Friday 4 December 2015

Review: Telesin 6" Dome Port for Gopro

This is a review of the Telesin 6" dome port for Gopro cameras. My use of the dome port in shallow relatively quiet water is probably very different  to your intended use so please keep this in mind when reading on.

Dome ports enable you to get those great split or under/over shots where you can see both under water and above water at the same time. They can add a whole new dimension to your photography and video.

I was excited when I saw these first dome ports come on the market for gopros, but I just couldn't justify the price of the KNEKT KSD 6 or SPL models for my limited use. I explored a few options of building my own as several have done on youtube  and elsewhere online but then put the idea on the backburner for a while.

Recently I discovered online that a much cheaper dome had been produced – the Telesin 6" Dome Port – and despite some mixed reviews on Amazon, I went ahead and ordered one through the Ebay seller dadahkstore. At AUD $115  and about a quarter the cost of the KNEKT dome and handle it seemed like a bargain, considering the acrylic domes alone, without any drilling, handles, backing etc retail for around AUD $60.

To date I've only used the dome on a couple of occasions mainly just to test it, and so far I'm very happy. The Telesin 6" dome port has several limitations compared to the much more expensive models, however for the price and non-professional user, and depending on the intended use, I think it is a great buy.

Here's what I received in the box:

  • the dome port with attached backing plate and "gopro" waterproof housing
  • a yellow plastic bobber handle with gopro connection and screw
  • a microfibre cleaning cloth
  • a blue lightweight wrist strap
  • an allen key to remove the screws on the dome port if required
  • cardboard box with fitted foam insert to protect the dome port*
*Do not throw the box and foam insert out. Like all acrylic, the dome can be very easily scratched, so unless you have a better option available, keep the dome stored in the foam inside the box and be meticulous about sand and dirt.

Different views. Note the curvature of the dome in profile, not quite a full half sphere and the black camera faceplate with red seal. Also note for this photo I have the handle on backwards.



Some details: one of the 12 screws holding the dome port to the backing plate, and  detail of the front lens of the gopro housing. Note the red seal behind the screw in the far left image. Middle image shows rear view of screw from backing plate. Right image shows inside the dome. Note how the camera power on/off button is covered and front camera display  is covered.

I was a little concerned about what actual model of dome port I would get as there are several different images available online. Some with blue, some with black inside the dome. Also some seem to be half spheres in profile, others seem to be less then half spherical in profile so it was a bit of a lottery. Even the Telesin website does not show the difference between versions or the latest model.
What appears to be an older model in many images online. Note the blue camera face plate, very different curvature of the dome (a full half sphere) and the phillips(star head) head screws. Even some of the sellers online have images of different domes so it's hard to be sure exactly what you are buying.



I was concerned about getting reflections off the screws and retaining plate or the Telesin namebrand but to date haven't had any problems. I am still very surprised why the whole inside of the backing plate is not a matt black to ensure no reflections as in the more expensive domes.


First impressions

Considering the price, I was impressed by the build quality – much better than what I could have done myself. Off course some things could be better, but for the price I'm happy.

The "gopro" waterproof housing looks like a new Hero 4 series gopro housing but I have my suspicions it's not. My Gopro Hero 3 fits comfortably inside, but I would thoroughly test the housing underwater without the camera before you use it. The housing is glued onto the dome backing plate so can't easily be replaced. There is a single latch with no safety catch to close the housing and a short string to help you open the latch.

The only attachment point to the bobber handle is the standard gopro like fitting. This is fine and sturdy for just a gopro, but when you stick a big heavy dome port on it, with an enormous amount of resistance and bouyancy in the water, you create a lot of leverage at this point and I have my doubts if it will be durable enough in the surf or rough water. To allow for the camera lens to be in the centre of the dome, the bobber handle is off the centre axis. For my intended use though it's fine.

PROS

  • good build quality for the price, cheaper than DIY
  • easy to use and assemble
  • great results when used at the surface of the water
  • white horizontal line on backing plate makes for easy leveling/half-way reference
  • foam insert and box is good for storage and transit

CONS

  • no access to camera power on/off button when in dome port
  • cannot see front camera display when in dome port
  • without red LED's turned on, you cannot tell if the camera is on or off
  • although I've had no problems yet, I'm concerned that the mounting point is too weak to use in rough conditions and could perhaps break in the surf or if used at any depth.
  • if the gopro housing is damaged or develops a leak it would be very difficult to replace
  • poor information available on web regarding the actual model/versions available


Using the Telesin dome port

One very important point you need to be aware of with this dome is that there is no access to the power button on the camera. This means that you must power on your camera before you put it into the waterproof housing. You cannot view the front display on your camera whilst it is in the housing, so unless you have the red LED's set to flash, then you have no way of knowing if your camera is actually on. If you plan to use the dome for photography, then you must go into your camera settings menu and ensure that the camera is not set to turn off automatically after 60 seconds or so. When taking photos I have just set the camera to timelapse mode so that it takes a photo every second or so and hence it won't turn off. If you are doing video then you need to start recording before you put the camera in the case and leave it running for the whole time you are in the water. It also means that you can't switch between video and photos or any other settings unless you open the back of the housing and remove the camera first. This is a big difference to the KNEKT KSD 6 where you can access the power button and see the display on the front of the gopro whilst it is in the dome port.
 
