39mp underwater

[Troy Aitken 0]

Good morning Loftus,

 

It has been awhile as I have been very busy. Thanks for the comments. I agree, in fact the dome port that was given to me by UK-Germany is an 8" dome port. The 28mm is huge. I don't understand why they did this. As I understand it now, there is a Super Dome port (9.5 or 10in) offered by Subal or Seacam. With some modifications would this not have been a better option? The corner to corner sharpness is perfect out of water and the software (Flexcolor) corrects any other related issues. Is there any info someone can send my way to get a better dome. By the way, I have the 1dsmk3 and I am very happy with it. Not ready to take it u/w though.

 

Thanks,

troy

[Troy Aitken 0]

Just got off the phone with Uwe at Uk-Germany and was told that they are building an acrylic 1meter cube pool to physically test for port corrections to correct the corner to corner issues. His estimate is around 6 weeks to have good results. This is good news for me and I will post more on the results with photos.

 

Thanks

troy

[loftus 42]

Good morning Loftus,

 

It has been awhile as I have been very busy. Thanks for the comments. I agree, in fact the dome port that was given to me by UK-Germany is an 8" dome port. The 28mm is huge. I don't understand why they did this. As I understand it now, there is a Super Dome port (9.5 or 10in) offered by Subal or Seacam. With some modifications would this not have been a better option? The corner to corner sharpness is perfect out of water and the software (Flexcolor) corrects any other related issues. Is there any info someone can send my way to get a better dome. By the way, I have the 1dsmk3 and I am very happy with it. Not ready to take it u/w though.

 

Thanks,

troy

I don't think there's a substitute for in water testing, so hopefully UK will work something out. I don't think you can be guaranteed better performance just because the dome is larger so probably you should see some tests, maybe with different diopters before buying anything. You may also want to contact Ryan at Reef photo, he is working on some custom domes.

Edited February 15, 2008 by loftus

[craig 0]

I was going to mention Ryan as well. He has a large dome in development and should be able to brainstorm an adapter.

[Troy Aitken 0]

Thanks guys,

According to Uwe, the size of the dome isn,t the problem. Rather it's the distance from glass to port. Since my 22mm equivilant w/a lens is not super wide maybe this is true, but the lens is huge. I don't know if this plays a factor in corner blur. I will contact Ryan at Reef. Thanks for the lead.

Troy

[Paul Kay 62]

Troy

 

Your problem is that you are using a simple, single element lens system (ie a concentric dome) in front of your sophisticated wide-angle lens. The use of a 'simple' lens system like this is bound to be the limiting factor.

 

Without wanting to go right into the 'basic' theory here, you will need to correctly position your lens in the dome as stated BUT given your high MPixel system and the probable lens quality, I'd suspect that image field curvature created by the dome will always be a problem. All the problems faced by smaller format dSLRs than yours will be magnified by a more exacting high resolution, larger format so you will probably find that repositioning your lens and port positions will help deal with some but not all problems.

 

There have been various methods tried to overcome wide-angle problems but in general it is accepted that beyond about a 90 degree field of view, image curvature is a limit on rectilinear wide-angle designs being used behind concentric dome ports. You are approaching this limit with an exacting system so you may well be optically constrained earlier (ie at lesser wide angles). The only solution is to use fisheye lenses or get someone to design a non-concentric dome port specifically for your lens (could be an exceedingly expensive option). I've also wondered if perhaps an aspheric diopter might be a solution but found nobody able to supply anything (something like a varifocal spectacle lens?!).

[Troy Aitken 0]

Uwe is buliding a small testing pool. So lets see what he comes up with. Any improvemnet in corner sharpness will be greately appreciated.

troy

[Tom_Kline 141]

I spoke with a housing designer about housing a 40mm Distagon (retrofocus lens design) Hasselblad lens a number of years ago. This lens has an 88 degree (diagonal) angle of view on the 2 1/4 inch square format. My recollection is that he said it would require a 10 inch dome port. The Superwides (38mm non-retrofocus design, 90 degrees) did OK with 8 inch dome ports.

[Paul Kay 62]

Dome size (diameter) and lens field of view/focal length are NOT fundamentally related!

 

The dome diameter dictates the distance of the curved virtual image it creates from the dome.

