Chris Ross

Assuming the price in France includes VAT, that explains a good portion of the difference. Technically I would guess you are supposed to declare goods coming into the country and pay the VAT upon return as any of these items would exceed the duty-free allowance for travelers. In addition to the warranty issues, you need to consider the policies of the local distributors for the cameras in question. For example I understand that Nikon USA won't even do paid work on a non-US model camera, at least that was the case a few years back. The issues are that warranty and support aren't free, the margin in country pays for the support infrastructure. In some cases there are excessive margins, but that is steadily eroding due to the ablity to buy goods from overseas sources and online sales in country.

Thinking about that maybe using the 90 mm macro behind a small dome might be enough? Losing the flat port magnification you would be equivalent to maybe about a 70mm lens behind a flat port.

No reason you couldn't do it, apart from being potentially unwieldy. Probably be fine getting on and off the boat in calm seas, also consider if currents might be an issue. I would also consider that if you could double your light output by adding an extra flash, that is one stop of light. Your might get maybe 1/2 - 2/3 stop more light with the extra flash. Depending on where you are on shutter speed you could achieve more or less the same results with one stop more on ISO. Maybe try something like opening up by 1/3 stop and 1/3 stop higher ISO?

Seems like a massive leap going to a phone housing, you'll not have strobe light as you know. Have you considered going part way, something like a Canon G7X would fit into something a lot smaller and be reasonably versatile particularly for wide angle. Macro not so much, certainly do-able and better in terms of small subjects compared to what a phone could do. You could get away with smaller strobes like the INON S-220, possibly even a single strobe. I would kind of think of a phone housing as producing a record shot, not to say it can't take some really nice images. Whether you're happy really depends on your expectations for your images.

I see the new maxi output is quoted in GN, while the circular tube strobes have power listed in Ws. I would be interested to know how the maxi compares to the output of the circular tube strobes.

I think there are a number of issues you are facing - first adapted lenses and macro are always going to be a problem, the second a lot of zooms are slow on the long end and less light means AF suffers generally. Plus kit lenses generally don't have the best AF a company has to offer. Extension tubes may work, but you are back to the same situation you have when using a diopter, the focal range is relatively limited. Adapters like the Nikon FTZ or Canon ef-R are probably less impacted and there are a number of EF or F mount short macros that may work well enough? Generally short primes are pretty snappy to focus. On my OM-1 the 30mm Panasonic is noticably snappier than the 60mm macro up to at least 0.5x. An extension tube on a fast prime may work as well??? Seems like there's compromises to be made, perhaps one is to accept taking video in a crop mode with a lens that is fast to AF but not so good at min focus or perhaps a lens that only reaches 0.5x? The difficulty in focusing seems to go as you increase magnification, particularly beyond 0.5x. I'm wondering if the Canon STM lenses that go to 0.5x might do well enough for you under this scenario? Just some random thoughts.

Depends on the lens in question, I know the Nauticam 180mm dome has a max angle of view of a 16mm lens with exit pupil positioned properly as the dome is not a full hemisphere. This means the exit pupil needs to sit forward of the optimum spot to avoid vignetting. The marelux has a slightly bigger throat which helps with positioning but not sure if it can be placed 100% correct. The Sigma lens you mention has a long minimum focus distance (28cm) while some newer lenses focus a lot closer like the 17-28 f2.8 tamron which focuses down to 19cm. This means it works well in smaller ports. There are lots of posts on the forum discussing that the new Sony wide zooms and the Tamron 17-28 among others will work well in a 180mm dome. I'm sure some will chime in with direct experience. I don't recall the Lens you currently have being among them. You could buy the 17-28 tamron and the 180mm port for less than the price of the 230mm port alone and get a smaller lighter package that is easier to travel with. Probably the more important question though is if a 14-17mm rectilinear wide lens is the right lens for what you want to shoot. Fisheyes are very popular for reef scenics and wet optics with the WWL are popular for CFWA and make for a compact easy to shoot and flexible setup.

