Wednesday, December 31, 2008

A different level of impact

Loose thoughts by Bjorn Landfeldt

After the government released its report on Internet content filtering senator Conroy released a statement that the government will test P2P filtering as such tools currently exist. This is very interesting because the bar is raised considerably if this is the case.

In the report I did not raise and strong concerns with performance degradation at the ISP level when comparing HTTP requests to a blacklist. I believe the performance penalty can be significantly reduced by purchasing additional equipment and the ISPs can be compensated for such roll out. The current trials can actually answer some of the questions as to the performance penalty and cost to alleviate them in terms of additional equipment purchases.

However, with P2P filtering the situation is very different. In this case, the filtering system has to do deep packet inspection to figure out if something should be banned or not and this is very different to checking terminating address. The deep packet inspection will be used to try to identify what kind of content is accessed since in a P2P content distribution network end addresses are useless. This puts us in the realm of dynamic filtering which pretty much is the worst nightmare for the Australian ISP industry and necessarily will mean significant performance penalties for the Australian public. Even if some video in a bit torrent would be called "child abuse that is illegal in Australia and should be filtered by the government" a filter would have to perform analysis of this text to determine if the media should be filtered. Changing the name of this file to "daisies in summer" and the filtering system would have to analyse the content of the video itself to determine if it is illegal and should be blocked.

In addition to performance penalties, such system raises much stronger privacy concerns. Even if very little content would actually be blocked with such system, someone is really checking how Australian citizens are using their network connections.

It will be interesting to see how this will pan out.

Thursday, December 25, 2008

It is a shame

Loose thoughts by Bjorn Landfeldt

Over the past couple of days there has been lots of articles and blog posts about Internet content filtering in Australia. Sine I am involved in this debate I have spent quite some time to go through the posts to see what interesting thoughts and views are out there.

I am a bit surprised at the emotional charge this issue has and really think it is a shame that the public debate is overshadowed by a sea of emotional outbursts and wild accusations. Especially, I think it is a shame that Senator Conroy's blog is flooded with such content, that is where people should try to be taken seriously.

I think it is absurd to compare the Rudd government with the Iranian or Chinese governments. I am also surprised that senator Conroy actually bothered to meat that criticism.

I am equally amazed at the notion that if you appose this scheme in any way you support child molestation.

It is becoming clear to me why this issue became such a prominent political issue in the latest election campaign and why it is so important to win political ground. It is a shame.

I am a proud Australian since 2007 but I was born and raised in Sweden. For all the lobby groups that are seriously concerned with children's welfare, I urge you to have a look at a country that is running at a few parsec higher speed than we currently are. I live in Sydney's South-West, in a suburb that had a plane crash, two shootings and a siege resulting in 4 dead all during last week. There is a lot of child neglect and abuse going on out here and this is something to really get upset about.

Of course, really caring for our children means a hefty tax bill......

Nothing is that easy, it is a shame.

Tuesday, December 23, 2008

Internet content filtering

Loose thoughts by Bjorn Landfeldt

There was an article in the Sydney Morning Herald this morning regarding a report I was involved in preparing for the Australian government late last year. The study was concerned with the feasibility of filtering content on the WWW at the ISP level. My own contribution to the report was not the major part and I mainly carried out a limited technical study

I feel that it is necessary to make a few things a bit more clear concerning the news paper article.

First, I don't think the study was very secret. In fact, the study made a wide consultation with the Australian ISP industry, content providers and other organisations / stake holders. There has been wide spread knowledge of this study even though the findings have not yet been widely released as far as I understand after reading the article. It is not my place to comment on at which time the government releases its reports even though I see no real reason not to release this specific report.

The issues raised in the report have largely been covered in preceding reports, at least the sections I was providing input to and even though they are very important issues to consider, I don't think they are damning since the issues are well known.

My stand on this issue is that there is a need to increase the scale of investigations if any such scheme should be made mandatory. If such a scheme is voluntary many of the difficult issues become obsolete or at least manageable. The following opinion merely reflects publicly available information that is not limited to the report. Anyone can search for this information in their local library or on the world wide web.

