Chris Ross

Hi Adventurer, i'm sorry if you feel it's a personal grudge, believe me there's nothing personal about it. It's addressing the subject not the poster. If I believe a post is incorrect or misleading in someway I'll respond to it. I do believe you are missing the point, I am in no way claiming these are perfect to the corner, it's merely to point out these images come from a dome positioned a long way from the optimal point. Some people could care less about corners others want to be sharp to the corner at 100%. Myself I'm kind of in the middle, I want decent corners but recognise that there are diminishing returns. On the subject of the Ikelite port I am referring to the compact dome port. This one: The dome is said to be a small segment of an 8" dome and is about 158 dia x 46 high by the specs The dome only rises about 20mm above the edge of the plastic port. The 8-15 would need to sit right up forward in this dome to avoid vignetting with the entrance pupil almost at the edge of the plastic part of the port to avoid vignetting. The radius would be 100mm and this would place the centre of curvature somewhere around 70 -80mm behind the entrance pupil of the lens. I could see the regular 8" dome having the entrance pupil around 43mm out as you said as that dome is also not a full hemisphere. I'm not saying I would want this situation with a badly mis-positioned dome just that people use this lens/port and are happy with it. I don't doubt for a minute your findings with the chessboard test, I'm just suggesting that the results in the images taken are not that terrible if they are out by 5-10mm. If you want to fine tune the positioning of your dome, more power to you. In the examples you referred to, my eyes I couldn't see a huge improvement in changing the dome position.

I think we need to recognize a few things when comparing strobes. First GN is generally measured in the centre where it probably least useful and of course there is no standard for measuring and reporting GN, it will change for instance between indoor and outdoor test as the walls bounce light back in. GN are regarded with suspicion even on Land based flashes. Second to compare how much we are getting out of the strobe we need to include beam angle - the 580 EX which I own has a GN of 58 at maximum zoom concentrating the light into the field of a 105mm lens. It shrinks to GN of 15 when covering the field of a 14mm lens which is commonly what the UW flashes achieve for field coverage or a little more. Looking at the light required to fill a 100deg cone with light versus a 130 deg cone, and plugging the results into a lux calculator, then assuming 1000 lumens illuminating the circle at the end of a 110 deg cone gives 103 lux and a 130 deg cone gives 61 lux at the same distance of 1 meter. Back calculating, you would need 1700 lumens to achieve the same the same illumination on the subject (as a 100 deg cone) with the bigger coverage of the 130 deg beam angle. So this means to achieve the same GN, assuming even illumination over a 130 deg cone, as you get from a 100 deg cone you need 1.7x as much light and hence 1.7x the battery power. This compares apples with apples and shows that while a 130 deg field might be nice it has a price associated with it. So the INON doesn't need as much power to illuminate the same subject but you have to be more precise in positioning its beams to fully cover a wide field compared to a 130 deg strobe. this demonstrates why the Retra chews batteries faster.

yes this is true, but only if you use it. If the Z-240 is giving you enough light then the Retra in the same situation should also draw less as you've turned the Retra down from full power. So only if you use the extra power the life will go down. There is also variation in how efficiently the strobe uses the power it draws, I recall discussion that the Z330 had higher guide number full power but had very similar number of full power flashes confirmed by someone doing some testing. It was a long time ago now, so I may have mixed things up. The only way this could happen is the efficiency of the charging circuit improves. You have a number of steps in the circuit, first up an oscillator and inverter to increase voltage to capacitor, then the triggering circuit with it's own high voltage transformer and a thyristor to control the cut off of the strobe. All have thermal losses associated with them. However fundamentally a higher power flash is probably less efficient unless you make change to the circuit charging the capacitor. If you draw more current you lose more to heat passing through the same resistance by the equation Power = Amps^2 x R.

