Underwater Bubble Blowin' Users Group

[Mark Thorpe]

Sharkguy,
I've had a few of the Ikelite meters crap out on me here, not mine but belonging to camera equipped divers etc. IMHO not very rugged and prone to failure.

Do you have an outlet for the Sekonics? I done a search a while back but could only find the odd one for private sale etc.

Learning Question: Seeing as the ASA value is accessible to the shooter wouldn't that then be set in accordance with the either the ambient / available light or to determine the 'look' of a required sequence?

What is the securing mechanism of your ACL housings port(s)? Shame its not bayonet to allow the SWP44 eh? I also have the Century HD .8 converter as I was also thinking of potentially using that. My mind may be on the right path after all.

I'll be interested to hear how your initial tests go.

Cheers,
Mark.

P.S I'm also looking to strap, clip, weld or bugger together some kind of color chart to one of my fins. I do have a WB slate on an articulated arm for my Z1 so I may take that idea and add a color slate to the reverse side. WB in 2k and less and Color Reference to boot.

[Ken Corben]

I still have my original sekonic L-164 with more than two decades of abuse still works. Picked up a newer one recently on ebay for $100.

I think it has been discontinued again so ebay and other UW photo communities might have some offerings.

Meter history/specs:
http://www.hydroflex.com/site/helphints/marine.html

Important tip: You'll need this nifty adapter to use batteries available today to maintain the "constant voltage" of the old lead batteries.

http://www.criscam.com/old/mr9.htm

[Ken Corben]

I won't get around to testing lenses until I can use a red camera. However, I did ask Evin Grant if he would be posting lens test results on the 17-35mm. It's on his to do list which is great.

I am very curious to see if the Century HD .8 will work on this lens with the 72-77mm ring adapter etc.

ASA
I read on another thread that ASA 320 with at least a 5 stop lattitude was the "imagined" red one 4k red raw setting. Sounds about right. Didn't specify frame rate but that's easy to adjust on the meter.

It's all coming back from my film days...WFO at night, F8-11 in green water and F11-16 in blue water.

BTW - the ACL housing is from the era of Flipper and the pioneers of UW filmmaking in those days, i.e, built like a nuclear submarine. No bayonet mount on dome port but it is a very nice piece of glass.

[Mark Thorpe]

ASA
I read on another thread that ASA 320 with at least a 5 stop lattitude was the "imagined" red one 4k red raw setting. Sounds about right. Didn't specify frame rate but that's easy to adjust on the meter.

Hey Sharkguy,
Wow, you speak mandarin too?? Great asset. OK, I'm Wiki'ing cinematography at the moment. Long words ............ my head hurts!!

Best,
Mark.
P.S WFO has something to do with Wide Open I take it. haha. Love to see the ACL housing, take a ride on it. I saw the attached image and was half expecting to see the Beatles peering out of one of its portholes.....lovely looking tub.

Wahhhhh, just realised what a dumbass I'd been with the posting regarding ASA values. Its amazing what one picks up in the other forums ........

[Ken Corben]

Found this US Navy report on evaluation of Kinoptic 9.8mm lens underwater thru a dome port.

Abstract : In the process of evaluating the overall performance of the wide-angle camera system used aboard the USNS Mizar (TAGOR-11) for underwater search, it was decided to investigate the imaging characteristics of the Kinoptic 9.8-mm lens used with the camera in order to isolate its limitations from those of the other components of the system. In use the lens is mounted behind a watertight, hemispherical glass dome. The water/glass, glass/air interfaces formed by the dome act as a negative lens, forming a virtual curved image of the (relatively) flat ocean bottom. This image in turn serves as the object for the camera lens. Tests were made of the len's ability to image both flat and curved objects in air, extending across its field of view. The tests show that the resolving power of the lens falls off greatly at the edge of the field of view for curved objects, so much so that only the general form of the resolution target can be distinguished. For both flat and curved objects, radial resolution is nearly twice as good as tangential resolution. (Author)

Original Link:
http://stinet.dtic.mil/oai/oai?&verb...fier=AD0722335

[Ken Corben]

OK,

I am not an optical/lens expert and have been spoiled by the Gates and Pace solutions for underwater to date. That said, there seems to be 2 solutions for Red underwater if you plan to shoot 4K Red Raw professionally.

Wait for the Gates system or design a custom system. I am choosing the latter only because I want to be shooting 4K Red Raw underwater this year.

My math and presumptions are solely based on what I've learned from this forum and are subject to error based on information/data provided.

No doubt one needs to use a corrected dome port on any lens they choose underwater since a flat port adds yet another focal length multiplication factor of x 1.339.

The Nikon 17-35 aligned with the dome port correctly yields the following FOV presuming the multiplication factors are correct for the mysterium sensor (The Mysterium’s capture area is 24.4 x 13.7mm 16:9 aspect ratio at 4.5K?):

35mm is 1.6 x 17 = 27mm or a FOV= 77 degrees
S35mm is 1.5 x 17 = 26mm or a FOV=80 degrees

Basically for us underwater guys this means the equivalent of the Nikkor 20mm at the 17mm end of the Nikon zoom...not bad for a $1200 zoom solution (see diagram 1).