So, what is the big issue as I see it? A blacklist requires manual effort in order to determine what should be included. The Internet is a network of networked computers that carry information in many forms and realms, one of which is the World Wide Web. If we restrict ourselves to talk about only WWW, we have a global network with billions of pages worth of information. The information is made up of all different languages of the world and incredible diverse. Some information has a very high profile and some information has very limited visibility. Since a blacklist would rely on user reporting, it is questionable how efficient it would be to locate unwanted content in the first place. Second, every case would have to be tried to see if it breaches Australian law and falls within the categories specified for the filtering list. It will be a very difficult task to do this for content in the grey zone in all different languages. If the point is to stop child pornography, determining if a model is 19 or 25 in content from a different country with different jurisdiction is not an easy task and would be quite labour intensive. The next question is who is responsible for blocking of material that is legal if the wrong judgement is made?

The only way to identify such material quickly and significantly limit the risk of accidental access is to do some form of dynamic content filtering. However, the state of the art of such technologies is very limited in accuracy and if they are to be used there is a consequential performance impact on the response times of systems or at least an increased cost for the service provider. Current filters are rather good at detecting certain patterns of information such as a combination of many images and certain keywords usually means a porn site. However, there are at least two additional dimensions to consider. First, the current filters only look at such patterns, they do not try to analyse the actual content in any meaningful way. It is therefore difficult to distinguish between different types of content where there are similarities. For example, if a web site contains information about sex education or erotic content. Second, more and more content moves to other forms of multimedia and filtering and detecting the nature of content is much much harder in this case. For example, analysing a video and detecting that it has adult content is not a lightweight computational task. Separating sex education from porn is even harder. Third, if indeed there would be widespread filtering of content the providers would see a need to obfuscate content to fool filters. When we step into this realm it becomes very difficult for any filters to keep up.

This discussion can then be applied to an environment with other addressing realms than the WWW such as P2P networks and social networking applications and realms which shows that the level of difficulty is very high indeed. There is also a strong movement to anonymise users on the Internet to counteract information logging. Using simple tools such as VPNs to cross the Australian border would also enable circumvention of any centralised filtering scheme.

I believe it is a shame that the issue became a political issue in the latest election campaign. The question of protecting us from certain content is important and there should be a healthy and public debate about it. I have no knowledge of what other steps the government is currently taking to investigate this matter but I hope the scope of investigation is much broader than only doing a performance study of blacklist filtering.

I tried to download one of the free netalert filters for the computer my oldest daughter is using a while ago but the provider web site seems to be down. It is a shame, because I don't want her to see many things out there at her age, but I am making that choice and I accept responsibility for the over blocking.

Bjorn Landfeldt

Wednesday, November 19, 2008

Epoque DCL20 Wide angle lens review

Loose thoughts by Bjorn Landfeldt

So, I bought an Epoque DCL20 wide angle lens in New York a week back and had the opportunity to take it for a dive last weekend. Before I bought it, I could find no information about its performance on the web so it was a bit of a gamble whether to buy or not.

These are my initial thoughts without having had much time to really conduct experiments.

The lens is not very big, it doesn't really add much to my Ikelite and strobe arm setup for my G7, it adds a few hundred grams but that's pretty much it. The thread is so large and well defined it is easy to screw the lens on the port under water, I don't think there is much risk of damaging the thread with clumsy thick gloves etc.

The lens magnifies about 0.56 x so the angle is quite wide. My G7 has a 35mm equivalent of a 35 mm lens so I get about 19mm focal length (in 35 mm) with the Epoque attached. This is wide enough for the Ikelite standard port to get in the way and the result is vignetting (probably lots). I therefore also purchased the replacement port from Ikelite which is about 10mm shorter than the original port. There is a small limitation in the amount of zooming in one can do with this port because the lens eventually hits the port, but this is beyond the zoom when one can still focus in macro mode so I can't imagine it would be missed by anyone.

Above water one gets a bit of a shock when attaching the lens and taking a shot.

The first photo was taken without the Epoque at 35 mm (equiv.) and the second photo was taken at the same setting with the Epoque mounted. There were a couple of things I noticed straight away that worried me quite a lot.

First, there is obviously the barrel distortion to take into account. I was wondering what this would look like when taking photos under water. Second, there is significant softness around the edges (actually gradient from fairly much the center). Third, there is still a bit of vignetting happening. One obvious thing I noticed was the fact that the Ikelite housing has a pretty shoddy make. The camera is not centred in the lens barrel and when I first got the housing I had to cut of a lot of the light masking foam around the lens. With the Epoque mounted I get big black vignetting parts on the left side of the barrel and nothing on the right side. I lose quite a bit here since it means I have to crop much more to get rid of the vignetting.

