Does anyone have the distance for the A7 camera flange to the port seat on the NA-A7 housing.

I am trying to convert the NA-A7 Nikonos adapter for the Fuji Nauticam housing.

I need to figure how much I need to reduce the flange distance of the Adaprter.

The lens work but I need to reduce the flange distance to get it to focus at infinity.

It will focus with the adapter but acts like an extension. 

This does not make much sense as the lens is already 20mm so you would be looking at best at 30mm?

I am assuming APSC as medium would vignette

 

The difference between the Fuji Mount and the Sony E is .3mm. 18 on the Sony, 17.7 on Fuji.  Nikonos focal flange is 28mm.

If the adapter to sensor distance is the same from the Sony to the Fuji, I would have to shave .3mm. I do not have the Sony camera and housing available to measure. Reluctant to put a mic directly on the Fuji  sensor to measure.

3 minutes ago, Tobyone said:

The difference between the Fuji Mount and the Sony E is .3mm. 18 on the Sony, 17.7 on Fuji.  Nikonos focal flange is 28mm.

If the adapter to sensor distance is the same from the Sony to the Fuji, I would have to shave .3mm. I do not have the Sony camera and housing available to measure. Reluctant to put a mic directly on the Fuji  sensor to measure.

The adapter doesn’t touch the sensor it is just a piece of rubber that goes on the mount 

the nikonos 15mm is indeed 20mm

with apsc crop this is 30mm

you can shoot many lenses that work well at 30mm

On my Nauticam A7II housing the distance is 25.97mm. 

 

However, it should be noted that in at least some cases the Nauticam adapter does not provide infinity focus with some of the Nikonos lenses. It could be that the Nauticam adapter is a tad too thick or that some of the Nauticam housings hold the camera a tad too far from the port mount. Either way some users have had to modify their housings to bring the camera a tad closer to the adapter in order to achieve infinity focus. So to ensure success the first time around you might make your adapter slightly thinner (perhaps 0.5mm) than the Nauticam dimensions indicate. Here's a link to a wetpixel thread on the subject. 

Edited April 30, 20242 yr by Isaac Szabo

15 hours ago, Isaac Szabo said:

On my Nauticam A7II housing the distance is 25.97mm. 

 

However, it should be noted that in at least some cases the Nauticam adapter does not provide infinity focus with some of the Nikonos lenses. It could be that the Nauticam adapter is a tad too thick or that some of the Nauticam housings hold the camera a tad too far from the port mount. Either way some users have had to modify their housings to bring the camera a tad closer to the adapter in order to achieve infinity focus. So to ensure success the first time around you might make your adapter slightly thinner (perhaps 0.5mm) than the Nauticam dimensions indicate. Here's a link to a wetpixel thread on the subject. 

Thanks Issac,

I will  do some calculations and see if I can match the two cameras sensor distances

Where the camera flange sits inside the housing was changed going from the a7 to the a7ii (and newer).

I would suggest looking at both port charts and taking into account the difference on top of Isaac’s measurements.

12 hours ago, Robin.snapshots said:

Where the camera flange sits inside the housing was changed going from the a7 to the a7ii (and newer).

I would suggest looking at both port charts and taking into account the difference on top of Isaac’s measurements.

The new A7III and post are at 27mm

this is housing to mount 

the sensor is 18mm below

to make it work you would need the two deltas to compare

again what would anyone do with 30mm equivalent is a mystery to me..

Edited May 2, 20242 yr by Interceptor121

I measured the Nikonos 2 flange which is 32.18 mm.from the lens mount base to the film plate. Being careful not to push the spring plate tensioners back. I measured the distance from the mounted Nikonos adapter to the Fuji XT-3 front of sensor protection glass(There is no bayer filter in Fuji) in the Nautical housing. The distance was 31mm. I have yet to get a depth of this glass to the sensor. Could be .5-2 mm in thickness. So it look like I can shave 1.5 mm and get the lens to focus near infinity.I will test by sliding back the camera on the plate in the housing top side. I have an 80 mm Nikonos Lens to test focus. Before I start removing metal form the adapter.

I made some adapters to test Nikonos lenses on Sony mirrorless 3-4 years ago. It's hard for me to recall all the details, but looking back at some of my notes, I think the adapter thickness I settled on was around 14-15mm. Sony flange distance is 18mm, which means my Nikonos flange distance was around 32-33mm, which is very close to your 32.18mm measurement. 

 

The X-T3 has 2 filters in front of the sensor which together total around 2mm. Below that is the sensor cover glass of perhaps 1mm (just a guess) and a small gap until the photosites. So I'd guess the total distance from the outermost glass to the photosites is more than 3mm, but it's probably not going to be possible to get the exact number since measuring the cover glass thickness and the gap underneath would require destroying the sensor. 

 

Rather than measure from the mounted Nikonos adapter to the outermost sensor filter, I would recommend measuring from the mounted Nikonos adapter to the camera's lens mount. Then add to that the camera's flange distance of 17.7mm and see how far off it is from 32.18mm. I think that should give you a pretty good idea of how much you need to remove from the adapter. It does sound like it will probably be around 1.5-2mm. 