 

The idea of a diopter is to allow a lens to focus on the centre of the curved virtual image (of a subject at infinity) when the lens in use is physically adjusted so that it is also focused at infinity - ie it retains the full focus of the lens in use. The diopter used is in this first instance dictated by the dome diameter, although strength may be varied depending on the close focus ability of the lens in use. Some lenses may not even appear to need a diopter as they can focus close enough to focus on the virtual image, but for other optical reasons they may be beneficial.

 

The problem with subjects which have depth to them (ie close corner detail) is that the close corner subject matter may lie at the corner of a cuved virtual image very close to the port indeed (from the camera's viewpoint) and this point lies so close to the lens that it is not possible to retain its 'virtual' position in focus by stopping down. That is to say, there is insufficient depth of field to enable the required 'thickness' of the curved virtual imagery to be all in focus. This is the basic problem with using concentric dome ports!

 

Solutions include accurate alignment of dome port and lens, use of appropriate diopter, using as small an aperture as possible and last but not least, choice of subject matter which exhibits the problem least (ie minimise close corner detail).

 

However the limit for which 'good' correction is possible is accepted as being a 90 degree field of view, and with more demanding systems (such as digital MF or hi MP dSLRs) this is likely to reduce.

 

Sorry to labour this point, but you need to have a good understanding of the optical problems associated with dome ports when aligning/optimising lens/diopter/port combinations. In general, a larger port backs off the virtual image which is often helpful but limits close focus ability (where abberations due to using a simple lens system, will kick in as you get too close). Dome ports are a compromise!

 

Tom on your comment, the Biogon 38mm is now a very old lens indeed (a 50s design I believe) and whilst it was housed, I suspect that in film days the resulting images were adequate rather than startling. Troy's system is likely to be far more demanding.

[Tom_Kline 141]

Dome size (diameter) and lens field of view/focal length are NOT fundamentally related!

 

The dome diameter dictates the distance of the curved virtual image it creates from the dome.

 

The idea of a diopter is to allow a lens to focus on the centre of the curved virtual image (of a subject at infinity) when the lens in use is physically adjusted so that it is also focused at infinity - ie it retains the full focus of the lens in use. The diopter used is in this first instance dictated by the dome diameter, although strength may be varied depending on the close focus ability of the lens in use. Some lenses may not even appear to need a diopter as they can focus close enough to focus on the virtual image, but for other optical reasons they may be beneficial.

 

The problem with subjects which have depth to them (ie close corner detail) is that the close corner subject matter may lie at the corner of a cuved virtual image very close to the port indeed (from the camera's viewpoint) and this point lies so close to the lens that it is not possible to retain its 'virtual' position in focus by stopping down. That is to say, there is insufficient depth of field to enable the required 'thickness' of the curved virtual imagery to be all in focus. This is the basic problem with using concentric dome ports!

 

Solutions include accurate alignment of dome port and lens, use of appropriate diopter, using as small an aperture as possible and last but not least, choice of subject matter which exhibits the problem least (ie minimise close corner detail).

 

However the limit for which 'good' correction is possible is accepted as being a 90 degree field of view, and with more demanding systems (such as digital MF or hi MP dSLRs) this is likely to reduce.

 

Sorry to labour this point, but you need to have a good understanding of the optical problems associated with dome ports when aligning/optimising lens/diopter/port combinations. In general, a larger port backs off the virtual image which is often helpful but limits close focus ability (where abberations due to using a simple lens system, will kick in as you get too close). Dome ports are a compromise!

 

Tom on your comment, the Biogon 38mm is now a very old lens indeed (a 50s design I believe) and whilst it was housed, I suspect that in film days the resulting images were adequate rather than startling. Troy's system is likely to be far more demanding.

 

Although more than 50 years old, the Biogon lens is one of the best wide-angles ever designed. It is unrivaled by most current lenses. The main improvement was the application of multicoating, which has only been around since about the 70's. There are Biogons still being made including some of the sharpest lenses in Leica M mount. The current 21mm f/4.5 has a design that is very similar to the 38. One reason for the 38’s reputation is that it is a non-retrofocus design. This may have influenced being able to adapt it to UW use, see my last question.

