Question about Inon 45 degree viewfinder

I shoot a Sony A6300 in a SeaFrogs Salted Line housing. I'm pretty happy with it, but one thing that grates on me is the difficulty of pulling off high-angle shots (shooting into the sun, etc), as well as getting close to the bottom - it really takes some contortions to see the LCD in those scenarios. The viewfinder unit that comes with the housing is next to useless (I tried it once, peering into a tiny tunnel with the EVF somewhere in the end, and promptly gave it up forever), but it is easily removable, leaving behind a 30mm wide opening that is approximately 10mm deep, with the viewfinder eyepiece some 20mm from its outer face (housing back).

I'm not going to invest several thousand dollars into a Nauticam/Aquatica/Sea & Sea housing and appropriate ports, not even a used one, but the possibility of adapting a $500 Inon viewfinder does sound tempting. On the face of it, it doesn't sound like too complex an issue - I just need to get a ring of appropriate dimensions with o-ring grooves machined and put it between the housing back and the viewfinder. However, it will only work if the viewfinder mount is smaller than 30mm wide, by a sufficient margin that the adapting ring will not be made of foil. There is also the matter of placing it at the appropriate distance from the camera's eyepiece. I can't find these dimensions on Inon's site - could anyone point me in the right direction?

A possible alternative would be to get an LCD magnifier hood and attach it to the little sun shade that mounts to the back of my housing, but it won't give me a 45-degree angle like a proper viewfinder. There's an AOI 90-degree LCD hood, but looking straight down for every horizontal shot might be too much, and I'm afraid that my head will bump into the float that I have across the top of my housing, holding a dive computer, as well as the focus light on the cold shoe.

18 hours ago, Barmaglot said:

I shoot a Sony A6300 in a SeaFrogs Salted Line housing. I'm pretty happy with it, but one thing that grates on me is the difficulty of pulling off high-angle shots (shooting into the sun, etc), as well as getting close to the bottom - it really takes some contortions to see the LCD in those scenarios. The viewfinder unit that comes with the housing is next to useless (I tried it once, peering into a tiny tunnel with the EVF somewhere in the end, and promptly gave it up forever), but it is easily removable, leaving behind a 30mm wide opening that is approximately 10mm deep, with the viewfinder eyepiece some 20mm from its outer face (housing back).

I'm not going to invest several thousand dollars into a Nauticam/Aquatica/Sea & Sea housing and appropriate ports, not even a used one, but the possibility of adapting a $500 Inon viewfinder does sound tempting. On the face of it, it doesn't sound like too complex an issue - I just need to get a ring of appropriate dimensions with o-ring grooves machined and put it between the housing back and the viewfinder. However, it will only work if the viewfinder mount is smaller than 30mm wide, by a sufficient margin that the adapting ring will not be made of foil. There is also the matter of placing it at the appropriate distance from the camera's eyepiece. I can't find these dimensions on Inon's site - could anyone point me in the right direction?

A possible alternative would be to get an LCD magnifier hood and attach it to the little sun shade that mounts to the back of my housing, but it won't give me a 45-degree angle like a proper viewfinder. There's an AOI 90-degree LCD hood, but looking straight down for every horizontal shot might be too much, and I'm afraid that my head will bump into the float that I have across the top of my housing, holding a dive computer, as well as the focus light on the cold shoe.

 

How thick is the housing material at this point?  That may have an impact on the feasibility of the project.  Presumably the current viewfinder is sealed with an o-ring.  The Viewfinders themselves are likely similar sizes, Nauticam one has o-rings that are 27.6mm OD, so the ID of the opening is probably around 27 - 27.1mm ID or so, assuming 2% for squeeze.  You should be able to find guidelines for this via google.  So the walls would be 1.5mm thick which seems marginal - of course it's not the INON viewfinder.  It also needs to be just the right length so the retaining system for the viewfinder works.  It also needs to be quite smooth for the o-ring seating surface and appropriate chamfers to assist getting the o-rings in without damaging them. 

As to how close it needs to be - I would suggest another post requesting anyone using an INON 45° viewfinder to see what the spacing dimension is and also how it works with a Sony viewfinder

6 minutes ago, ChrisRoss said:

How thick is the housing material at this point? 