So what happens under water?

I am pleased to say that my concerns are largely invalid when the lens comes in the water. First, I wanted to see what the coverage would be and how much distortion there would be so I took a few maximum wide angle photos of different things.

The visibility of the day was not too bad, probably about 8 or so meter (~24 ft) but there was a lot of particles in the water. The first photo would have been taken at about 3m from Taso and one can see that there is a lot of coverage at that distance and the diver is well defined since the distance is quite short.

Also, there is little evident barrel distortion in the photo. I then took some photos at closer distance and also tried to take some close up with the Epoque still attached. There was little evident distortion even at closer distances but closeups were heavily affected by the wet lens.

In the closeup of the snail one can clearly see how much blurring there is of the photo surrounding the snail. It doesn't look too bad in this specific photo, but it canreally make things bad.

So, all in all, I am looking forward to playing around much more with the lens and get a better understanding of what it can do and where there are limitations.

Saturday, November 8, 2008

Automatic BCD???

Loose thoughts by Bjorn Landfeldt

A pair of undergrad students presented the outcomes of their thesis work on an automatic BCD in early October at the UNiversity of Auckland (Mechatronics).

The (invention) is a control system for managing ascents and descents of divers using an embedded system and a control loop for the inflation circuit. Apparently, there is also what is known as a cruise control whereby the (pilot) sets desired depth and the circuitry maintains that depth.

To me this sounds like a pretty stupid idea for a number of different reasons such as:

1) Increased reliance on equipment, especially for new divers who might be in a very bad position if the circuitry fails
2) One more point of failure (actually several)
3) Need to bring batteries for the BCD on a dive trip (or do you hook it up to 240V and charge overnight?)
4)Costly circuitry and mechanical control components
5)Completely unnecessary, buoyancy is a necessary skill to learn anyway and it needs to be practiced

I wonder what George Irvine III would say? Unnecessary Crap perhaps!

Leisurepro shop

Loose thoughts by Bjorn Landfeldt

So, I finally got to go to New York and visited Leisurepro's shop. It is tucked away on top of ADORAMA photography run by the same owners. After one has been shopping for dive gear on their web site for a while, and experienced the massive range of gear they carry, the shop is somewhat of an anti-climax. I fully understand that real estate on mid - lower Manhattan is pretty expensive contrary to the impression Macy's gives. But, the 40 or so sqare meters of Leisurepro shopping experience is pretty dismal. In the shop itself there is nothing to look at apart from a handfull of items so one has to be prepared when going there. The idea is to shop on the web first, and print out a list of items to look at. Presenting the list to the staff and the stuff comes up from the basement if it is in stock. Then you can see the things you are interested in up close.

So, what's the verdict?

Leisurepro serves a purpose, cheap prices for gear when one knows what to get. However, the shopping experience is far from satisfactory, if one wants some advice or just to browse this is not the place, there are many dive shops that do a much better job at this. I guess you can't have everything.

Tuesday, October 21, 2008

New world record

Loose thoughts by Bjorn Landfeldt

Yesterday, the current free diving world champion, Tom Sietas broke the world record for holding ones breath voluntary. He managed to break the previous record of 17 minutes and 4 seconds, bettering it to 17 minutes and 19 seconds during a TV show "Live with Regis and Kelly".

What the....

I wonder if that makes any permanent damage to the brain? How much pain is involved? What's wrong with feeding ducks in the park?

If this guy has a scooter, can he go around Bare Island on a single breath? Now that would be an achievement and it would be so cheap to dive that way too.

Wednesday, October 8, 2008

Domestic prices not so bad anymore

Loose thoughts by Bjorn Landfeldt

Leisurepro has been a popular place to shop over the past few years. Normally, prices within Australia have been about twice of the overseas on-line shop prices and there have been endless discussions on on-line forums about the rip off. Back in July, the Australian dollar was worth about 95 US cents and about 5.85 Swedish kronor. Having a look at Leisurepro now and you can buy a cheap and nasty Bear suit for about USD 700 which after the financial turmoil so far equates to about AUD1100. Add $150 for shipping (or 15% sales tax if going there) and the nasty dry suit will cost $1250. It is true that it is hard to find a dry suit in Australia for that price but then again cheap Bare suits are not sold here, at least not in the shops I frequent. Now, all of a sudden, the price for scuba diving went up by 40% and it seems the Aussie dollar might continue to fall even further. Can I afford to continue diving? yes probably but I will have to use the equipment until it falls apart completely.