There are lots of reasons why the flange distance might vary between brands, it's only important to be consistent within a brand or more specifically a lens mount such as Canon EF, Nikon Z etc. For example Nauticam Canon RF housings place the camera back further in the housing such that the RF-EF converter if where the flange of an EF mount camera would be relative to the flange. This is important as it means the EF port chart applies to EF lenses used on the RF-EF converter and the same zoom gear is used. This means that the upgrade path is easier for a Canon EF user to upgrade to RF. Initially they can bring across their EF lenses, zoom gears, ports and extensions with no additional investment. Nauticam have done the same for Nikon Z mount housings. Other manufacturers may have done things differently. In the end it doesn't matter if they move the flange distance around between different lens mounts as they can compensate for it with different extensions. They probably start with the shortest fisheye lenses so they can be used without extension in the small dome ports. For example the Panasonic 8mm fisheye uses no extension on m43 housings, on Canon EF, the Sigma 10mm fisheye and Canon 15mm fisheye use no extension etc. The shortest lens they design for is probably different in each lens mount. They also take into account where they place the housing zoom/focus gear drive in the housing and the need to mate up with that.

First of all allow for the fact the Air Niugini may have trouble on connections. Read Don Silcocks account on the best time to go, you probably don't want to go in the wet season. Different sites have different optimum times - So for example, Nov is good at Tufi and also Walindi, where May is also good but it's not so good at Tufi. Here is a link: https://indopacificimages.com/papua-new-guinea/guide-to-diving-papua-new-guinea/ I went in May last year to Walindi and had a good trip. I did mostly wide angle with CFWA on occasions. Another diver did mostly macro. This was during the doldrums, though there was some wind. Quite hot and humid. November is also a good time. Some days were a little rough trying to get out to the sea mounts which are the real feature of diving there with big schools of Barracuda, big eye trevalley and massive schools of plankton feeders with various triggerfish and pyramid butterfly fish etc in big numbers. Also sea fans with pygmies, Colurful anemones with clownfish etc. The sea mounts are relatively deep and diving on Nitrox is an advantage. My trip report is here: Consider though that even though you are there 4 weeks you might lose a day of diving to transfers as you fly between each site and you could lose another full day to travel getting there with the risk of a cancelled or missed connection if going back through Port Moresby which you would have to do if you dived Tufi /Tiwali with Walindi/Lissenung Island and possibly also travelling between Tufi and Tiwali. Some Flights to Kaviang stop in Hoskins (airport for Walindi) (or is it some flights from Kavieng stop in Hoskins??) so you don't have a connection to make to get to your next spot. DO your research to minimise connecting flights each one carries the risk of losing an additional days diving.

The EP-14 as I recall is set up to use Olympus mini flash which used to come with their cameras as is the Nauticam housing so if it fits in the Nauticam housing likely it fits in the PT-EP 14. The only thing that might be an issue is overhanging the camera at the back. You would still need to trail fit it though to be certain in case there is anything protruding inside.

You need to read the fine print of your insurance - a lot of them state items are not covered if checked, unless the airline forces you to check the items. I'm not sure where you are flying to but in the US, domestically while there may be limits they seem to be ignored and it's a race to get on first and get locker space. Seems the same for a great many airlines flying out of the US though budget airlines will enforce it so they can charge you check things. I would think it's toss up which to check - I would base it on weight and value and what I could get away with packing in the carry on. Ultimately the solution I think is to base your ticket purchase on carry on policy and book far enough ahead to get a good fare.

The issue you will find with Fujifilm camera is limited UW housing support. The only housings are an Ikelite housing or perhaps a seafrogs housing. If you look at the ikelite housing, it's $USD2195 at Backscatter and you need to add a port and other components to that. They only support the Fuji 80mm macro lens in the port charts. You are limited to wired flash - no fibre optics. Seafrogs are a lot cheaper but you get what you pay for, for example it notes the following controls can't be used in the housing: Front command dial Rear command dial Aperture control of the lens Focus stick (Focus lever) It only supports the 60mm Fuji macro lens. Don't buy the Sea Frogs vacuum system, it can only be used to test on land, can't dive with a vacuum pulled which defeats the purpose. But you definitely want a vacuum system! To this you would need to add clamps and arms for a strobe plus a strobe trigger, I would suggest the INON S220, a compact reliable little strobe at a good price point. quite OK for macro. I would also seriously suggest considering other camera system options. Fuji is not well supported underwater and housing availability is limited. All you have now that you can use UW is the camera body. Nauticam used to support them, but the XT-5 housing is discontinued. It seems to me that it is a bit of a dead end for UW photography. Sea Frogs while they will work are a bit kludgy and the wide angle ports are universal and not necessarily provided with the correct extensions for best performance. There's only a handful of (admittedly very keen) users of Fulji on this site. See is you can find a second hand micro43 system, maybe an EM-1 MkII? the 60mm macro lens for this system is very compact. The Nauticam housings for them are great as are the Isotta. People are very happy with the AOI housings for the OM-5 and OM-1. Growing a system like this is a lot simpler as a great many lenses are supported with the proper extension provided. If you are learning a TG-7 with a strobe is a great option for macro, very compact. It of course has limitations withe small sensor and lack of full manual controls but a great many people are happy with them.

