Chris Ross

Need more details of what you are doing, what trigger, manual or TTL, are you using the booster, how many frames/sec you are trying etc?

Thanks for the update on the strobes, I also upgraded recently, however I got a set of Retra Pures before they were discontinued, which were lower powered but significantly cheaper. The biggest change I noticed was significantly less backscatter when using them with reduction rings for macro shots. By no means backscatter proof but immediately noticable compared to my old INON Z240s. Haven't done much wide angle with them as yet, but been pleased with light quality on what I've done so far.

So is this only when you started using it in very cold water or is it was working for a while in the very cold water but suddenly started dying? This may indicate a new battery could do better? Other than that you could try keeping the housing in a cooler with a hot water bottle until you hop in the river perhaps?

Your best bet is probably the newer battery, it could be you've lost a bit of capacity of your existing battery as well if it's a few years old. The USB bulkhead only helps if the camera allows battery charging in the camera, the 5D MkIV does have this option it seems?

I found a reference that states that a dome port gives increased depth of field in water compared to what you would get from the same lens in air. This is due to the object being compressed into a virtual image close to the dome. Whether the Ivanoff optics work from a virtual image I don't know, but I expect that it quite possibly could. They give an example of a 24mm lens at f8 imaging an object at 1m distance having 563mm DOF UW and 424mm in air. Here is the reference, scroll down to section 4. https://pmc.ncbi.nlm.nih.gov/articles/PMC4732081/ Without doing a detailed analysis, it's basically guesswork as to what is going on as the Ivanoff optic is neither a dome or a flat port. A flat port is limited to a field of 96° by Snell's law, but a 16mm lens has a field of view of about 106°. Odd things can happen with some optics UW, the Nauticam FCP for example seems to suffer from reduced depth of field based upon posts from users when it was first introduced.

Welcome aboard, I recall we have a few free diving photographers on the site. Type freediving into the search box and it brings up a lot of posts.

Not on a APS-C camera but I reported on using it with the Olympus 60mm macro (2x crop) recently: If it works well on m43 and full frame it stands to reason that it will work fine on APS-C. The 100 mm macro is 160 mm equivalent on the R7 while the 60mm macro on m43 is 120mm equivalent, so I would suggest even more of a case to use it on APS-C. The specs for the field of view and working distance /magnification on Canon APS-C is on the MFO-3 port chart: Google DocsMFO-3 2025-08-27.pdf

Great images captured must have been quite the experience.

I have no doubt it would work well in a dome, I would say though using it as macro lens is different to use in a dome where you are out in the 0.3x magnification and less with a working distance up near 70mm due to the dome where the AF of macro lenses generally picks up. I know what you mean about focusing on skinny things - transparent things give similar problems, seems like there are some things that the AF gets confused with. I encounter occasional things the AF doesn't play well with on my m43 setup.

I have the original Nauticam 45° which I used with the EM-1 MkII before moving it to my OM-1. The attachment is different between the MIL and DSLR versions, but the mounting can be swapped over to suit either a mirrorless or DSLR housing. As I recall the corners of the viewfinder were a little soft in the EM-1 MkII, while in the OM-1 they are softer still. The centre of the image is fine but reading to info in the corners is a little harder. The new versions are reported to be better in the corners. this approximates the view through the 45° on the OM-1 , ignore the vignetting as that's due to alignment issues with the lens and viewfinders. The blur in the corners is halfway between the far left and right side of the info bar at the bottom of the viewfinder image. It's difficult to get everything lined up using a camera lens compared to just placing your at the viewfinder. The EM-1 MkII viewfinder view is a bit better than this but the corners are still a little blurry.

The acrylic dome would probably be easier for splits as it is floaty compared to the glass, but using UW, it will want to try to twist up. Of course it is more prone to scratches.

Yes macro is easier without a wet lens. The system only focuses in quite a narrow range with the diopter. The 50mm has a different issue in that it 1:1 magnification where it covers 36 x 24mm is achieved at about 10-15mm from the port making it difficult to use and lighting is difficult, in practice it probably only easily achieves the sort of magnification you currently get with your current setup. What I was trying to say with ikelite is they will allow you use your lenses UW and will work, but there are various compromises. They have limited flat ports available for example they offer the same port for the 3 different macro lenses in m43 which are different lengths which means the shorter lenses are set back behind the port. What this means is that closest focus for those lenses is inside the port meaning it restricts the magnification you can achieve. They don't tell you this though. you also need to look at the fine print for each lens in the port chart to see if there are any restrictions. In particular for the DLM system there are many port options that won't allow zoom, they rely upon a 6" port with a zoom knob as there is no zoom control on the housing. They also don't have a 4" dome for a fisheye lens. Don't get me wrong amny people use their housings, but there are more compromises. On wet lenses, they rely on having a well fitted flat port and if the front element is too far back in the port you get vignetting. the lens in question might work behind the port by itself just fine but will vignette in combination with the wet lens. The other consideration with Ikelite is that it is only setup for wired triggering, which means maintaining the o-rings on trigger cables. Something I'd prefer not to do, The website only mentions using a manual flash bulkhead. You might be able to use the UWT external flash trigger to trigger with fibre optics. If you are determined to go with the A7CII maybe consider the new AOI housing, has built in vacuum and flash trigger with Sony TTL support or manual. based 100% around the Sony 28-60 it seems. You would use it like the RX-100 and rely on wet macro and wide lenses. You could use the +10 diopter you have and possibly buy one of the AOI wet wide lenses.