10mm, although there is a partial cutout making room for LCD screen hood:

11 minutes ago, ChrisRoss said:

Presumably the current viewfinder is sealed with an o-ring. 

Two of them actually; one face-sealing against the housing back, the other on the inside of the 30mm wide channel:

It's retained with a simple ring nut:

But owing to the LCD good right next to it, there's not a lot of free space surrounding it:

21 minutes ago, ChrisRoss said:

The Viewfinders themselves are likely similar sizes, Nauticam one has o-rings that are 27.6mm OD, so the ID of the opening is probably around 27 - 27.1mm ID or so, assuming 2% for squeeze.  You should be able to find guidelines for this via google.  So the walls would be 1.5mm thick which seems marginal - of course it's not the INON viewfinder. 

Thanks; 1.5mm should be okay with aluminium - there aren't any lateral loads being placed on this part. Inon actually makes a Nauticam-compatible model, so even if the Inon's own mounting ring is wider, I should be able to use that one.

28 minutes ago, ChrisRoss said:

It also needs to be just the right length so the retaining system for the viewfinder works.  It also needs to be quite smooth for the o-ring seating surface and appropriate chamfers to assist getting the o-rings in without damaging them. 

Measuring the pixels on the photo on Inon's specs page, it looks like it should be long enough to go through the 10mm back on my housing, and the tiny protruding screws can be accommodated by drilling equally tiny holes. Chamfers - yeah, but it doesn't look like all that complex of a part; just a ring with precise dimensions and a groove or two; I hope it shouldn't be too difficult to find a shop to machine it.

29 minutes ago, ChrisRoss said:

As to how close it needs to be - I would suggest another post requesting anyone using an INON 45° viewfinder to see what the spacing dimension is and also how it works with a Sony viewfinder

That's why I'm consulting the hive mind here

16 minutes ago, Barmaglot said:

10mm, although there is a partial cutout making room for LCD screen hood:

 

 

Two of them actually; one face-sealing against the housing back, the other on the inside of the 30mm wide channel:

 

It's retained with a simple ring nut:

 

But o.

Thanks; 1.5mm should be okay with aluminium - there aren't any lateral loads being placed on this part. Inon actually makes a Nauticam-compatible model, so even if the Inon's own mounting ring is wider, I should be able to use that one.

Measuring the pixels on the photo on Inon's specs page, it looks like it should be long enough to go through the 10mm back on my housing, and the tiny protruding screws can be accommodated by drilling equally tiny holes. Chamfers - yeah, but it doesn't look like all that complex of a part; just a ring with precise dimensions and a groove or two; I hope it shouldn't be too difficult to find a shop to machine it.

That's why I'm consulting the hive mind here

 

The Inside of the viewfinder adapter is smooth - the o-rings are on the viewfinder, so it's just hollow. The depth of the viewfinder adapter is set by the viewfinder itself it looks like maybe it's 15mm deep??.

You will need a groove in the face of the adapter - basically the same as the o-ring groove you have on your current eyepiece that seats against the outside of the housing.  This o-ring prevents water leaking in through the adapter.

You will need two cutouts in the top of the flange of the adapter to mate up with the two pins on the INON viewfinder.  This stops the viewfinder rotating in the adapter.  The rotation of the viewfinder is done within the viewfinder itself and includes the click stops - The pins also make sure it is facing up when clicked into position. 

Regarding the strength of the adapter tube it needs to resist bending force on the viewfinder from handling - it is probably OK but wouldn't want to go much thinner.  On the chamfer it's simple but you have to make sure it is done.  thickness of the adapter will also potentially impact how you retain the adapter/viewfinder as the nut on the end of the Inon viewfinder will press down on this surface and it may be a problem if too thin.

You need to retain the both adapter AND the viewfinder.  The viewfinder has two piston o-rings and can move in and out a little and still seal.  The adapter is only sealed by a face o-ring seal and CANNOT move in and out at all, otherwise the seal may be lost.  You don't have a lot of room there - you might be able to have the nut on the end of the Inon viewfinder retain both - but you would have to design it to do so.  The viewfinder retaining nut would need to bear against the housing back - NOT the adapter.  The simplest solution might be two nuts as you would need quite thin custom nut made and machined so that it wouldn't bear against the adapter - only the housing. 