Yes, the lens only gives a relatively small increase in field and you don't to be using some of that increase up. 16mm becomes something like 21mm in a flat port, so if you have to zoom into 23mm you are worse off. Let's see what the vendor says.

Just to clarify did you try it in air and you haven't gotten it wet yet? Can't say for certain but this may change when UW. But before you get it wet try talking to your vendor to see what they say, there isn't much out there about this lens. The purpose you state is what the lens is intended for and it should work on your lens as designed I would think.

Welcome aboard Cameron

Exactly. You might get a slight variation in light output with each pulse but effectively it stays on, just the pulsing reduces and spreads out the capacitor so it can stay on longer. I would guess that HSS sync capable flashes mostly work by pulsing the capacitor for as long as they receive light from the trigger (rather than trying to exactly match the master flash out put exactly.

I've not been but know a guy who has been multiple times on MV Oceania/ mV Febrina operating out of Kimbe Bay PNG , It's on the outer edge of Polynesia I guess. here's some info about it: https://indopacificimages.com/papua-new-guinea/guide-to-diving-papua-new-guinea/guide-to-diving-new-britain/new-britain-diving-an-overview/

HSS works by imitating a continuous pulse. The capacitor can generally only do a limited pulse length and if just fed through the normal circuit for longer would run out of charge. So it pulses and this has to be like a duty cycle controller to reduce the current drawn and so enable the pulse to run for the entire time the shutter is open. With the high frequency each line of pixels receives multiple pulses as the shutter curtain travels upwards, as the shutter curtain window narrows with faster shutter speeds each line of pixels progressively sees less pulses this is why power goes down each pixel sees a lesser number of pulses as they are uncovered for less time. For example if the frequency is 100 kHz, then there will be 100,000 x 1/320 = 312 pulses on every pixel.

Looks very Good Pavel, I would guess this streamlines your model range a little as it will fit any housing with enough space to route the hotshoe cable. Out of interest what is different about the Isotta and ikelite M16 housings that requires a different version - perhaps something about the way the o-ring seal is achieved? There was a related question on this recently.

To those wanting to fit triggers in the A series Sony housings, the new external trigger that UWT has put out may be of interest, it only needs space for the hotshoe cable inside. Assuming it works as advertised it could be a good option. There is a an announcement onsite currently here:

I think you will find this will depend on the shutter speed. at very high shutter speeds like 1/4000 sec the band crossing the sensor is quite narrow. Most often in UW work the SS will be in a 1/320 - 1/500 range and all you are trying to achieve is prevent the black band in the image and the opening that moves takes up a large portion of the sensor and everything receives multiple flashes I suspect even at the highest shutter speeds it might receive 5-10 pulses or nore depending on pulse frequency and speed of the shutter curtain.

a 5D IV is quite an old camera now, live view was quite a new feature back then. Live view as you know uses data from the sensor for AF as the mirror is up and the phase detect AF chips can't be used. The Phase detect sensors could AF the camera but the on chip AF is just not up to the task unless there's plenty of light available.

