SONY RX100 with Ikelite Housing - Dome port? wet lens? what to buy?

Hello divers! I am trying to read as much as possible about underwater photography but my head is flooded with too many information and more I read, more I am scared I will spend  much money and buy the wrong stuff!

I have currently the Ikelite housing # 6116.15 ( in the link below ) and I have a SONY RX100 camera. I know that point & shoot cameras are not the "best" for maximum pro like results but I since I have what I have, I need to work with it. I want to squeeze the best I can with what this camera and then maybe in 1 or 2 years I will upgrade my camera and buy a DSLR/mirrorless  

My housing: https://www.ikelite.com/products/underwater-housing-for-sony-cyber-shot-rx100-mark-iii-mark-iv-mark-v?_pos=2&_sid=814655a78&_ss=r

Correct me if I am not wrong, If I want to shoot mostly sharks, pelagics, reefscapes and wide angle I need to add some wide angle fisheye on the housing and I need to use the shortest focal length possible and zoom as less as possible, right? I hope I am not writing something totally stupid Apart from this I need to strobes, but that's another topic.

So with this housing what would you do to get the best out of it??

I was checking Ikelite site and what do you think about the Ikelite DC2 6 Inch Dome? could this be be the solution? The description says “The Ikelite DC2 6 Inch Dome has been designed to be used with the various Ikelite housings for the Sony RX100 series and Canon G7X. Underwater, the dome corrects for refraction to provide the full wide field of view. That's substantially wider than a flat port, which magnifies the image 1.33x and reduces the field of view. Approximately 3/4 of the camera's zoom range is usable with the dome installed. .” Link: https://www.ikelite.com/products/dc2-6-inch-dome-for-compact-housings?_pos=2&_sid=baef98a72&_ss=r

Or do you think is better to apply a wet lens on the dome ? If yes which one do you suggest would do the job? Ikelite also has a WD-3 Wide Angle Dome. It says that it has a Magnification 0.75x, can anyone please explain how this info is used? it means that if i have my camera at 24mm it actually works as 18mm with the wet lens? It is weird that for the DC2 6 Inch Dome that I mentioned above there is no magnification reported on the Ikelite site.

I hope someone will be so kind to help and suggest me what to grab, thank you with your advise, really appreciate it!

Hi Ivan

I'm sure someone will give you a much more detailed answer soon. But let me respond with a couple of quick thoughts:

Yep, you are not wrong, you need a wide-angle lens for pelagic and reefscapes. Actually the more fisheye, I would argue, the better.

Yep, you do need strobes. Ideally two. But you can start with one if cash flow is an understandable issue.

Wet lens and domes. I'm sure one of the Ikelite/RX100 gang will chip-in with detailed thoughts. The wet lens gives you that figure of x0.75 as it "distorts" the angle of view of the lens itself by, as you calculated, x0.75. So it makes your lens wider than it was by optical distortion. 

However a domeport actually creates a virtual image of what the lens can see - but much closer to the port than what the lens would normally register above water. So you are shooting the virtual image not the reality. The domeport does not magnify or reduce the field of view - it just creates this virtual image. So there is no magnification or reduction.

But what you do need is a lens that can focus closely enough to keep that virtual image sharp. On sensors the size of the RX and DX that's usually not a problem. But it becomes quite an issue if you move to full frame FX sensors. But that's a story for another day.....

Have fun with your new gear. Exciting!

PS: don't worry about feeling lost. We all do to start with. It's complex stuff . And there are no such things as stupid questions. It's the answers that can be stupid  

Hi,
my girlfriend used a RX100 mk I in a Recsea housing.
Bought her a Inon wide angle lens, and later a Inon fisheye lens:
http://www.inon.jp/products/lens/ufl165ad/top.html

Worked great.
Have upgraded her now to a Sony A5100, has a bigger and better sensor.

She used one strobe, but now she thinks about gettin a second one.....

Regrds,
Wolfgang

The domes you link are just that - domes they restore the same field of view you get on land so at the wide end the RX-100 will have the field of view of a 24mm equivalent lens which is 84° on the diagonal - this is wide but not that wide for underwater imaging.  There are a lot of wide wet lenses available, the most common ones will give you the field of view of 100° on the diagonal about equivalent to an 18mm lens - but they are specific to either 24 or 28mm lenses. 

So for example if you have the most common wet lenses setup for 28mm lenses, you need to zoom into 28mm to prevent vignetting.  A further complication is that if the compact has a long zoom and the port is a long way from the lens then you need to zoom in further still losing field of view to avoid vignetting.   You appear to have one of the earlier RX100 models with a 24-70mm equivalent lens - which is good they are relatively short and most wet lenses work fine with them and you don't lose a lot of field of view..

A couple of options - you could use the INON UWL-H100 for 100° field of view and also add the dome for optionally 144° field of view.  The dome is a dry dome and needs to be added on land see here for fitting a dome to a different wet lens: https://reefphoto.com/blogs/how-to/installing-the-dome-unit-on-inon-uwl-s100-zm80-wide-angle-lens.  This will give you two wide options with/without dome.  My understanding is these lenses are not zoom through and lose performance if you zoom in too much (go soft). 

For a zoom through lens you could look at either of the Nauticam WWL options - they give full zoom through.  The WWL-1 from 28mm  and the WWL-C from close to 24mm.  Giving field of view 130° at 28 and 24mm respectively.   the WWL-C would give to the equivalent to 10 to 30mm lens.  These are excellent optically but are big heavy expensive pieces of glass.  In theory you can remove them underwater - in practice what do you do with them when you take them off as they are so big and heavy?  You do need to take them off UW to burp them to remove air bubbles on the rear element and port glass.

Thanks Chris! I guess you are the same Chris who answered on my topic on scubaboard forum as well

please one last question for you, can you kindly check this Kraken Sports KRL-01? How do you rate it compared with the UWL-09 ? Karken lens look like is a 145 vs 130 and starts at 24mm instead of 28mm like UWL-09, do you see something else that i miss?  price are almost the same as UWL-09, is the 65 $ worth the Kraken?

Kraken Sports KRL-01 Wet Wide Angle Lens Review

Kraken Sports KRL-01 Wet Wide Angle Lens, 67mm
765 $

Fantasea AOI UWL-09F Wide Angle Lens
700$

Thanks!!!

No direct experience but two comments the Kraken weighs 1430 gr and the Fantasea 1033 gr in air - in in water weight for the Kraken is quite hefty - 640 gr.    If I was spending that sort of money I would seriously consider the Nauticam WWL-C it's 1050 gr in air and with the inbuilt flotation collar 250 gr UW.   It also has a glass front element - less prone to scratching.  It is more expensive, but Nauticam does have a great reputation for their wet optics.  It would be much better balanced on the little RX100 housing UW due to the flotation collar.

Depending on your housing and how far away the lens is from the port - the 28mm designed UWL lens is less likely to need to zoom and lose field of view to avoid vignetting, so you may not get the full wider field of the Kraken lens??  

There's lots of reviews of the Fantasea lens, but for the Kraken lens it's only retailers posting reviews.  Just google Fantasea UW-09F review and you'll get at least 3-4 non retailer reviews.