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NUPG April Meeting Report



This month Alex Tasker gave us an insight into photogrammetry and his journey so far using this technique underwater.

Our usual focus at NUPG is capturing the beautiful scenes we see underwater in 2D, so turning these images into something in 3d so you can move around an object or underwater area on your laptop is a different concept and style of photography. Alex explained some of the history and theory of how this works and explained how he first got interested in this style of photography.

The historical side of things took us back to the thousands of images taken from spitfires in WW2 and the intelligence techniques that spotted the V2 rocket project. Alex’s own journey with photogrammetry first started with East Cheshire Sub Aqua Club’s Highball project and their aim to create a 3d model of one of the highball bombs in Loch Striven to allow non-divers to see what we are able to visit.

The theory started off making things sound relatively easy. The aim is to take lots of overlapping photographs of the subject from different angles. If there’s enough overlap each photograph has common points which the software can identify. The software can use both stills and video (by extracting individual frames from the video) and has the potential to use images from multiple sources to create the final 3d model, so the options on what camera to use are wide. After identifying the points in each image that match those in another image in the set and passing through multiple phases the software (hopefully) pops out a 3d model.

Alex’s first attempt was encouraging, on our ‘NUPG warm-up’ day in Capernwray last year he took hundreds of photos of Thunderbird 4 and produced a good 3d model (he obviously had 2 very patient buddies). Taking the photos that allowed this first attempt to work seemed easy, there was plenty of natural light and good visibility, the lesson learnt on this particular occasion was more about the patience required waiting for a laptop to process the images (or grind to a halt as the case may be). With the aim of the highball in mind though he needed to target objects in bad visibility, leading to trips to other well-known quarries where bad visibility and gloom are more readily found and an attempt to get a model of the hydrobox at Stoney Cove. The visibility on that occasion was so bad that the software thought some of the ‘muck’ in the water was actually part of an object and attempted to make it part of the model! This experiment also highlighted the challenges of getting images aligned, in bad visibility you need more overlap. The resulting model worked well for the top of the hydrobox but not the sides unfortunately. As with any form of photography though, practise is the key, so I’m sure another trip to the hydrobox will be on the cards this year.

At the beginning of March, Alex headed to Vobster Quay for a weekend to take part on the IANTD Photogrammetry course run by Tim Clements. He thoroughly enjoyed the course and got to pick up some tips from the likes of Simon Brown and Marcus Blatchford, who have a wealth of experience on this subject and have produced some amazing models (including entire wrecks and models that combine both underwater and drone photography). The course also got Alex thinking about the use of ‘angel lighting’. He’d been using his regular camera for the stills and attaching a video camera to the rig to collect additional data, having strobes and video lights on the same rig did add complications. By having his buddy carry the video lights it made using the video camera easier as a backup, gave his regular camera a better chance to focus and helped him easily know exactly where to find his buddy (not to mention giving his buddy something to do so she doesn’t get bored!)

Getting the images for photogrammetry is something any of us could do with our existing cameras. The challenges then become the amount of data generated from those images and the amount of processing power needed to turn them into a 3d model. There’s an amazing amount can be achieved by doing this though, from creating models of coral reefs to showing non-diving experts details of underwater wrecks. It will be interesting to see where his journey takes him over the coming months.

Winner by Justin Beevor

The monthly competition theme was Cephalopods. We had an array of fantastic images; the overall winner was Justin Beevor’s coconut octopus. Congratulations also go to Glynn Phillips whose octopus shot came in 2nd, and Maggie Russell who took 3rd place with a nicely isolated squid and also won the Compact category with her octopus entry.

The next NUPG meeting will be on Monday 13th May. This meeting will include talks by Roisin Maddison and Donovan Lewis on Videography and Sharks, as well as the NUPG AGM. The competition theme is “Action”.

For more information about the NUPG please visit their website by clicking here.

The Northern Underwater Photography Group (NUPG) is an organisation of like-minded people with an interest in taking images underwater. The group meets in Manchester but membership is drawn from around the North of England and further afield. Meetings are monthly and previous speakers have included Alex Mustard, Martin Edge, Alex Tattersall, and Scubaverse's own Nick & Caroline Robertson-Brown. Find out more at

Freediving Blogs

British freediver sets new national record with 112m dive



British freediver Gary McGrath has set a new national record at the prestigious Vertical Blue freediving competition in the Bahamas.