 

The point of dome diameter: A dome of a given diameter will project a virtual image that is independent of the camera lens, etc. However, I assume a larger diameter done will project a virtual image that is has a 'larger radius of curvature' than a smaller one. For example, when a given lens is focused on the middle part of the virtual image (on the optical axis, the very center that is parallel with the plane of focus), the periphery is focused further away than the center. This is easily seen in some fisheye shots: focused on a subject in the middle and the background near the edge of the frame is in focus, but background in the center of the frame is not. How does the shift to farther focus within the field (as angle from the optical axis) change with dome size? What is poorly described in the literature is the shape of virtual image – it is only spherical at certain distances, aspherical at others. That is why I put larger radius of curvature in parentheses above.

 

BTW, Does the position (does the size appear larger or smaller) of the entrance pupil of a retrofocus lens change with angle as measured from the optical axis? Is this at the core of the issue with this Troy’s lens? Symmetrical lenses like the Biogon may not have this issue.

[Alex_Mustard 0]

Although to use it underwater Hasselblad commissioned Zeiss to design and make a Ivanoff corrector port and dioptre to make the best use of the Biogon 38mm lens underwater. Rather than a dome.

 

Although I have never tested it (I do own the Ivanoff, dioptre and Biogon 38mm on a SWC), my suspicions are in agreement with Paul that the Biogon would not measure up against most modern lenses. The instant review of digital has made us incredibly demanding about corner sharpness - in a way that we weren't 10 years ago.

 

Alex

[Paul Kay 62]

Hi Tom/Alex

 

Tom, I'm not absolutely certain that I follow your comments but I'd suggest that my quoted discussion does assume an awful lot and is 'true' only with many assumptions made (ie its an overview of the simplistic theory). As subject matter becomes closer, a whole lot of discrepancies will certainly start to appear, most of which will add to image degredation. The whole point of my explanation is to show that whlst empirical testing will establish an optimised system, no amount of adjustment and testing can get around the deficiencies of a simple concentric dome port in front of a lens approaching 90 degree field of view. At some point a sensor and lens combination will have its corner performance limited by any dome port and I'd say Troy is probably using a system which will be so limited, as will most hires dSLRs and ultra wides - this is now the holy grail of underwater photography and will probably require innovative design to deal with.

 

On the comment about the Biogon design, I have no doubt that it is good (I've owned a couple myself) but manufacturers are now having to redesign and optimise lenses for digital. There are some interesting explanations of the abilities of Leica M lenses on digital but even these most beautifully designed, hand assembled pieces of glass have problems with digital (one of mine is in Germany being recallibrated for digital at the moment!). None-retrofocus designs w/a designs may cause s many problems as they solve (the M sensor uses angled micro lenses to solve some of them and the camera uses some form of image processing too).

 

Alex, I met someone camping out in the bush recently, miles from anywhere - tent, compressor, generator and diving gear plus Hasselbld housing!

[Tom_Kline 141]

Although to use it underwater Hasselblad commissioned Zeiss to design and make a Ivanoff corrector port and dioptre to make the best use of the Biogon 38mm lens underwater. Rather than a dome.

 

Although I have never tested it (I do own the Ivanoff, dioptre and Biogon 38mm on a SWC), my suspicions are in agreement with Paul that the Biogon would not measure up against most modern lenses. The instant review of digital has made us incredibly demanding about corner sharpness - in a way that we weren't 10 years ago.

 

Alex

 

 

The Petersen-Gates H38 housing uses a dome port. Without a proper digital sensor for the superwides we will never know. 'Proper' might entail some of what Leica has employed in the M8. Rumors are that a FF M8 sensor may be on its way so there may be a new solution the using short BF lenses.

Tom

 

Hi Tom/Alex

 

Tom, I'm not absolutely certain that I follow your comments but I'd suggest that my quoted discussion does assume an awful lot and is 'true' only with many assumptions made (ie its an overview of the simplistic theory). As subject matter becomes closer, a whole lot of discrepancies will certainly start to appear, most of which will add to image degredation. The whole point of my explanation is to show that whlst empirical testing will establish an optimised system, no amount of adjustment and testing can get around the deficiencies of a simple concentric dome port in front of a lens approaching 90 degree field of view. At some point a sensor and lens combination will have its corner performance limited by any dome port and I'd say Troy is probably using a system which will be so limited, as will most hires dSLRs and ultra wides - this is now the holy grail of underwater photography and will probably require innovative design to deal with.

