to work together even though they are not aligned in an optimal way. Using a dome on your lens will help, but the best solution is closing down your aperture. This will reduce the problem significantly.
Strong purple fringing – Some purple fringing always exists in every lens and it’s not always noticeable. The higher quality your lens is, the less fringing you will get. Fringing can be either fixed in post processing (Lightroom does a great job on this) or simply getting a better, higher quality lens.
Most of these issues can be resolved by switching over to a professional underwater camera and not using wet lenses. That, However, requires a much higher budget, more travel weight and is at a higher level of complexity.
Apart from the actual wet lens, there are several useful accessories which can be added to your system for increased comfort and usability.
Lens holders are an excellent addition which enables you to stow your lens on the tray or arms when not in use. These can be found for various types of arms and various mounts. Just look for the one that matches your gear. Using a lens holder is a good alternative to stuffing the lens in your pocket / BCD / wetsuit thus preventing potential damage to the lens.
Flip / Swing holders, which I mentioned previously in the Mounts section, are a useful add-on which can help you apply or remove the lens in the easiest way possible, instead of screwing it all the way in or out between shots.
Dome shades are a nice little add-on which is available for some lenses and reduces flare from the sun, enhancing the overall contrast of the image.
Filters can sometimes be combined with wide angle lenses for better results when using ambient light. Red or pink filters are quite common for correcting the colors underwater and some wide angle lenses allow the use of filters behind or in front of the lens. Keep in mind that this might reduce sharpness since the lens is not used exactly as intended, so it’s not always recommended.
Popular Wet Lenses in the market
(Updated Oct 2019)
Fantasea AOI UWL-09F | US$699
High quality wet wide angle lens, with excellent optics and dome port, for optimal image quality underwater. Compatible with a 67mm thread mount, ideal for compact cameras such as Sony RX100 series and Canon G7X series. Expand your FOV (Field of View) to 130 degrees on a 28mm lens!
Nauticam’s Wide Wet Lens 1 is the result of extensive R&D and excellent engineering.
“WWL-1 is the highest quality wet changeable underwater wide angle conversion ever made, featuring unmatched contrast, overall sharpness, corner sharpness, and clarity”.
The WWL-1 can be fitted with a 67mm threaded mount or on a dedicated Bayonet mount.
Fantasea BigEye | US$219.95 –US$299.95
The Fantasea BigEye is a dome only, designed to restore the focal range lost due to optical refraction, effectively adding about 33% wider field of view underwater. It comes in a variety of models to fit different Fantasea or Canon housings and is a great affordable option for getting that entire shark in the frame!
The BigEye is available as a snap-on for Fantasea / Canon housings and threaded for 67mm housings.
Kraken KRL-02 | US$449
The KRL-02 is the newest lens by Kraken. It includes both a wide angle lens and a dome unit for about half the price of the Inon or Nauticam alternatives. It’s designed for a 52mm thread, so 67mm threaded housings will require quite a lot of zooming in, sometimes rendering it useless. However, for the smaller compacts such as Olympus, it’s the perfect lens!
The Inon UWL-H100 has been the market leader for many years now, since its release. The compatibility with 28mm lenses, the excellent sharpness throughout the frame, the availability of the Dome Unit II for extra wide angle and even better sharpness; all of these have made the UWL-H100 a top choice among compact shooters.
Ikelite W30 | US$475
The W30 is a great solid lens, created to fit most of Ikelite’s compact housings (fits a 46mm or 67mm thread). Specifically designed for digital cameras with 28mm focal length. It’s also possible to use it on any other non-Ikelite housing with a 67mm thread!
Inon UCL-165 | US$165
This popular +6 lens has been a top choice among beginner underwater photographers for the past few years. It features excellent sharpness and contrast, ideal medium range magnification – enough to make the critters pop, but not too much that it becomes harder to shoot.
The great thing about it, is that it’s double threaded (on both front and back) so once you gain more experience in macro shooting, you can add a second lens, stack it on the first, getting a +12 magnification factor for extreme close-ups!
Nauticam CMC-1 | US$320
Nauticam’s CMC-1 was released in 2015 and designed to become the strongest and most high-end close-up lens in the market. This is the SMC’s little brother, engineered for optimal results on compact cameras.
With a staggering +15 magnification factor and razor sharp quality, this small lens delivers! It definitely won’t be easy for beginners to control it, but once you get the hang of it, prepare to be amazed by the results! Nauticam also offer the less powerful CMC-2.
Kraken KRL-06S | US$195 – US$225
The KRL-06S is not your average diopter. It’s an ultra powerful, super-macro, mind boggling +23 diopter. It can capture a stunningly sharp macro shot of a blenny’s eye. That is, if you are skilled enough to take that shot… Shooting with such a powerful diopter is no easy feat. It’s designed for experienced shooters and works best with a longer DSLR zoom lens such as the Nikon 105mm or the Canon 100mm. This lens isn’t compatible with most compact cameras.
Nauticam CMC-2 | US$290
The Nauticam CMC-2 is a new macro lens designed to stand alongside the previous CMC-1, offering a less powerful lens choice for larger macro subjects that is noticeably easier to use.
The CMC-2 ships with the common 67mm threaded lens mount. The lens has a protruding rear element, designed to place the accessory optic as close to the camera lens port as is possible, providing the best overall image quality when used with flip lens adapters.
Fantasea AOI UCL-05LF | US$179.95
Fantasea joined forces with AOI to create 3 excellent high quality macro lenses for various subjects and magnification levels. The UCL-05LF is a +6, the UCL-06LF is +12 and the UCL-09F is a +12.5 super macro lens with maximum magnification.
All lenses use high quality optics and produce sharp, vivid images.
Mozaik +8 Close-Up lens | US$149
If you’re looking for an affordable and strong magnification lens, this would be the best choice! This excellent +8 close-ups lens delivers the best bang for your buck and fits any 67mm threaded port.
I hope this article helped clear up a few things!
If you have questions about anything I discussed here, or anything else for that matter, feel free to reply to this post or contact me directly at firstname.lastname@example.org
Dive safe and mind your fins!