Using only a monofin for propulsion, Gary swam down a measured rope to a depth of 112m (367ft), returning to the surface to receive a white card from the AIDA International judges to validate his dive.

Gary, 41, held his breath for three minutes and 13 seconds to complete the dive.

Freedivers descend underwater on a single breath of air and the atmospheric pressure on their bodies increases as they go deeper.

At 112m deep the pressure is 12 times greater than the surface, meaning the air in Gary’s lungs would have shrunk to less than a twelfth of its original volume – around the size of a golf ball.

Freedivers train to cope with the physiological strains placed on their bodies by their sport, and Gary uses his background of yoga and meditation to help his physical and mental preparation for deep dives.

He has also had to overcome physical challenges after contracting Covid last year during preparations for a previous national record attempt.

Gary said: ‘Diving below 100m is a totally unique environment, it’s my therapy. 

‘This year has been extremely challenging for my mental health and freediving has helped me overcome that for sure. 

‘At depth I have complete isolation from the everyday world we live in. Down there it’s just me and nature. It’s that escape that all freedivers crave. 

‘There are moments of extreme mental clarity and purity that I can only achieve when underwater. The flow state that a deep dive allows me to experience is unique and addictive.

Gary, originally from Twickenham, began freediving in 2006 and has been competing since 2008.

A former tree surgeon, he became a professional freedive instructor in 2014, and he and his partner Lynne Paddon run Yoga and Freedive Retreats in Ibiza.

Remarkably, he completed his 112m national record dive on Tuesday (August 9) despite being forced to compete wearing a borrowed monofin which was a size too small for his feet.

His entire kit bag containing his monofin, bifins and two wetsuits was lost by an airline as he travelled to the competition.

Despite his careful preparation, Gary said he suffered nerves on the morning of his national record dive, and relied on a phone call to his partner Lynne, who helped him focus on breathing techniques and visualisation to calm his nerves.

Speaking immediately after his dive, he said: ‘That was all for Lynne – this whole week has been about her. I could not do it without her. I hope that everyone finds someone they can click with, it’s the most magical thing in the world.’

Gary also thanked supporters who helped him to crowdfund to raise the money needed for him to travel to the Bahamas and compete.

Vertical Blue is considered one of the most elite events on the freediving calendar and has been dubbed the ‘Wimbledon of Freediving’.

Owned and run by world record freediver William Trubridge, the event takes place in a 202m (663ft) deep sinkhole known as Dean’s Blue Hole, off the coast of Long Island.

The previous British national record of 111m was set by Michael Board in 2018, also at a Vertical Blue competition.

All Photographs courtesy of Daan Verhoeven (

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Miscellaneous Blogs

Film Review: Thirteen Lives



Ron Howard’s recreation of the 2018 rescue of a Thai junior football team is impressive. Even though we know what happens in the end the tension and drama played out is palpable.

On 23 June 2018, 12 members of a Thai junior football team, the Wild Boars, and their coach became trapped deep in the Tham Luang cave system by rising flood water. The film details the incredible international rescue efforts that ensue. And Ron Howard has judged the tone perfectly. There is no Hollywood glitz and glamour and the two leading actors: Colin Farrell and Viggo Mortensen, who play John Volanthen and Rick Stanton respectively, capture the intensity of the situation perfectly.

The diving scenes are claustrophobic in the extreme. Although I suspect that the visibility was even worse than the film depicts as you have to be able to see something in the dramatization! All the way through the film I found myself shaking my head in disbelief at the extraordinary feat these divers pulled off. The skill and bravery required still impresses after watching films, hearing them speak in public and reading about the rescue.

I loved that, whilst the divers took centre stage in the film, the heroic rescue efforts of the water engineer and his team was also given the attention they deserve, as well as the incredible Thai Navy Seals and the thousands of people that flocked to the region to help.

Thirteen Lives is a must watch movie about an incredible cave rescue. It’s sober tone hits the mark. The cinematography is skilled and creates an impressively tense experience. It is available on Amazon Prime right now.

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