Chris Ross

with diffuser, the without diffuser shot shows only that you should always have a diffuser on that strobe.

Server problems I believe. Seems like it's sorted out now.

I'm not sure exactly what you are saying with regards to a larger air gap between the port glass and lens, but basically the point in focus at 1:1 is a constant distance from the sensor and if the port is longer this eats into the distance so at 1:1 (for example) you have less space between the end of the port and the subject if the port is too long. Looking at the EMWL another way, if you've spent all that money why compromise to save the price of an extension ring?

I plotted up the brightness from the centre and the square just inside each ring plus the outermost square at the level of the "X"axis horizontally out from the centre. The X axis of the plot is arbitrary values with ) being centre and 1, 2 and 3 being the 3 rings on the target. Imported each jpeg in PS, convert to greyscale then LAB colour to get luminance values. Here is the plot: You can see the YS-D3 has more dramatic fall off and the Retra has the same brightness at points 3 and 4 even though it started off with lower luminance in the centre. The ikelite has roughly the same curve shape as the YS-D3 just brighter through out the range. Basically this means the Retra spreads its light out more evenly with less fall off. You need the plot to judge the difference because the human eye is terrible at such comparisons. Basically what this means that at constant centre brightness, the Retra has the brightest edge to the light cones.

To my eye the Retra looks most even but it is difficult to judge with different centre brightnesses I think the photos really need to be converted to plots to judge properly. I think also for example the retra has the target a bit folded so the bits angled away from the camera seem darkened. You can see in the plot provided, I think its from Retra the RF pro mirrors the seacam and the curve is flatter than the DS-161 ikelite flash

Diopters don't work as well if there is too much gap between lens and port. You could probably just use what you have now and get the right port to go with the EMWL when you go that way - The wide angle of the EMWL will probably impact that more so and getting the right port more critical. The other impact of course if the port is too long is that you lose that much working distance.

The Tokina 10-17 would be a fine option for wide angle work and with the zoom will adapt for pelagics quite well. Going for the widest option will also encourage you to get closer and this is probably the No.1 thing you can do improve your photos. at 17mm the field of view is equivalent to about a 21mm lens (FF equiv) or 14mm or so lens on an APS-C. SO it covers a full frame fisheye, the WWL max view which is about a 14mm full frame equivalent and about half of the range available with the 10-18 zoom. All in the one lens. Fisheye zooms cover more range of field of view than their zoom ratio suggests as the barrel distortion means the centre of field is magnified so when zooming the area covered on the horizontal axis decreases more as you zoom in. This table shows it: APS-C coverage horizontal vertical diagonal 10mm fisheye 144 92 180 17mm fisheye 81 53 98 WWL max 122 100 130 10mm rectilinear 99 76 109 18mm rectilinear 66 47 76 The advantage of the fisheye over the other options is it will work in a 4"dome, making CFWA easier and can Replace about 2 1/2 lenses. You can add a 1.4x to it and you have a complete coverage for everything bar macro work in one very small package and it very light for travel and manoeuvrable in the water.

A fisheye zoom like the Tokina is quite a good option, though on a Sony camera you want to adapt a Canon lens not Nikon. The Nikon mount lens is screw drive AF and won't work on anything but a Nikon F mount camera. There is an adapter that supports screw drive now I believe but I wouldn't go this way if you can use electronic AF with the Canon. you may well be on your own if want a zoom gear with the Seafrogs housing though. Whichever lens you choose - a zoom is going to be a better option for flexibility. Also with regards to natural light photography, even then you benefit from being closer to your subject, you can see in the example file that the colours start to fade out further from the lens, this being due to having to travel through more water to reach you than that from closer objects. Not as dramatic as strobe light , but still there and you also have less water between you and the subject so less particles and distortion from the water. Plus it's a good habit to get into.

The 100mm macro would work nicely for your smaller subjects but you would be a bit distant for the larger subjects. a 150mm subject you might be about 300mm away from and a 300mm subject you would be close to 900mm away.

Yes, but even then you can back button focus as the depth of field is enough, video and fisheyes don't mix well it seems.

Of course if it looks the right size and won't screw in you are dealing with imperial threads.

the AF for fisheye lenses is not particularly challenging, the Metabones with my olympus and 8-15 is fine for AF. I think the Metabones is a viable solution if you want to use a fisheye.