This is talking about human vision and it doesn't apply to pixels they store every photon they receive. This threshold refers to enough contrast that human vision can say it's a different shade or brightness. The object still reflects the light it just can't be detected against the background brightness - a signal to noise issue. If you can pick up the object as backscatter with a single pulse shot and it stays on the same pixel then you will also see it with HSS. I estimated that a 1/250 sec exposure sees something like 80 pulses and the object needs to move very rapidly to get to an entirely new set of pixels. If a particle sees only one pulse it is about 6 stops under exposed roughly speaking. Regarding video lights they are usually dimmed by a similar mechanism to HSS, rapid pulsing, so 50% strength comes from the light being powered on about 50% of the time, the cycling is rapid enough we can't see but can be a problem with video causing flicker.

Thinking of ways to quantify % of liveaboards in the Red Sea, so I went to liveaboard.com and they list a total of 311 liveaboards worldwide, while in Egypt they list 42. They probably don't list all options in Egypt, but likewise they probably don't list all options worldwide. They have for example 52 in Indonesia and 24 in the Maldives. I think this shows that the safety performance in Egypt is very poor compared to the rest of the world.

I'm sorry I have no idea what you are talking about. In HSS each pulse illuminates the subject and the backscatter particle with the same intensity of light. If the particle moves to a different set of pixels between pulses it won't be as bright as the pixels where it used to be don't get more light. If it stays on the same pixels it gets the same amount of light as the subject and is just as bright as it would be in a single exposure that provides the same exposure on the subject. The pulses may be short and have less light but they have to add up the same amount on your subject for the exposure to be the same. This is achieved by using more of the stored energy in the capacitor and/or wider aperture and/or higher ISO.

I think you are somewhat missing the point, this lens performs acceptably behind a dome where the centre of curvature is around 80mm behind the entrance pupil. Sure the pics in the link I posted are relatively small, but they are enough to show that they produce pics a lot of people would be delighted with. It basically shows that the lens is relatively tolerant of misplacement of the centre of curvature. If you look at the size of this port, the dome section is only about 20mm high so the lens focuses right down on the port allowing you to get very close to your subject - which makes a significant difference for CFWA, the subject becomes all the more prominent in the frame and small differences in distance makes a big impact with a fisheye lens. But this of course involves a compromise, with a small deterioration in corner performance.

Thanks @adventurer for your response, I should mention that I spent some time comparing the two different extensions with the 8-15mm though it didn't help that the image scale was different in them and spent a lot of time flicking back and forth between the two images till I thought i was starting to hallucinate. So I downloaded the two images and cropped an equivalent part of each and pasted in a single image to compare them, here it is 30mm is on top: Now I may need to get my eyes checked but the difference doesn't really set the world on fire, if anything there might be a bit more micro contrast on the collar to the right of the 6 in the serial number, but really not much in it to my eyes. To be fair there may be more to be seen in the original tifs, but based on this I think I could use either one happily. It would be interesting to see a similar comparison for a rectilinear lens.

A rectilinear lens is always going to be more sensitive to this than a fisheye lens, the way they render lines is fundamentally different to a rectilinear. It actually not possible to make a rectilinear lens with a 180 deg diagonal field of view, have a look at the formula for rectilinear lenses it falls apart when you try to solve it for 180 deg. Basically the ends of a straight line need to be at infinity to be rendered rectilinearly. If you look at the infocus field for a fisheye it's a curve not a line, almost like it was designed to be used behind a dome. I have never doubted that a rectilinear needs to be close to the ideal position. Fisheyes however are another story. I don't have the maths to describe it correctly, but experience from lots of people posting about the Canon 8-15 show it's nowhere near as sensitive to dome position. I don't doubt having the centre of curvature 40 or 50mm away from the entrance pupil will have some impact, but if you are within 5-10mm you will be in pretty decent shape. Some of it seems be down to the way the image is compressed in the corners, the image scale is a lot smaller and kind of hides aberrations by shrinking them. If you want to do these investigations, then more power to you of course, but if you don't fret about your image corners too much the Nauticam port charts seem to be pretty decent.

That may well be but Nauticam for example suggests 20mm of extension to compensate. I don't think 2mm will make a lot of difference in your images, most port systems only go up in 5 or 10mm increments depending on the housing system you are working with.