Why is it the Aussie dollar has fallen so sharply? Look at the Swedish krona for instance. Sweden is a much smaller country than Australia with a population of about 9M people. If anything, the smaller size shuld be a disadvantage when the financial markets crumble, but the Swedish krona has risen by about 30% compared with the Aussie dollar so far over the past week or so. One might start to think it is bad for a country to completely rely on digging stuff out of the dirt and selling to whoever might need it at the time. Perhaps getting serious about qualified products and services... Rudd!!!

Can't wait for inflation to take off.

Tuesday, September 23, 2008

5D Mark 2 could be the ultimate dive camera

Loose thoughts by Bjorn Landfeldt

Look at Vincent Laforet's blog. He tested the new Canon 5D mark 2 over a weekend and discovered that it has absolutely stunning low light performance and deals with strange white balance like no other camera. The following picture is a frame grab from some videos he took one night.

Not only is the video of excellent sharpness and resolution (shot at 1080i) it is taken straight from a RAW quicktime dump without any post processing. Now, if you have a camera that can take 21 Mpixel shots and full HD video and produce this quality in very bad light conditions, that camera should be an awesome dive camera. $3000 plus a couple of lenses plus a housing......

Saturday, September 20, 2008

Full frame or APS-C camera

Loose thoughts by Bjorn Landfeldt

For a few years now, the APS-C sensor format has been the dominating standard for the consumer/prosumer market and only in really high end models have we seen full frame 35 mm sensors. The Canon 5D has been at the lower end of the market at around $3k but there has been little movement here. There has been a lot of activity in the APS-C range though with models competing in a few different ranges and classes. Interestingly, there has been a sudden shift in the full frame segment with the almost simultaneous introduction of a few models. Nikon just introduced the D700, Canon the 5D Mark-II and Sony the long anticipated A900. Since they are all priced similarly at around $3000 there will be downward pressure on these models. In addition, it will get cheaper to produce full frame sensors over time so the gap between full frame and APS-C will shrink.

What does this mean?

Well, for one, it will become cheaper to get real high quality photos but there will also be some problems to consider.

What lenses should we buy now? I am thinking about getting some more lenses for my 40D, I would expect the lenses to be useful for 10-15 years or so and I won't have the same body for that long. So, what sensor will I have in my next body? If full frame will grow down into the prosumer end of things I can't buy EF-S lenses because they won't work with full frame. However, right now there are some interesting EF-S lenses around.

One lens I am especially interested in is the Canon 10-22 f/3.5-4.5 EF-S. It has gotten some really good reviews and test results show it is crisp, has really little barrel distortion, vignetting and chromatic aberration. It got better test results than the 17-40 L EF lens in tests I have read at a lower price. So, what to do?

Get full frame lenses now and miss out on the goodies from the APS-C platform or bite the bullet later if the next body will be full frame?

Wednesday, September 17, 2008

New Canon D5 Mark 2

Loose thoughts by Bjorn Landfeldt

Digital SLRs are becoming soooo good. We just read about the new Nikon D90 and the new Canon EOS 50D. Now the mysterious new silhouette on the Canon US web site has been unveiled, the 5D mkII.

DPreview has a pre-release review and major points are:

21 Mpixel full-frame sensor
ISO 50 - 25600 expansion (who needs light)
The new DIGIC 4 processor
Slowish 3.9 fps continuous shooting (after all 21 Mpixel)
vignetting correction
Live view with three mode auto-focus (including face detection)
No mirror-flip for exposures in Live View if contrast detect AF selected
Movie recording in live view (1080p H.264 up to 12 minutes, VGA H.264 up to 24 mins per clip)

What will it cost?

List price is US$2700, nothing really.

Saturday, August 30, 2008

Just missed the dive of a lifetime

Loose thoughts by Bjorn Landfeldt

Three weeks ago I dived Kurnell the leap with Tasos, Joachim and Thierry. During the entire dive we heard really loud whale song which was very nice. We got out at the steps and when we came up to the car park we met these two guys with BIG grins on their faces. They gave us the explanation of the whale song loudness because they had just had a humpback hale swimming past a few m away. One of the guys posted a note about the episode with a photo here.

Aaaaah! so close, how frustrating is that!!