It depends on how much buoyancy you'll be adding. In general you want the buoyancy components up high as they will want to turn to be there anyway even if the rig is overall neutral and the classic way to do this is buoyancy on the strobe arms. But if the buoyancy you add is too high you'll have a significant torque trying to prevent you from rotating the camera to point up. I think something 500-600 gr of buoyancy on the arms is fine, i have this on my regular rig and I don't notice the torque. On my newer setup using the Canon 8-15 on the OM-1 to get neutral I needed 2.2 kg of buoyancy and tried it with two 670 gr arms and two 210 gr arms and twisting it was quite difficult and I ended up removing the two 210 gr arms and dived it about 450gr negative. The reason for the torque is twofold - the amount of buoyancy and the arms being quite long it was placed a long way from the centre of mass so a strong lever. I am thinking of adding about 400 gr of buoyancy to the base plate. So just weigh your rig on a luggage scale in water and come back for more specific suggestions. What to do will depend on how much buoyancy you need to get close to neutral

You don't need an app to do that for you, just process a copy and copy it in as a new layer and mask it, simple enough to do in Photoshop.

Thanks Dave, The point is it makes comparing the fields you get from various lenses easier, particularly if you are comparing a rectilinear to a fisheye where the focal length is not a good guide at all. The purpose of providing a field of view is to help determine what sized objects you can fit within that field. Generally what you can fit is defined by the width of the long axis - you don't frame subjects diagonally in general. The issue you have is that the the barrel distortion of the fisheye and WWL is not linear, the degrees of field covered per mm of sensor increases as you get further from the sensor - the corners are stretched. This means that as you zoom in you get narrower fields than you might expect. The example I provided above of an 8-15 lens on m43 , from looking at focal lengths it seems like it is a 2x zoom lens, but it's actually like a 6 -28mm lens or a 4x zoom and replaces a fisheye and a 7-14 rectilinear in horizontal field coverage. Back to the original question, the 10-17 was very popular because it zoomed from a fisheye all the way to a 22mm rectilinear lens, about a 3.5x zoom ratio based on horizontal field. The only full frame match for that lens currently is an FCP which is an expensive, heavy option. The WWL-C has a similar 3x zoom range but shifted to the long end and missing the fisheye end. AN 8-15 with an added 1.4x gives about a 2.5x zoom ratio but lacks the reach of the WWL-C and Tokina 10-17. The other factor with the fisheye is the barrel distortion which brings your subject forward in the frame - it appears bigger and fatter - so for reef scenics it's really unbeatable. SO the choice to replace a Tokina 10-17 is if you mostly used the 10-14 range of that lens, an 8-15 with a 1.4x will replace that very well, but if you were mostly using the long end of the 10-17 the the WWL-C with 24-50 is potentially a better choice. If you do both reef scenics and CFWA then you might want both.

Dave, I'd appreciate it if you could explain why it is an issue to compare lenses this way rather than just throwing insults. The diagonal field of a lens is just a convenient way to compare with a single data point but doesn't give the full picture.

No I have the correct data, I am quoting horizontal fields of view that I calculated, not diagonals as I stated in the text. I find this much better to compare what size objects you can frame with a given system The 130° of the WWL and the 180° of a fisheye is mostly stretching of the corners. So a WWL has 130° diagonal field which seems like a 10mm rectilinear but the horizontal field is 106° which is closer to a 13-14mm rectilinear. Likewise the fisheye lenses are nominally 180° diagonal, but the horizontal field is about 140-144° which is something like a 6mm rectilinear if such a lens existed. See for example these two images, taken on m43 - the first is the 8-15 fisheye at 15mm, the second is the 7-14mm at 14mm. They basically frame the door the same way, the calculated fields on the long axis are 67 and 63°, while the diagonals are 88 and 78°. Using diagonals you'd think the 8-15 at 15mm had quite a bit wider view, but based on the long axis field of view they are very similar, the fisheye just includes more in the corners. which for the most part are unimportant for an image.

Your wide angle choice depends on how wide you want to go and how much reach you need. Here's fields of view of a few options compared to what you get from a Tokina 10-17. I am comparing by horizontal field of view rather than diagonal as this generally sets what you can fit within a frame. Fisheye corners stretch a lot more so than rectilinear of the WWL, but usually you don't have important subject matter there. Tokina 10-17 DX: Fisheye - 22.5mm rectilinear 144- 81° horizontal field Full frame: FCP with 24-50: Fisheye - 23mm rectilinear 140-97° WWL-C with 24-50: 14-43mm rectilinear 106 - 42° 8-15 plus 1.4x: Fisheye- 16mm rectilinear 144-97° The closet match to a Tokina 10-17 is the very pricey FCP. You already have the 8-15 so adding a 1.4x to that with a Nauticam 140mm dome would be a good solution if you don't need the full reach of the 10-17. I wouldn't consider the 14-28 for use in a dome, you need at least a 230mm and I recall seeing reports the 14-28 is not that great UW behind a dome.