Quite possibly an M6 or M8?, you could try in any hardware store then knowing the right thread order the correct screws. If you have a Nauticam housing it will likely have a screw about that size you could try out, mine seems to have M6, M8 and M10 screws. If you find one that fits you can measure the OD with calipers and consult a thread chart to work out what is what.

The wet lenses use a bayonet mount (apart from the original WWL-1 which has an M67 thread) and the while bayonet mount screw onto an M67 threaded port the issue is that the bayonet attachment for the port has a U-shaped groove and is the port lip is too wide it won't screw on. It might work on some ports but not others. One work around is to adapt a Nauticam port to your housing and this will work if you can get the right adapter length/port length combination. If you have a Isotta or Sea and Sea housing that uses N120 ports you can adapt the Nauticam port directly by changing the lug plate over to a S&S/Isotta lug plate.

It really depends on your subjects, expectations and to some extent what type of waters. Strobes really can make a big difference to the type of photos you can take. Certainly you should be able to white balance photos from clear tropical waters, very green temperate waters might be more of a challenge. The 12mm lens I've not heard much about but it is not particularly wide in UW terms. The use of wide angle lenses is less to get a wide angle of view and more to allow you to get closer to your subject. The less water between you and your subject the better. You may be thinking of no strobes initially but I would think you might be better served with a zoom lens like the 10-18 or similar which I would think would be more adaptable in the long run. On the vacuum pump don't get the Seafrogs vacuum valve as it is not water proof, many people use the Vivid leak sentinel you can contact them to get a valve with the right thread to use on Seafrogs.

Basically go to a fastener store with the housing and find a stainless steel cap screw with the right thread. Canada is metric but being next door to the US, threads could be imperial. Presumably they screw into a tapped hole on the housing?

Basically while you can still Raw process the TG-6 gives you much less latitude to boost shadows and and boost contrast before noise and processing artifacts intrude.

the only reason to seal the outside might be aesthetics and to try to strengthen it against scratching and also sun protection. It is made to be inside a composite structure so UV stability may not be great. In round numbers the buoyancy should be about 950 grams/litre (1000 cm3)

I would be trying to add some buoyancy below the housing, your original query was around the effort required to twist the housing as all of the buoyancy is above the housing. I have a similar issue with 1200 gr of buoyancy arms above the housing. I would think you should be able to find some type of board to bolt to your housing base using the tripod holes and securely attach something like half of your stix floats to that. You could shape a piece of marine ply to suit or some other type of waterproof board to attach to housing and securely attach your floats.

this is relative to the same strobe, so if any given strobe is pulsed for less time it will not reach the same peak/average temperature so it will be warmer than its maximum power temperature. It doesn't apply comparing big round tubes to short linear tubes.

As I understand things strobes emit a full spectrum centred around their colour temperature and they do this by generating a plasma which glows giving a black-body type continuous spectrum centred on a particular wavelength. Technically it produces grey body radiation which is transparent to its own radiation. This wavelength is what defines the colour temperature produced. The temperature achieved inside the tube corresponds to plasma temperature achieved so 4500-6000 degrees kelvin (Kelvin = degrees C plus 273) The peak wavelength moves to shorter wavelengths as the current density increases due to the plasma getting hotter. If the strobe is using small linear tubes the current density needs to be higher to match the output produced from a larger tube so light is bluer. The light produced is proportional to the volume of gas that is excited into a plasma. So physically large tubes can use lower current densities and their light tends to be warmer. Similarly a shorter pulse will shift warmer as the shorter duration means less energy is added to tube so peak temperature reached is lower, color temperature lower and peak wavelength longer.

It's good that they do standard comparison tests of strobes, but when I last looked the only way to find them was buried in individual videos be nice if they had a central site where you could find their data to directly compare strobes you are interested in. I find I am really not a fan of video reviews they are nice enough to watch but I'd much rather have a written review where I can skim to the interesting bits.

I'm as baffled as you about green water turning blue, you can do it in post processing but the diffuser has little to do with it.

I'm not sure how this relates to my comment (quoted by you) I made no mention of turning green water blue - perhaps it applies to another comment.

Indeed, It's really WB method independent and requires no more thought than doing the standard WB adjustment on your subject. The main point if that it really only is a big benefit in clean tropical waters. I've left the 4600K diffusers on in temperate Sydney water and the photos come out just fine, but I don't see a big benefit for it in that situation.