 

How are you going to remove thickness from the Nauticam adapter? Can you just do it in steps (perhaps 0.5mm) and test each time until you achieve infinity focus?

After all the calculations, especially considering the glass in front of sensor, I think I am abandoning this project. I would probably have to machine at least 3 mm off to get close to infinity focus, leaving a too thin of a lip. Also considering the Fuji crop factor,I would not be getting the moderate(underwater)wide angle option the 15mm presents.  I will just use for macro with the 80mm and maybe see how the 15 does with closeups.

Thanks for everyones input.

Edited May 5, 20242 yr by Tobyone

Hello Tobyone,

I'm curious to know how the tests went?
I am interested in this topic, since I also own a Fuji X-t3 / Nauticam equipment, and I may have access to some Nikonos optics.

Any feedback regarding the quality of the files obtained and the ease of use of the lenses underwater would be wellcome.

All the best.

Apologies for beating on an old, dead house but since I am in the research phase on everyhing Nikonos and particularly the Nik 15, I came across this post and wanted to help settle the flange distance debate;)

This will get nerdy, hang tight if you're into that kinda stuff;)

History...
Let's start here:

On 5/1/2024 at 4:10 AM, Tobyone said:

Nikonos focal flange is 28mm.

[...]

So, @Tobyone quoted the (infamous) 28mm which makes sense as it's been popping up online as far back as 2010, it seems. We may even have an old post on Wetpixels to blame for it, but I can't find it right now.

However, I did find a 2010 reference from another forum:

No harm done as Toby soon realized that 28mm didn't make sense. So, he checked himself:

On 5/4/2024 at 2:55 AM, Tobyone said:

I measured the Nikonos 2 flange which is 32.18 mm.from the lens mount base to the film plate. Being careful not to push the spring plate tensioners back. [...]

Furthermore, @Isaac Szabo weighed in with a similar distance:

On 5/4/2024 at 5:02 PM, Isaac Szabo said:

I made some adapters to test Nikonos lenses on Sony mirrorless 3-4 years ago. It's hard for me to recall all the details, but looking back at some of my notes, I think the adapter thickness I settled on was around 14-15mm. Sony flange distance is 18mm, which means my Nikonos flange distance was around 32-33mm, which is very close to your 32.18mm measurement. [...]

And I just redid Toby's simple caliper measurement on a Nik V of mine. I got readings between 32.3-32.4mm so maybe pressing a bit more on the film pressure plate, but again, we are in the same ball park. (I don't have a proper height gauge but will try again more carefully in a few days).

I also found this old post:

I don't agree with him accounting for film thickness as without any film loaded, the pressure plate should be sitting right up against the film plane. And if, pretty big if, he was to account for it, the normal number used for film thickness is 0.15mm, not 0.35mm. So, he would be at 32.2mm - for practical purposes identical to Toby's 32.18mm.

Anyhow, it's one more data point and if we don't account for film thickness it's one that's almost perfectly in line with mine. (I was at 32.3-32.4mm)

So, I think we should call bull on the 28mm and never mention it again;).
The real number is indeed 32-32.35mm. (I think...)

A New Standard?
Now, here's where it gets really nerdy. We may all have been talking about the "wrong" measurement. If we look carefully at this cut through of a Nikonos, we see that the lens doesn't actually rest on that flat face (the one held in place with the three screws) but rather on the slimmer front area of the "walls". In other words, that alu insert that the Nikonos bodies have, we are locating on the very front of it, not the face a bit deeper.

You can see there's a gap between that flange face we have all been referencing because the lens actually rests on the front of that "wall". I estimate the gap to be around 0.25mm.

So, maybe the real Flange Distance for Nikonos should be called 39-39.35mm and not 32ish mm. Now, that's more a question of definition.
You can use which ever reference point you want as long as you don't use 28mm anything;)

Edited October 5Oct 5 by GeckoSub

Sorry, I was Part Wrong - More Confusion Ahead...
The following is probably only interesting for anyone wanting to make their own adapters or aiming to rehouse these lenses:

I always knew the Nikonos bayonet was spring loaded. You can pull on a lens and pull it away from the camera body by a few mm or even see a heavier lens sagging a bit on land. I always assumed that the spring mech was located in the body but just today, I realized it's actually in the lenses. Which kinda messes a bit with trying to settle the "debate" on a flange distance standard, haha.

I made a bit of a simplified CAD drawing of a Nik 35mm to show what's at play here:

The whole optical block is what's spring loaded and can move in and out. When at rest, when the lens is not mounted, it's pulled tightly against the "front lens body" and it really seems like the lens body is just one piece. But pull on the bayonet flanges of any old manual Nikonos lens and you can pull the optical block a bit out - as illustrated in the second pic above.

