Deep Wreck Project - lens-port combo?

I have a wreck project coming up which will need a rethink to do safely. The wreck lies in 148m on the sand, deck at ~140. I use a Canon 5D2 in an Aquatica housing, 14mm lens and 8" port. Clearly this rig is not rated to this depth. However I have shot previous wrecks at 135m with a Nexus housing and minidome without any problems, and I regularly take housings well past their rated depth without issues. However this is stretching things even for my level of risk acceptance.

So I am thinking the Aquatica minidome might be the best choice for me given its hemisherical shape and small volume which I would expect to have a greater pressure tolerance.

So my question is, what is the best lens for the job behind this port? Sigma 15mm fisheye? Tokina 10-17mm?

Can anyone tell me if they are satisfied with these lens/port combos and whether an extension ring is required?

And out of interest, anyone care to share their deepest dive with Aquatica gear so make me feel less nervous? :-)

Cheers

Harry

Oh and BTW, if I go with the minidome and Sigma 15mm, I gather I have to cut the shade off the lens. How do you do that safely?? :-o

Hi Harry, IWe can't honestly recommend that you go beyond the recommended depth rating of the housing.

However, should you want to proceed, I would certainly try and find a pressure tank and subject the housing and dome (without camera inside) to the pressure equivalent for an hour at least. Plan B would be to attach the housing to a weighted line and lower it at the actual dive site without a camera inside, .

you will need to cut the shade of the Sigma 15mm partly, that would be best done by a camera repair facility. its not something you want to hack off blindly.

Hi Jean, thanks for your comments. I certainly would not expect Aquatica to endorse this madness, and clearly this is done entirely at my own risk!

However I am interested whether you agree that the 4" hemispheric glass port should have a theoretical higher pressure tolerance than the larger acrylic domes, which I believe have been known to pancake or invert at depth?

With the lens shade shaved, this port is optically acceptably matched with the Sigma 15mm?

Thanks

Harry

I always thought its not the housings that are 'depth rated' - but the springs on the buttons? Too much pressure and the tension on the buttons becomes too great - so causing them to press in - so causing the camera to malfunction?

Hi Richard, that is certainly the case. The buttons are the first thing to become unworkable at excess depth. Often they are OK until you depress them, then you find they are stuck down so that function is permanently active or disabled. So I have found that as long as the camera is set up and you only use the shutter release and rotary controls all is well. But I usually forget and press the review button or similar then all is lost!

I expect that the housing and dome will be ok for this dive, but naturally I am a bit nervous about it!

I have used Subal and Nexus housings at well past their rated depth. I know of several guys like Leigh Bishop who take the Aquaticas past 120-130m. I just dont have any experience in the 140-150m range with these cameras. I have even dived the GoPro in its little plastic housing to 127m and only had button issues.

Golem Gear make a lovely 300m GoPro housing which we have taken well past 200m on cave dives without problems. They must have strong button springs.

Hi Jean, thanks for your comments. I certainly would not expect Aquatica to endorse this madness, and clearly this is done entirely at my own risk!

 

However I am interested whether you agree that the 4" hemispheric glass port should have a theoretical higher pressure tolerance than the larger acrylic domes, which I believe have been known to pancake or invert at depth?

 

With the lens shade shaved, this port is optically acceptably matched with the Sigma 15mm?

 

Thanks

Harry

Well the 4'' does have a small radius which is in this case does work for you, on the other hand, I have yet to see an acrylic dome invert itself, be it a 6'' or an 8" !!!

Such a small dome on a full frame camera will be a tough one, typically small dome are designed for shooting up close, with a cropped sensor (shorter focal length and smaller image circle) at the minimum distance with the smallest of aperture, you will be shooting a wreck at some distance on a full frame at close to, if not, full open aperture. you will be seriously out of the comfort zone of this dome design Harry.

Thanks Jean, I hear what you are saying about the lens-port combo in this application. Hopefully with the 32000 lumens of video light and a high ISO I will get some useable images and video at >f8. Not sure what else to do to be honest.

Maybe I just risk the 8" acrylic port if the 4" is not producing sufficient image quality.

Any way I have bought the Sigma 15mm and my supplier is ordering the minidome. I will report back to this thread on the results (or disaster!)

Appreciate your input.

Harry

Harry,

I've had the aquatica 6" dome to 140m, seemingly no ill effects.

The 6" dome gave me a good size compromise on crop sensor, though after moving to full frame I typically got blurred edges past f/8-10.

Given the dive at hand, is be happy to take that image qualify hit to reduce size of rig.

I never tried the 4" dome due to suggested quality issues with full frame.

Another side effect of the smaller domes was the weight of the housing rig. I found this quite a serious issue, and adding your lights to it will only compound this.

I'm now using the nauticam carbon fibre float arms, they're at least good to 125m based on my tests without compression. Two 12" unit provide some serious lift too, so should address the negativity.

Ds

Sent from my iPhone using Tapatalk

Good point about the weighting. The whole rig will be on a scooter so I need to do some pool testing ASAP.