Chris Ross

I would ask what you are missing out on with your current system , cropability is the only one that seems to stand out to me. Having said that I get plenty of perfectly usable images with up to 50% cropping out of the Olympus. I have used the EM-1 MkII for quite some time and now I'm using the OM-1 initially on land and now have housed it underwater. I've found the AF to be very good on both cameras, but the OM-1 is certainly a step up in AF capability. For example at high magnification on the 90mm macro it would lock focus where the EM-1 MkII could not, probably pointing to improved low light focus capability. But it seems AF is not a limiting factor with the EM-1 MkII for your uses? I'm not sure I get your argument on this item though: Field of view is field of view, you just need to have the same equivalent focal length on both systems, to get the same reach and field and ability to frame comfortably. If 80mm full frame equivalent is enough for you the 12-40 olympus lens is very sharp right from wide open and focus is extremely snappy, it just locks on and as a bonus will focus very close allowing about 0.3x focusing right on the dome. Macro lenses as a rule will generally be slower if for no other reason that they have a very wide focal range to work through. the 12-45 f4 is a slightly smaller package which has similar to the 12-40. Regarding resolution, underwater shooting through a significant amount of water is a great leveller. What ultimately sets your resolution is pixel size and the OM-1 20MP sensor has 3.3 micron pixels while the 61MP Sony has 3.6 micron pixels, so pretty much a wash for pixel size with a small advantage to the m43 sensor. The other consideration is depth of field the same fish comfortably framed the same way on full frame has less depth of field than a m43 frame. You can shoot m43 at f8 and get the same depth of field as full frame at f16. This also means with the same pixel size you are deeper into diffraction in general on full frame. In general you will be shooing with a wider f stop on m43 and this means that you need less strobe power which is a consideration if you are backing off and using longer focal lengths for skittish fish meaning faster recycle times. Depth of field may be important for example in trying to do ray counts on a small fish that refuses to let you get parallel to it. Diffraction starts at f7.1 on a 61 MP sensor but you do need to stop down quite a bit more before it starts to impact resolution the difference is you could probably shoot at f5.6/8 on m43 all the time and be effectively diffraction free while full frame you might be f11 at minimum. This is probably more of a leveller between the formats than a clear advantage for m43. To me this means why go to the expense of FF?

It is quite possible to "vacuum" a housing together, most housings you would need to open it in flight and close it up again. Housing clamps only need to be tight enough to pull down the housing to make an initial seal and the clamps may or may not be able to resist a small movement in the back of the housing due to internal pressure. UW they rely on water pressure to keep them closed tight. To explain a clamshell style housing if you fly with it closed with the clamps in place the air inside tries to push it open at altitude but the clamp stops it opening, it might move a bit but, not enough to unseat the o-ring. But a housing with a flat back and a surface o-ring like an ikelite even if clamped only needs to lift the back a tiny amount to lose o-ring contact and lose the air inside, but when the plane lands external air pressure starts to push the back closed and you are left with a vacuum inside. But if you have a vacuum valve you can release the vacuum and there is no problem. It's also of course only a potential problem if you fly with a port mounted to the housing. For packing I often have the plastic cover on front rather than a port and I can do what I like as the housing won't hold a vacuum - o-ring or no o-ring.

Interesting post, it would be an ideal method for housing manufacturers I would think - all they would have to do is half fill their test tanks to try it out.

Don't forget UW red light is scattered much faster, the light should be a little dimmer - try both settings.

I've used a red focus light on land with both Olympus and Canon and it seems to work quite well, that however is shooting fairly distant subjects and there is contrast between subject matter and the black backgrounds. Have you tried reducing the brightness either on the light or taking it further away - one possibility is it is saturating the chip and as it's all red light it can't find anything to focus on.

OK Thanks, if you have google drive it's a good method you just have to set permissions to anyone with the link.

I haven't done the Murex deal but I know people doing it in a month or two. I went to Diver's lodge Lembeh when I did Lembeh a few years back and I would highly recommend them. They have as standard 2 divers one guide, though they now have a private boat scheme which may add to the costs if you are travelling alone. They will also pick you up of drop you off at other resorts. An additional consideration is they will dive the far side of Lembeh Island at the right time of year which has coral sites as opposed to muck sites being at the SW end of the island the trip around to coral sites is relatively short. In addition, food is good, accommodation comfortable and pricing reasonable. https://www.diverslodgelembeh.com/ also see their FAQ page about timing. I was there in November just as the wet season was kicking off so it was drizzling a bit. Some critters are seasonal for example Ornate ghost pipefish are most sighted June-October. This guide may be useful: https://critters.lembehresort.com/ornate_ghostpipefish_solenostomus_paradoxus_c62.html Just type in critters you are interested in and it says where they are found and any seasonality.