Need wider? I will so I have explored the options. Firstly, there is already a shortage of 35mm primes and with the release of Red, well you know - I see Red users already driving up the price of the Nikon 17-35 on ebay. That said...

To obtain wide angle performance similar to the Nikonos 15mm lens in a prime configuration the choices are:

The $2k solution Nikon 14mm x 1.6 = 22.4mm or a FOV= 88 degrees
The $10K solution 10mm x 1.6 = 16mm or a FOV= 107 degrees
(see diagram for comparative FOV)

Then finally there is the question of using the Gates $5k SWP ports some of us already own. If the FOV of a 1/3" chip camera (Z1) behind this glass is 67mm at the wide end then:

1/3" = 67mm/7.5 = 9mm or a 10mm 35mm prime lens. (7.5 is the lens multiplier for 1/3" chip to 35mm equivalent). Again a $10K solution for a used 10mm prime.

The Red Zoom is an 18-85 so the wide end field of view underwater is 18 x 1.6 = 27mm or a FOV = 77 degrees.

Exhale...

[Ken Corben]

Here's a reliable source for sekonic spot meters...get 'em while they're hot.

http://stores.ebay.com/Underwater-Ph...QQftidZ2QQtZkm

or email queries direct:

joeswaney@earthling.net

[Ken Corben]

It nows seems apparent to me that "acceptable/applicable" professional underwater 4K will only be adequately accomplished with a Zeiss (or equivalent) 10mm ultra wide prime (excepting macro of course). In fact the focal length multiplying factor of red raw with a 35mm lens (x 1.5) benefits the macro shooter.

Obviously I will test the Nikkon 14mm vs the Zeiss 10mm to evaluate the differences but intuition tells me the 4K difference will be obvious. (Test procedure will be standard color chart/slates in daylight at f/11 4K red raw files scanned to 15 perf 70mm positives via redcode workflow to simulate underwater).

Currently, if one is a shooter for hire, the majority of clients will be happy with a 1080i output since the final cable tv broadcast pipeline compression is 5:1 (such as Discovery and hence the inability of S16 to hold up under this compression).

The realities of 4K stock footage vs "shooter for hire" are different animals in terms of the investment in glass and housing design.

A zeiss 10mm is $10K plus custom housing (>$20K) plus red raids, batteries, viewfinders etc = >$50K all in. This compared to a F900 UW system at >$150K is still an awesome breakthrough.

I like camdiver's original idea of interchangeable front ends. This would accommodate a Zeiss 10mm (4K red raw), a Nikon 17-35mm @2K (sensor windowing) and a macro set up.

The zeiss 10mm is in use underwater on Arri 435's. I'd say it's an 8" dome from the photo? Obviously barrrel and pincushion are correctable if hydroflex uses it.

[Mark Thorpe]

Way to go Sharkguy,
Great posts. Very good info here. Either way we look at it we are on the verge of parting with a lot of cash ......... :waaa:. Whether one shots for stock or as a shooter for hire we are still looking at custom front ends for the glass we will want to use. each shooter will be different. I imagine John at Gates will look at building the housing around the 18/85mm to get the product out there asap. From there on any additional lens options would have to have their own dedicated extension tube. I can see these getting expensive.

I for one will be selling pretty much everything I have equipment wise at the moment to make way for RED. That means a couple of camera systems and lots of basic accessories for the DV and HDV underwater shooter. I really like the Fathoms SWP44 but I am not sure if we're gonna be able to find a way to make it work. At least I'll be able to get a chunk of change for that to go toward whatever I see as my wide option. For the Macro option I'm continuing to look around.

Hey also thanks for the link to the folks with the Sekonic. Mailed them this morning with an order.

Cheers,
Mark.

[David Nardini]

Hello Mark / Sharky,

Concur with many of your ideas. Personally I've limited my search to 14mm (just picked up a reasonable Sigma 14mm/3.5 for £135 from eBay); performance seems good on a Canon 1D which is all I can test it on, marginally bigger chip size than the RED). Flare control is not ideal, but given the shape of the front element, not surprising (but can be controlled).

I agree that it would be nice to have Zeiss glass, but by the time you use domes, I do wonder how much of that great glass you are going to enjoy underwater (how close do they focus ? to avoid another +ve diopter lens being in the way).
If you can get your hands on a nice Hasseblad SWC housing with Ivanoff port (glass), then you may be doing some justice to the Zeiss, but these used to be matched to the 38mm Biogons (on the SWC). I really wish I still had mine to play / test with :bye2:

Mark, I still plan to try the SWP44 in front of a 17-35/2.8 Nikkor ... will report back as soon I can (assuming the folk in Bristol still have a unit for me to test against). Does the SWP44 perform fine on land ?

Achieving a good 90 degrees FOV (for 4K capture) with good edge definition with the RED is going to be challenging. IMHO there are few lenses which have achieved this to date underwater : the Nikonos 15mm and the SWC in a Hassy housing. Most other solutions have always been a compromise, especially dome optics. Sadly, the Nik 15mm will not be wide enough if one could be made to fit the RED (it's not really a 15mm, more like a 20mm).

Anybody out there who can make / polish up an Ivanoff port for us