 

On the comment about the Biogon design, I have no doubt that it is good (I've owned a couple myself) but manufacturers are now having to redesign and optimise lenses for digital. There are some interesting explanations of the abilities of Leica M lenses on digital but even these most beautifully designed, hand assembled pieces of glass have problems with digital (one of mine is in Germany being recallibrated for digital at the moment!). None-retrofocus designs w/a designs may cause s many problems as they solve (the M sensor uses angled micro lenses to solve some of them and the camera uses some form of image processing too).

 

Alex, I met someone camping out in the bush recently, miles from anywhere - tent, compressor, generator and diving gear plus Hasselbld housing!

 

Think water-contact optics (re. Nikonos RS).

What sort of calibration? Even with film the real fast Leica lenses (such as Noctilux f/1.0) had to be calibrated to specific bodies because the tolerances are so low.

Tom

[craig 0]

All ports are "water contact optics". Video systems use solutions more elaborate that dome and flat ports as a matter or routine. They have to although their resolution requirements, until recently, aren't nearly what still cameras have.

[Tom_Kline 141]

What is meant by the jargon 'water contact optics' or more specifically a 'water contact lens' is a lens designed from the ground up to be used in water. It is not suitable to use such a lens in air. Adapting an air lens to be used UW is not the same thing. The Nikonos lenses with the W and RW designation are water contact lenses. The 50mm lens for the RS works (one can form an image in the film plane) out of water (I have done this) but is not as sharp as UW, the corners are soft.

Tom

[craig 0]

I understand, but the term used was not descriptive in any way. The questions regarding such an design are whether it is designed as a supplementary lens (as it is with video systems) or whether it is the entire optical system. If it is supplementary, how difficult will it be to get good performance and with what primary lenses will it be designed to work. If it the other approach, i.e. like the RS, then what will the housing system be that uses it. In either case, what will the business case be that can justify it. Nikon did it but got out of that market.

 

I believe that we will reach the point, if we haven't already, that we will need these kinds of solutions to make further meaningful improvements in IQ both for wide angle AND macro. Flat ports introduce noticeable CA and it IS possible to solve that problem. I'm disappointed that manufacturers haven't made any attempts at achromatic macro ports, but then some don't even do a good manual focus port.

 

You know, if it's a supplementary lens, it can be designed to provide 90+ degrees with 35 mm equivalent lens. That's how it's done with video. With video, they even provide full 10x zoom-through.

[Paul Kay 62]

Tom

 

My M75/2 was simply not focussing on the image sensor plane - not far out but enough. It was probably fine on film though!

 

I take your point - in fact Leitz Canada built some genuine in water lenses - under the name Elcan - which I think may have been for the US Military - they are now collectable and very expensive as are the few housings built around them.

 

Craig's point is very valid, and say that systems such as Troys and the latest hires dSLRs will probably make optical demands which exceed the optical performance which can be delivered by the existing type of underwater optics that we are currently using. My own personal opinion is that the most likely/viable/cost effective route forward would be to get an aspheric (non-concentric or elliptical) dome designed and built. To do so would I expect mean that it would have to be matched to a specific lens (such as Troy's 28) or focal length (perhaps 14mm on FF) and would be optimised for a specific distance (say 1m) with performance drops either side of this. This would of course be an expensive undertaking and would need custom mounts for different housings. This is possible and I have briefly looked into the idea but the optical design is the expensive bit (10s of £1000s) as moulded aspheric lenses are far from unknown today, but I am unsure if it is as yet cost effective as I doubt that sufficient people would buy such a lens.

[ColinMunro 0]

Somewhere I've read that Titanium doesn't like high pressure oxygen (perhaps it becomes slightly reactive) but I'm not sure if there is any substance in this. Can anyone confirm or deny? (It does seem odd that Titanium isn't used more in housings as it should be an excellent material unless it has a drawback other than cost/machining).

 

Hi Paul.

 

This may be what you're thinking of.

 

'I am a metallurgist who has worked for 16 years in the titanium industry. I would not use titanium with 100% oxygen at any pressure. The danger of a catastrophic accident (ie: rapid oxidation or even explosion) is just to great to risk it.