6 minutes ago, ChrisRoss said:

The Inside of the viewfinder adapter is smooth - the o-rings are on the viewfinder, so it's just hollow. The depth of the viewfinder adapter is set by the viewfinder itself it looks like maybe it's 15mm deep??.

Something like that, yes. There is a little space (maybe about 5mm) left between the inner flange of the SeaFrogs viewfinder and the camera viewfinder eyepiece.

7 minutes ago, ChrisRoss said:

You will need a groove in the face of the adapter - basically the same as the o-ring groove you have on your current eyepiece that seats against the outside of the housing.  This o-ring prevents water leaking in through the adapter.

Good point; I thought about making it just a straight tube, but a mushroom-like flange on the outside holding an o-ring should make it safer.

8 minutes ago, ChrisRoss said:

You will need two cutouts in the top of the flange of the adapter to mate up with the two pins on the INON viewfinder.  This stops the viewfinder rotating in the adapter.  The rotation of the viewfinder is done within the viewfinder itself and includes the click stops - The pins also make sure it is facing up when clicked into position. 

I will probably need little pits for the pins in the housing itself as well; this will stop the adapter rotating within the housing back.

9 minutes ago, ChrisRoss said:

The adapter is only sealed by a face o-ring seal and CANNOT move in and out at all, otherwise the seal may be lost. 

I figure I will have a groove on the cylindrical portion of the adapter as well, for a second o-ring within the tunnel, same as the SeaFrogs viewfinder.

10 minutes ago, ChrisRoss said:

The simplest solution might be two nuts as you would need quite thin custom nut made and machined so that it wouldn't bear against the adapter - only the housing. 

Probably, yes - threading on the end of the adapter and a nut securing it to the housing, then the viewfinder protruding through and held with its own nut.

Also, while I'm at it - Inon vs Nauticam 45-degree viewfinders? I found this article, but it's from a decade ago, and both have been updated since then - but the price difference is much greater than it used to be, with Inon being available for just $450 through DiverVision, while Nauticam is over triple the price at $1379; a far cry from the 20% difference that Alex Mustard talks about.

3 hours ago, Barmaglot said:

 

Good point; I thought about making it just a straight tube, but a mushroom-like flange on the outside holding an o-ring should make it safer.

I will probably need little pits for the pins in the housing itself as well; this will stop the adapter rotating within the housing back.

I figure I will have a groove on the cylindrical portion of the adapter as well, for a second o-ring within the tunnel, same as the SeaFrogs viewfinder.

Probably, yes - threading on the end of the adapter and a nut securing it to the housing, then the viewfinder protruding through and held with its own nut.

In order,

not safer - essential, you have two seals to make.  The adapter needs to be sealed to the housing and the viewfinder sealed to the adapter.

Maybe not - the adapter will be like any sort of bulkhead plugs on a housing you tighten it down reasonably tight .  It will need the right sort of machining so that you don't over squash the o-ring - an exact copy of the viewfinder flange/O-ring groove would do it.

If the tube is 1.5mm thick I wouldn't suggest doing that you don't have the material thickness to lose.  Bulkhead plugs seal with just a a single o-ring.  I would make it a "bearing fit" in the hole in the housing - you can just and only just slide it in - that way it can't move laterally.

Yes, the nuts would be quite thin. 

@Barmaglot did you get any further with this? Looking to do a similar thing.

3 hours ago, Tutem said:

@Barmaglot did you get any further with this? Looking to do a similar thing.

I've put it on hold for a while, as I'm currently traveling - I'll be home in about a month, and then I'll pick it up again. I'm still curious about the diameter of Inon's X-2 mount, or any other viewfinder mounts that Inon makes it for - Aquatica, Ikelite, Anthis/Nexus, Sea & Sea, Patima - if any of them have a mount diameter smaller than Nauticam's 27mm, that would make creating an adapter easier.