Wednesday, August 27, 2008

New Canon 50D

Loose thoughts by Bjorn Landfeldt

Canon announced its new 50D DSLR a couple of days back. It looks very similar to my 40D but there are some improvements of course 15 Mpixel, live view with phase detection and faster CF card writing than the 40D. The good part is that the body probably will be compatible with the current 40D housings so divers will be able to purchase camera and housing in one go. That is unusual in the UW photo world.

DP review has a press release
and photos

Tuesday, August 26, 2008

Full circle

Loose thoughts by Bjorn Landfeldt

I recently found this old post card that my brother sent to me in 1982. Believe it or not, it is dive related.

At the time I sent him over to New York to buy me a Canon EOS 10 from a shop I found in an imported American photo magazine and he sent the post card back telling me how fantastic the camera was. When I saw the post card again something caught my eye it the top part. Looking closely I saw this sign of a photo shop, ADORAMA which I re-discovered last year when starting to purchase diving photography equipment.

My strobe arms and Ike housing were purchased from there. Back in those days ADORAMA was a small outfit on 34th street with what looks like a hand painted sign next to a bootery. I can't remember if I got the camera from ADORAMA back then but this is too much of a coincidence, I was destined to purchase UW photography gear. I feel a bond with ADORAMA now, a call to buy a housing for the 40D I have and better strobe set up, it's destiny.

In addition, I really think the post card has depth now, not only through the vice like grip on the bottom but also through the destiny thing!! Am I linked to Nick Migliore who took the photo in some mystical quantum photographic manner?

Thursday, August 21, 2008

That's a submarine

Loose thoughts by Bjorn Landfeldt

If ever I would get tired of putting on my dive gear I think I would befriend the Danish submarine enthusiast Peter Madsen and join him on his underwater trips. Peter has built the worlds largest home made submarine, which was put in the water in May 2008.

The sub measures 18 meter and weighs in at 36 ton so there would be plenty of space for me and a few bottles of Bordeaux. Apparently, he has managed to keep the build cost down to about $300.000. Apparently Peter wants to use it to go holidaying in the Mediterranean. Would create a stir at the docks in Monte Carlo I bet.

A photo series and some Danish commentary is available here:

Monday, August 11, 2008

Oil shale mining on the Great barrier reef

Loose thoughts by Bjorn Landfeldt

There is a proposal by a company called Queensland Energy Resources Ltd (QERL) to mine and process the McFarlane oil shale deposit in the Whitsundays, Queensland, 8 km south of Proserpine, 12 km southwest of Airlie Beach, partially overlying the listed Goorganga Wetlands and adjacent to the Great Barrier Reef and Conway National Parks. I wonder how anyone can come up with the idea to threaten a reef that is already under such stress.

There is a petition to stop this here

Friday, August 8, 2008

That's art

Loose thoughts by Bjorn Landfeldt

Just when I thought art was in serious risk of becoming boring I read about Sara Nilsson and David Aberg's groundbreaking work. On Sunday August 10 they have the opening of their exhibition called "C – Above and under". The exhibition takes place at Ransvik, Kullaberg in Sweden and involves a number of paintings of eyes that are displayed both above and below water.

I see an opportunity to tap into cultural funding for scuba divers here. How is this turned into something new and exciting?

Tuesday, July 29, 2008

Eastern Frogfish

By Bjorn Landfeldt

I saw this nice little Eastern Frogfish (Halophryne queenslandiae)at Bare Island last Sunday.

I was happy about finally being able to get a decent photo of them. Every time I have seen one, it has been hiding well under a ledge or in silt so photos have turned out dark, blurry or silty. This one was lying in-between two rocks on sand waiting for that cover shot.

Cuil search engine

By Bjorn Landfeldt

I just tried Cuil, a new search engine from some former Google people. The interface is nice, the search results are laid out side by side in columns with example pictures from pages. I found a curiosity though, simple searches such as "Sydney university or "Cuil" yields replies in no time whereas complex searches such as "Salvo rebel 12w LED" yields an error message saying something like our servers are overloaded at the moment. Could it be that the search algorithms are somewhat complex and this is the price to pay?

Sunday, July 27, 2008

Paragon Dry Suit

By Bjorn Landfeldt

I saw the paragon dry suit down at a local dealer after the dive today. It seems to be quite similar to the Northern Diver Cortex I have but there were some differences.

1) The suit is made of tough cordura as the ND suit is but this one felt softer and more pliable. The ND suit is tough as nails but it is also a bit restrictive. Without trying the Paragon on, I assume it is nicer in the water.