The toslink connectors themselves will fit in a Sea&Sea standard socket if you shave the corners off the square connector that surrounds the round metal piece which holds the fibre - just trim carefully with a Stanley knife. I've purchased a toslink cable in the past to get me out of trouble.

Interesting - if I had the RAW file I'd like to have a go using my method using Capture One.

Min focus is about 20mm from the port glass. I have the Panasonic 30mm f2.8 macro which I use occasionally UW. I find that max practical magnification to be about 0.5x for UW use. The Panasonic lens has very snappy focus and is better than the 60mm macro in that regard.

The histogram on the SONY page looks quiet different, the blues and greens have peaks in similar spots to lightroom but the reds have a peak much lower. I'm not sure how you could achieve that with moving the blue-Yellow colour temperature slider and Green-Magenta Tint slider alone. I use a different method using levels and it seems to work quite well as long as the image is well exposed and has enough red channel to play with.

Thanks for posting. I would think that the grinding is only required for 5 series camera - OM-5 EM-5 mkIII etc. They have the lens mount very low on the camera body, while the lens mount sits higher up the body of the OM-1. EM-1 MkII etc. so the Metabones adapter might clear the tray on those models.

Salt water is not a problem for glass, you dive in it after all. As this water evaporates the salts become more concentrated and I expect the pH will also increase and eventually reach the point where the glass can be etched. This is a slow process and repeated evaporation events are needed before it becomes obviously visible. A plastic cap could work but only if it is tight fitting to prevent the water that evaporates from escaping once humidity reaches 100% under the cap no more evaporation. Most improvised caps won't be able to seal well enough to be useful. Glass corrosion or etching can be removed but requires much more effort. Glass domes will be ground and polished to reach the surface finish that they require - same as glass lens elements. People report using cerium oxide for this and this is a common polishing agent for optical glass, however it requires much more elbow grease to have any impact. A neoprene cover should be adequate. If the weather is hot re-dunk it occasionally or add a splash of water from a drink bottle.

Probably little you could do about it unless you could get the lens to report the focal length with the WWL. That's probably something around a 14mm rectilinear frame (full frame equivalent) on the horizontal axis. You could probably only tell by trying it and see how it handled.

A neoprene port cover significantly slows drying of the port surface and this is a significant benefit. The article is wrong because it is incomplete, the port cover needs to dry out to cause the damage, but this is not going to happen on a day boat unless you leave your housing in the sun. If you are going to apply your port cover you need to be sure to keep the neoprene wet. My experience shows when shore diving around home I apply the port cover coming out of the water and leave it on between dives and the transport it home, the cover is still wet several hours later. The port cover is soaking wet as it has been in the water with me. Leaving a port uncovered to sit between dives the surface will dry out and the drying out is what causes the damage as the salt become more and more concentrated as the water evaporates. You also do not want to have fresh water dry on the port - when drying it blow off excess water and wipe/polish with a clean micro fibre cloth. I would not apply a dry port cover to a port when getting out of the water as it will absorb water and the dome surface can dry out. The port cover is removed as I pop the housing into fresh water to soak and it is also rinsed out then soaked to remove salt.

When you want to embed images, choose the files and with your cursor where you want the image, hover over the thumbnail and you will see the link "insert"appear click that and it will insert where you had you cursor. I think you then delete the images at the bottom. You have to do it while it is still editable, the abailty to edit a post has a time limit.

Thanks for supplying the parts list. Looks like a straight forward solution. For information of others looking to copy this setup, The gear is SKU 3546 is "EF 8-15mm f/4L Fisheye USM + Adattatore Olympus (EM5)" The 40 mm extension SKU 2548 is the 40mm extension with zoom mechanism. Let us know how it fits together once you get all the parts.

It's not just the minimum focus distance it's also the length of the lens and the 8-25 gets longer when expanded for use. The formula is 230mm - flange distance - lens length = working distance. The lens is 88.5mm long and expands by 28mm when in use. So working distance = 230-20-88.5-28 = 93.5mm while the radius of a 6.5" hemisphere is 83mm. So it's going to be close to focusing on the dome depending on where the entrance pupil is located. The partial domes I suspect won't allow you to place the entrance pupil at the centre of curvature. Even if it doesn't quite focus on the dome it doesn't mean its suddenly unusable.