As expected the dome is very buoyant. I only intend to use it for surface use but did test it briefly down to 2m and it held up ok without leaks, although I held onto the edges of the dome itself and not the handle at that depth as I didn't have great faith in the handle mounting point. For use on the surface in mild conditions the handle was fine, although I wouldn't want waves in the surf to be hitting it. I would like to see the dome with a much more rugged mounting to the handle, preferably to the backing plate and not just the gopro housing, but remember this is a cheap dome!

When raised quickly out of the water, water seems to bead off the dome ok, but for extended use you probably want to spit on it and rub it on the dome – I've heard Rainex is not good to use on acrylics. You need to clean the outside of the dome thoroughly before each session, salty water can quickly dry and leave marks, as can sweaty fingers, sunscreen slicks in the water etc.

A clear white horizontal line on the backing plate makes it easy to judge what is level and halfway in the water and is very useful.

Domes work best in clear water with a light substrate as in this situation there is not a big exposure difference between above and below the surface. Remember your camera will try and balance the overall exposure to an 18% neutral grey. If the water is much darker than the sky, the camera will think the image is underexposed and so expose the image for longer, resulting in blown out skies without detail. With a gopro you have no control over this apart from using external factors such as how much of the image is in the water and how much is out. It comes down to trial, error and experience.

All the photos and video stills below are straight from the camera with no adjustment apart from resizing for the web. The photos were taken by using the gopro in timelapse mode so a photo was taken every second or so.

It's very easy to overexpose the sky and loose detail on split shots. This was taken looking towards the sun. Try to avoid high contrast areas for the best shots.
Taken with the sun on my back, there is much less contrast in the image resulting in better exposure with all detail maintained. Of course the image could be vastly improved with a quick adjustment in photoshop, but all these images are straight from the camera apart from resizing.
Although the metal grid appears razor sharp above the water, it appears slightly out of focus underwater – a result of the virtual image created by the dome being slightly too close for the gopro's focal range. It is not an issue caused by this dome, it is an issue with all domes.
Another example: hand sharp above water but slightly soft below.



Although the water is very clear, it's also dark so the camera calculates to overexpose the image resulting in the blown out sky and loss of all detail. Too much contrast for the camera to handle.





Below are 2 video stills taken from 1080p video on the Gopro Hero 3 using the Telesin dome port in a shallow freshwater stream. There have been no adjustments made for exposure, contrast or colour, the images have only been resized for web use. Note that I deliberately tried to block sky views to allow for a more balanced exposure under the water. The gopro was set to medium view mode. Note that there are some water droplets on the dome port.




Dome Port Theory

There is quite a bit of physics at play when using dome ports for over/under shots due to the way light travels through different mediums (air and water) and the role of refraction in creating a virtual image some distance in front of the underwater part of the dome. That distance is determined by the radius  of the dome and the thickness of the acrylic.

From my limited understanding, the virtual image underwater is created approximately on a plane which lies 4 times the radius of the dome in front of the backing plate/camera lens position. For a 6" dome (ie with a radius of 3") that means that the virtual image is created approximately 12 inches in front of the camera. This is closer than the gopro is able to focus so the underwater part of the image never looks quite as sharp as the above water parts. DSLR photographers using expensive large domes are able to refocus their cameras and the position of their lenses to allow for this virtual image, however, being a fixed focus camera, on the gopro this is not possible. The smaller the radius of the dome, the closer the virtual image is created and this seems to explain why the curved lens housing on the early model gopros was never able to obtain sharp focus underwater.

Here are some links to interesting articles on dome port theory.

An old article from Stephen Frink but still very relevant and a good read.

Scroll half way down here for a good short summary 

and here for a very technical explanation of dome port theory  

I will post some video shot with the dome port here and on my Youtube channel at a later date.

Summary 

Provided you are a casual user and aware of some of the limitations and workarounds, the Telesin 6" gopro dome port is great value for the price. It will add a new dimension to your photography and video, and provided  you use it in nice clear water, will reward you with some great images. For what I intend to use it for, it suits me very well and I'm happy with my purchase.


 


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