2) It has socks instead of boots. I think this is a good thing actually, it is better to put a decent boot on for rocky shores.

I have a problem that the ND suit traps quite a bit of air so that I need a lot of extra weight when diving dry. I suspect the Paragon is a bit better in this regard.

Thursday, July 24, 2008

Nice or Nuisance

I remember when I started to dive, how fascinating the Eastern Blue Groupers (Achoerodus viridis) were. For those of you who don't know them, these fish exist all around the coast of NSW, they are big, blue and extremely friendly.

Nowadays I am not sure. Since I started to take photos underwater I have realised that they more common than not just swim between you and the photo object, wrecking that one in a lifetime photo opportunity of the extra rare species. Are they a nice friendly part of our oceans or the hobby photographers worst enemy I wonder?

Salvo Rebel 12 W LED review / opinion

This page contains my opinions of the Salvo 12 W LED canister light. I am putting this information on line since I couldn't find much in terms of testing before I ordered it. I am not in any way a light professional and I don't have access to proper light meters so I cannot provide any hard numbers on the output. What I can do is to provide my own thoughts and experiences with the light.

First, the cannister is very small and very light. There is no problem mounting it on a back plate or on the webbing of a harness, it will not be in the way or feel heavy. In fact, I will try to mount it under my Ikelite housing at some stage for night dive photography and see how that works. The light feels very solid. Since there are no parts to open apart from the light head for recharging it all looks like a light that will last many years and the LED will not break easily either so overall, a solidly crafted package set to last for a long time with minimum maintenance. I will need to use the light for a while before being certain about the quality of the steel etc. but it all looks good.

Some facts:

Battery pack, 5.2 Ah Li-Ion
Burn time, 5 h
Output, 750 Lumen
Temperature, 5600 K
Cannister weight, 1.1 kg
Cannister size, 19 cm x 5 cm (diam)
LED manufacturer, Ostar

Light beam:

When switching the light on I was surprised at how much light was leaking outside the 6 degree beam listed on the Salvo site. Personally, I don't mind since I believe this will just help illuminate the reef around me and help me spot interesting critters. However, it also means the output is not concentrated on the spot so people who want a strict pencil beam for wreck diving etc. may get a bit disappointed.

The picture above shows the 6 degree spot in the center and the surrounding illuminated ring. In my opinion, the surrounding ring should be bright enough to illuminate a reef quite well (compared with my old c4 1 W LED torch). The photo is very much underexposed to bring out the center spot.

The below picture shows the spread from the light head. The head is about 50 cm from the wall and the large ring about 1m in diameter which shows that there is quite a large illuminated area. The camera can't separate the spot from the outer ring in the photo since the illuminated area is completely overexposed and all highlights are clipped. Also, this photo shows better than the top photo how bright the outer ring is.

In order to get a feel for how strong the torch is, I put it next to my backup torch, a Salvo Rat 3 W LED. Now, when I got the Rat I thought that was really good with a beam that went far in under ledges and nice bright light. As can be seen from the photo below, the Rebel on the right copletely kills the Rat on the left. It is hard to see in the photo but there is a wider ring around the rat spot as well but compared with the Rebel it is almost invisible. The two torches were placed side by side about 1m from the wall in the photo.

In the Water

I went diving with the torch for the first time on July 16. My immediate reaction was that the light was very bright. Greg brought his old 20 W halogen cannister light and at first I thought he was running low on batteries when he turned it on and after having seen the Salvo on. For Sydney divers who are familiar with Bare Island in order to get a feel for how bright it is, it clearly illuminates the fort on Bare Island from the boom gates (200-250 m).

I tried to take some photos from under water but it was impossible to hold the torch and take meaningful photos. Since the light source was so close to the camera all I got was a coplete whiteout from the beam, backscatter and nothing of the target wall. However, if looking at the photo below one can see the sand bottom and get an idea of the light spread. The torch would have been about 1 m above the sand at this point.

The torch is brilliant for reef diving. As I suspected the outer ring illuminates a wide area enough to see the night critters so as you dive, fairly much the entire field of vision is lit up decently. The center spot is strong enough to penetrate deep into caverns and light up the insides of caves. It was difficult to tell how far the torch penetrates since this is dependent on some quantifiable measure of visibility and particles in the water at the time. However, the reach was much further than the halogen spot (focusable).