 

Steve'

 

from http://www.titaniumservices.com/wwwboard/messages/575.htm

 

Colin

[buddy 7]

I was reading this thread and controversy with great interests and just wonder why not even 1 pictures of the actual camera, housing and flashguns have been uploaded (or did I miss this?). I would like to see a few of them (and it does not have to be in 39 MP quality!). So Troy, can you show your rig?

 

And furthermore, I do not believe that one single commercially paid uw job paid off a $50k investment. Dreaming? like to hear more details on that too.

[Troy Aitken 0]

Hello Buddy,

 

The H1 Digital 22mp was paid for by one job when it was loaned to me by my supplier, long before what I have now with my housing. hope this clears it up.

 

Also your right, I will post some photos of my set up as soon as I get back from assignment here in Long Island.

 

Troy

Edited February 22, 2008 by Troy Aitken

[chriscrumley 1]

Troy,

 

I've been looking at the UK-Germany housing and have wondered if it works. Sounds like you're the man to answer the questions; I haven't been successful at getting much info from Germany.

 

Are you primarily a macro shooter?

 

Sounds like you're using or going to use the 28mm on the H3D for wide angle and not the 35mm. Have you done it yet? How are the edges and corners? What is the wide port? Acrylic/glass? 8 or 9 inches. Are there spacers for the port to get the entrance pupil distance right?

 

Is heat buildup from the back any issue?

 

I use an H2/39CFH for most of my advertising work (dry) and a Seacam MkII for wet work.

 

I tried to get Hasselblad to fund a UK-Germany housing for the H2 in one of their on-going assistance programs, but they weren't in the mood.

 

I'd have a Seacam MkIII housing if they weren't so damn expensive. The exchange rate is killing purchases that need to be based at least somewhat on ROI.

 

Even so, I'll be very interested in anything you'll share. And, p-l-e-a-s-e be careful with your o-rings.

 

Chris Crumley

http://chriscrumley.com http://blog.chriscrumley.com http://blog.chriscrumley.com/BlogBook Etc.

[chriscrumley 1]

Buddy,

 

I've had multiple single-image US$50k plus sales, so that kind of ad job is certainly doable.

 

It sure isn't everyday stuff for most of us, but it certainly is believable.

 

Chris

[pmooney 6]

Troy,

 

I'd have a Seacam MkIII housing if they weren't so damn expensive. The exchange rate is killing purchases that need to be based at least somewhat on ROI.

 

Chris Crumley

http://chriscrumley.com http://blog.chriscrumley.com http://blog.chriscrumley.com/BlogBook Etc.

 

If housing a 1DsMK111 is your goal then the new Aquatica unit is an affordable option. Combine it with their Glass Megadome and your all set - 21MP here you come.

Edited May 20, 2008 by pmooney

[chriscrumley 1]

If housing a 1DsMK111 is your goal then the new Aquatica unit is an affordable option. Combine it with their Glass Megadome and your all set - 21MP here you come.

 

pmooney,

 

That's really a strange name.

 

I have an Aquatica A67 and had a raft of Nikon film 35mm Aquaticas, so I'm very comfortable with Aquatica and I am considering one for the MkIII.

 

There is no free lunch, however. The S45 finder that swivels on the Seacam makes head-dry under/overs easier than most other finders.

 

That, and I have a ton of Seacam parts and pieces that might have to be replaced with Aquatica similars. Glass domes, wide dome, macro, port extensions, gears, finders, etc.

 

I use the MkIII and Hasselblad dry and my only MkII use is the housed one. I'll have to live with that for awhile.... until I bite the bullet for either the Aquatica or Seacam MkIII.

 

Chris

[pmooney 6]

pmooney,

 

That's really a strange name.

 

Its not very strange when it's signed on the bottom of your check.

 

There is no free lunch, however. The S45 finder that swivels on the Seacam makes head-dry under/overs easier than most other finders.

 

That, and I have a ton of Seacam parts and pieces that might have to be replaced with Aquatica similars. Glass domes, wide dome, macro, port extensions, gears, finders, etc.

 

I guess that means you will need a Seacam port to Aquatica Housing Conversion ring.

 

 

 

Peter

Edited May 20, 2008 by pmooney