There are two small steel flanges inside the body which the lens kind grabs a hold off and then pulls itself towards the body by.
But I haven't yet been able to measure the offset between those steel flanges and the reference we have all been using so far (the alu flange insert). I have no idea if the optical block is designed to be pulled out by 0.25mm, 0.5mm, 1mm or even more.
But it does mean, that the shiny steel flange in the body is probably what we should really try to be our reference.

As well as the offset to the front of the alu insert in the body as explained in the previous post. The latter decides how far off the front of the internal lens block the "built in port" sits.

Probably not important on the 28/35/80mm which are flat but it may matter on the domes of the 12/15/20mm.

I Cracked It - The Real Nikonos Flange Distance! (It was there all along, though...)

Some more precise measurements and some more detective work and we are getting there.

Get ready for another ride on the topsy tervy nerdy roller coaster.
First, another correction. I stated in an earlier post that the film pressure plate should sit right up against the film plane. This is not true, I just never knew or noticed on any of my older film cameras but in fact the film pressure plate rests on rails that sit higher than the rails for the film creating clearance for the film. These are often referred to as the inner and outer film rails - the inner ones being the ones the film emulsion rests on. This will become important later on. (It also means that my own previous measurements and most everybody elses down through the throat onto the pressure plate are flawed).

Anyhow, let's get on with it.
I taped the shutter open on an older Nikonos V (in Bulb mode) and sat it on my dirty but fairly accurate CNC:

I stuck a dial test indicator on the Z-carriage so I could use the machine as a poor man's CMM (Coordinate Measuring Machine).
and yes, I was about to cut some CF plate and didn't bother to remove it for this test but the body was square and level enough;).

I decided to measure from the inner film gate rails as that's the real film plane down to the back side of the steel bayonet flange. And I think that's fair as I showed in the previous post that that's really where the locating happens for the inner spring loaded lens block.
In other words, I am measuring from the flange that's blue shaded in this rendering and then to the film plane:

(I am just not measuring the lens itself but rather the side of the steel flange that would butt up against this blue flange on the lens).

On a crappy iphone pic it looks like this - that's the back side of the steel bayonet with the DTI touching off on it:

I repeated the measurement three times and got three identical readings of 26.812mm.
And then I measured the height difference between the inner and outer rails:
And the outer rails sit 0.228mm higher than the inner rails - or 0.228mm further away from the film plane.
Which is why I say that all of us who have measured from the front of the cam to the pressure plate should really subtract 0.228mm from our measurements.

Now, this is where it gets interesting in a roundabout way. I went to an older Nikonos IV Repair Manual and lo and behold, they state a Flange Distance dimension of 27.02mm (+/- 0.04mm).
So, you would think that my 26.812mm is a bit off from that and way out of tolerance but... the repair manual states that the 27.02mm standard is "Distance from bayonet mount to outer film rail". The kicker here being the "outer film rails". In effect, their flange distance standard is not measured to the actual film plane but to the film pressure plate. I speculate because it's easier to check for a technician this way or their tool for doing so was just made that way.

Anyhow, it means I didn't follow Nikon protocol when I measured to the inner film rails and I should add the 0.228mm height offset I measured between the inner and outer rails and if we do that we get (26.812mm + 0.228mm) = 27.04mm. Which is 0.02mm from the standard but within tolerance.

BUT more importantly, it also means that for anyone wanting to do an adapter, the real number they should try to hit is ~26.8mm from the sensor to that blue shaded flange in the rendering above.

And the number was there all along, hidden in the old manuals. Not very clear as they don't show which side of the steel bayonet they measure to and there's that quirk of them not actually measuring the real flange to film plane distance.
But they even state the height delta between the inner and outer rails (though again, it's not clear they are talking height). They state 0.23mm (+/- 0.02mm) and I measured 0.228mm so I am definitely within tolerance.

Now, if we just use those numbers from the manual, they also back up my measurements as 27.02mm - 0.23mm = 26.79mm and I was at 26.812mm;)
If we play around with the stacked tolerances of both those measurements in the manual we get a range for the real flange distance of 26.73mm-26.85mm.

The last thing to settle is the exact distance from the film plane to the very front of the alu flange insert. And also how far out the lens block was designed to be pulled out of the lens housing when mounted.
For now, I speculate it's nominally 39mm to the very front and that the pull out is 1.0mm (maybe +/- 0.1mm).

Edited Monday at 12:27 PM2 days by GeckoSub

For The Visual Learners (Aren't We All)
To the best of my ability and tools, I think these are the dimensions:

And I reckon they were aiming for a 1.0mm nominal pull out of the spring loaded lens block when mounted:

Edited Monday at 01:10 PM2 days by GeckoSub

Would housing vacuum affect how far out it's pulled?

4 hours ago, Grantmac said:

Would housing vacuum affect how far out it's pulled?

Ooh, that's a good question.

I wouldn't think so as the for the vacuum to be able to pull on the inner lens block the latter would have to be sealed to the lens housing and I don't think it is. So, the vacuum can "sneak in", and can act all around it and pull in all directions and thus, it shouldn't move. At least, that's how I see it.

Edited Tuesday at 12:40 AM2 days by GeckoSub