I'm not sure that anyone has come up with the parts list to do this with Isotta. To adapt the 8-15 you need the Metabones T smart adapter and then you need to figure out the appropriate extension to use with your chosen Isotta dome. The other thing you need is a custom zoom gear. On Nauticam with their N85 ports this needs to mate up with the zoom knob on the N85-N120 port adapter. This requires a 3D printed adapter for the zoom gear to get it to mesh with the gear on the zoom knob, on that system the zoom gear needs to be placed 5mm lower on the lens. The small diameter of the N85 port means that there is no possibility to use a standard zoom gear with the housing zoom control. On Isotta there is only one B102 extension ring which a zoom knob. This may or may not be appropriate to use with the proposed setup. However the Isotta ports are a lot bigger than Nauticam n85 and this may allow the use of a custom zoom gear and use the housing zoom control. I see on Isottas website they have a lot of gears for adapted Canon 8-15 lenses and one of these might do the job, the descriptions on their website are not that clear. There is one labelled as Olympus adapter but there is nothing to clarify that, you would need to ask Isotta. If they have made an adapter they can probably also advise what extension you need.

I would add that Isotta list 3 6"domes, the polycarbonate one is a partial hemisphere while one of the glass models is a part hemisphere and the other a full hemisphere. To get the best out of the fisheye you would want the full hemisphere, to allow you to get the entrance pupil somewhere near the dome centre of curvature. . It of course will still produce quiet OK images with the part hemisphere domes, you just have to have a look at the Ikelite compact travel dome they sell for CFWA work with full frame fisheyes. https://www.ikelite.com/blogs/buying-guides/when-to-use-a-compact-8-dome-port-underwater The pics they post look OK at that scale and many people would be happy with them , even though the dome centre of curvature is well down inside the dome extension and possibly 100mm behind the dome surface. Fisheyes seem to be less sensitive to this issue at least for edge sharpness. However if you want the very best the camera can deliver you would want to get the centre of curvature better positioned. On the issue of a 61MP image being more demanding yes it's true the greater resolution will show up lens errors more readily, but only if you view them in a manner that allows you to see that. If for example you thought the corners were OK on a 30 MP image, you still have 30 MP grade resolution (as set by 30MP chip pixel size) in the corners on a 61 MP image. I'd also question if you achieve 61 MP resolution shooting at f11-13 range, shooting through water and also contending with the air-water interface and all the issues that brings with it.

I am converting to using a Canon 8-15 adapted on a metabones along with the 140mm dome from Nauticam and it covers the range from an 8mm fisheye all the way through the 14mm end of a 7-14 so I don't need a rectilinear for reach, the only reason to do so would be I wanted straight lines for wrecks or similar purposes. I agree the 6"dome is a bit too small for for the 7-14 lens, sure it will work but the corners will be a quite soft and as you have the entrance pupil forward of the optimal point you introduce some distortion. You could look at the Olympus 8-25 instead of the 7-14 as it will be less demanding on the dome. Isotta offers a 6.5"crystal dome which is a much closer to a full hemisphere and allows you to position your lenses correctly. Being in Isotta you could struggle to replicate the 8-15 rig I use so it may be simpler to stick with your Olympus fisheye. Sounds like you already have the Isotta 4.5"dome and assuming it's the fisheye dome (B102-H47) that would be the ideal setup to use with Olympus fisheye. If you were to buy the 6.5"crystal dome (full hemisphere model) you could probably use that for both the 8mm fisheye and the 8-25mm recognising that the corners won't be at their best with the 8mm end of the 8-25mm.

I think the response perhaps need to be qualified to confirm the Depth of field is less at the same framing - meaning the subject is the same size in the frame. You will shoot closer with the fisheye compared to the WACP to get the main subject the same size but for regular lenses on land this will result in the same amount of depth of field with varying background coverage. What also happens on land is the blurring of the background detail comes in faster with longer focal lengths even though the actual depth of field is the same. Again with regular lenses depth of field is purely a function of magnification and f-stop. I think if indeed the FCP reduces depth of field it probably indicates something about how it works. I have read that dome ports actually increase depth of field - perhaps the FCP works like a lens in air and gets the depth of field that a lens in air achieves?

Typically the firmware upgrade is to deal with new camera bodies and lenses which often won't work with the old firmware. Metabones also has upgradable firmware. It seems the Metabones works with more lenses, but if the lens/camera is on the compatibility chart you are generally OK. I picked up my Metabones used also. Also Metabones will respond to email support questions. Also you just want the T Smart adapter model, the Speed booster ultra includes a 0.71x optical element which you might use to for example on a 10-17 with a m43 camera to get full 180° coverage at the wide end. Not needed with the 10-17 on Sony APS-C. Read through the notes on the EF-Sony lens adapter here: https://www.metabones.com/products/details/MB-EF-E-BT5

In domes the lens needs to focus on the virtual image about 3 dome radii from the dome surface so quite close, pre-setting focus can work on land, not so much underwater. Also typically you want to work very close with a fisheye, almost touching the subject in many cases and precise focus then becomes critical.

Yes that should be fine as long as you can use the zoom control knob on the housing with that lens.