regarding the macro you can fill the frame with a 1:1 macro lens be it the 90mm or 50mm with a smaller subject than you can do with the RX-100V and your +10. The Rx with +10 diopter gets about 0.7x while you get 1x magnification. So you don't actually need the diopter till you want to go to significantly smaller subjects. The ikelite does things differently the ports will get your lenses UW, but may have certain compromises with a lot of lenses. On the subject of wet lenses it's a bit different to the RX100 and the way it works, Macro with a proper macro lens is "better" than sticking on a wet lens. The wet lenses only focus in a certain range, but with a macro lens you focus all the way from infinity max magnification. But having do everything doesn't really work with bigger cameras, but it's better at both macro and wide than a camera you need to use with wet lenses. Something that goes close is something like a wet wide lens which goes from about as wide as a 14mm lens through to about at 35mm lens which focuses up to glass and can fill the frame with subjects around 50-100mm in size for CFWA. It's nice if you can use the same setup above and below water, but it may be limiting, but if you are talking about space and volume savings then the small m43 lenses tick all the boxes. as the lenses and their ports are all smaller and the range suitable for UW is quite complete. The only thing maybe slightly lacking is for astro, but I've been reasonably happy using my setup for fixed tripod work. I went with Olympus UW and was using Canon above, but I basically shifted everything across, long lenses for birds, wide angle landscape, land based macro and the Canon gear hardly gets a look in these days,

Quite a few things to consider, first thing to think about is the budget you have in mind. Secondly the camera body may be small but full frame lenses are large and expensive and the ports to house them are larger and more expensive. Then there is the matter of ports, wide angle rectilinear lenses demand large ports. You mention the 14mm f2.8 lens, in Ikelite their basic recommendation is to use it in a 6"port which seems a bit on the small side for a 14mm lens and the corners will likely be soft. Ikelite also mentions that the DLM port system used with the A7C II housing can't use the larger lenses that other Sony cameras can in their system. 14mm rectilinears are not that popular UW and fisheyes and wet optics like the WWL are used much more often. Fisheyes are very useful UW as there are few straight lines except perhaps wrecks and for the most part you could never tell a fisheye was used. To demonstrate the size difference here is a a comparison of the A7CII with 90mm macro and an OM system OM5 with a 45mm lens, they both have the same reach and both achieve 1:1, however the whole package is a lot smaller with the m43 macro lens which will also fill the frame with an object half the size of the full frame lens and arguably you wouldn't need wet lenses: https://cameradecision.com/size-comparison/7en0_idfy-FtDC_KsMO-t For wide angle UW I'd suggest considering a fisheye. For Sony that means a converted Canon 8-15 fisheye, while for m43 you could use either the Panasonic or Olympus fisheye, which has a number of advantages, besides being small and light it works very well in a 4"dome for reef scenics and CFWA and will focus right down to the dome surface. Here's a photo of an EM-5MkII with a Panasonic fisheye lens attached: The EM-5 II is the same size as the current OM system OM-5. So the summary is that camera body size is a very small part of the overall weight and bulk for travel of an UW system, the lens size, weight and price is much lower with m43 equipment and the ports to house them are significantly smaller. The sensors in m43 are a good step up in quality compared to the RX100. Don't get me wrong a number of people are happy using the A7C cameras, but they don't provide the compactness you'd expect based upon their camera body size. On the 50mm macro, you could achieve 1:1 magnification with that lens. The wet lens diopters you have work by allowing you to focus closer, however the Sony 50mm extends to focus close making it less suitable for diopters and the working distance at 1:1 magnification is only 18mm from the front element, so likely about 10-12mm from the port glass. adding a diopter won't allow you to focus any closer. In fact with 18mm working distance, lighting something at 1:1 magnification will prove challenging due to shadowing from the port.

Particularly with the WWL, at the wide end you could open up to f5.6 for a full stop more flash in your photos if you needed it and I would think shooting in the blue that the the Olympus fisheye would also work well at f5.6. The only problem you might run into is the max flash sync speed if you are in shallow water and pointing up where you might want to stop down some more to get the water darker. If the S220 is near as powerful as the YS-D3 you should have no problem, the S220 at 19.6GN vs the YS-D3 at 25 with diffusers is about 0.7 stops difference in power. It seems that the S220 is at least as powerful as the old INON Z240 and some years back people wouldn't have hesitated to use the Z240 for wide angle pelagics, same with the YS-D3, no one would hesitate to use it for wide angle work on a full frame camera at f11-13 range I don't think. Remember these are measured GN by @DreiFish he also measured the HF-1 at GN 31 with diffuser. that is 1.3 stops more power than the S-220 as measured under constant conditions, which is equivalent to opening up from f13 to f8. The thing to remember is the S22- is quite powerful - to get 1 stop more power you need to double the output and that only allows you to stop down one stop. On the m43 camera you don't need to stop down to F11-16 and in practice f8 works just fine even for CFWA. By shooting at f8 you have already recovered the one stop lost by using the S-220 instead of the YS-D3 and if you need faster recycle and you can open up a little with the lenses you propose to use. The last point is that lighting up a whole whale shark is very challenging due to distance it is away, the best you hope for is give it a kiss of light as you are going to be 2-3m away probably at best.