BlackMagic Cinema Camera underwater custom housing

Dear All,

Sultan has received his BMCC EF mount and decided to take it downuder. After his Ninja2 house building experience, this time he as done a full fledged housing.

Offcourse the ports are borrowed from his existing housings.

Here are some specs:

> Housing is machained form aluminum cast;

> space to accomidate external battery;

> Follow focus is used to make focusing smoth and fast;

> Manul cotrols: Power on/off, Record, Iris (auto only), Focus;

> Flat port for Macro;

> Fathom 110 port (yes it works and wide enough to compensate for the 2.4 crop factor)

> Tested so far to 165ft by Sultan to check the behavior of the controls underpressure. We are sure it can go deeper

He has tested it with the Canon EF lenses: 16-35mm wide angle and 100mm macro.

Unfortunately, the waters here in summer we have bad visibility and does not help in the testing. Actually, it is like a sand storm down there - really bad.

I will be posting sample jpg images of the captured video later.

Here is an image of the housing with the Fathom lens:

There's some promise to this endeavor

I totally agree this looks like a really good solution to give a wider angle of view on they small sensor. Could a similar solution work with the pocket cinema camera with a smaller Fathom port.

Let's see the jps's Thani!

Hi there,

I am on a short trip - no a diving one unfortunately - and I hope these images make it through.

First a disclaimer : I am not aquatinted with Davinci Resolve nor I am good at color grading.

Simon, here are some compressed Sample for the wide angle fathom along with the 16-35 canon EF lens. The lens was sat at 16mm:

One more wide angle fathom along with the 16-35 canon EF lens. The lens was sat at 16mm:

Sample for Macro shots using the canon 100mm macro with a flat port:

Are they zoomed in or cropped?

Thanks Thani

Do you have a full HD still? These looked low res.

Congratulations for being one of the first to take this camera under water.

> Fathom 110 port (yes it works and wide enough to compensate for the 2.4 crop factor)

The Fathom is an excellent port. However, I do not quite understand how it "compensates" the crop factor. If the BMCC sensor has a 2.4 crop factor, wouldn't a Canon 16-35mm zoom be equivalent to 38-84mm? I might be wrong, but the sample pictures do not look ultra-wide (weitwinkel).

The hopefully-soon-to-be-released BM 4K production camera has a crop factor of about 1.7 and even that makes the Canon 16-35mm equivalent to 27-60mm.

I wonder would the EF-S series work with the BMCC under water. EF-S 10-22mm would provide a wider view angle.

http://forum.blackmagicdesign.com/viewtopic.php?f=2&t=3807

Jonny, non of the shots are cropped. Not the wide angle nor the macro ones. The lion fish in the fishing trap is a close up with the fathom port and the lens is at its widest 16mm.

Thanks Thani

 

Do you have a full HD still? These looked low res.

Yes, each is almost 2k more than allowed by the forum.

The Fathom is an excellent port. However, I do not quite understand how it "compensates" the crop factor. If the BMCC sensor has a 2.4 crop factor, wouldn't a Canon 16-35mm zoom be equivalent to 38-84mm? I might be wrong, but the sample pictures do not look ultra-wide (weitwinkel) (weitwinkel).

 

The Fathom was designed for the Sony EX1 which I think has a 35mm equivalent. This is why it looks like it is working at around 38mm. More testing needs to be done.

I am hopping the 4k will have some wide angle primes that will give us close to 12 to 16 mm. I will do some search ...

Here are some pictures of the housing that shows few controls the focus, record & auto iris.

The round long "view-finder like" is a good way to protect the screen from the ambient light. The screen looks clear and bright all the time. It works better than any shade I have used before. I wish it was square but this is what Sultan has in his reusable stock.

I would advise any manufacurer to avoid the standard shades that are closely attached to the back of the glass which is close to the screen. It is better to have the screen deep enough in the housing away from any light and have a small shade long enough to show the full screen

Another good idea is to avoid the standard housing design that follow the shape of the cam/lens. That would be okay for taking stills but not good for continuous video capture. A more stable rectangular shape would be preferred.

Thani, you and Sultan are pretty resourceful in your thinking. I love housings that are somewhat universal.

The EX1 is 31.4mm (35mm equiv) and has a lens diameter of 77mm (filter size). The 16-35 II (I assume you are using the II) has 82mm diameter. However, since the crop factor is 2.4, there's no vignetting with the SWP44C (or Fathom 110 in Sealux speak).

Why don't you try the 8-15 fisheye behind a dome port? That should give you about 19mm fisheye FOV, which should be around 130°, albeit barrel distorted. Or even the 8-16mm?

Why don't you try the 8-15 fisheye behind a dome port? That should give you about 19mm fisheye FOV, which should be around 130°, albeit barrel distorted. Or even the 8-16mm?

Where can we find dome ports that could fit the Sealux EX1 like housings with or without an adapter?

I have been looking at:

http://zenunderwater.com/products.php

But did not receive a positive reply from them yet.

Another selly question:

If you have a wide rectangular lens lets say 11 mm and place it in contact with a flat port - no gap - would you still get close to 11mm?

11mm rectilinear (i assume?) you will loose 25% of the angle (affect of water to flat glass - refraction)

110deg becomes 82 deg or there abouts

Thanks David.

Just to confirm, even if the lens is stuck on flat port?

yes. Inside the housing lens and flat port has no effect as both are in air. Stuck or unstuck. Flat port to water is where the 25% magnification occurs.

To keep the angle of the lens a dome that matches the lens optical property is needed.

Don't forget the crop factor, 11mm=26.4mm, then + flat port = 33mm or so. Go for the EFS 8-16 behind a dome port.

Also if you go much more than 60 degrees you will get issues with chromatic aberrations through a flat port.