Nikonos add-on VFs - for land use?

[retinax]

Hi all,
I've stumbled upon the add-on viewfinders for Nikonos wide-angles which seem to be plentiful, affordable and big. However some descriptions say they only work under water. Is that so? If so, how does the built-in VF of the Nikonos manage to work both under water and on land? Could an additional optical element correct for the air-water-difference?

 

[Timmyjoe]

From memory, the 20mm & 15mm Nikonos optical viewfinders only work underwater. Don't remember all the details, but water in front of the viewfinder, and the water between the back of the viewfinder and the front glass of your underwater mask, play into the optical formula of the viewfinder. I had a 20mm viewfinder and I remember it did not work out of the water.

The viewfinder built into the Nikonos V works just like a normal camera viewfinder.

Best,
-Tim

 

[d_c]

My understanding is that the Nikonos wide angle lenses - 28mm and wider - had curved front elements that relied on the different refractive index of the contacting water to be able to focus an image properly, hence they wouldn't work in the air as that 'water lens element' would be absent. I'm guessing that the viewfinders worked in a similar manner.

 

[Carey M]

The 80mm lens and its viewfinder work fine on land, but yeah, the wide stuff is useful only underwater.

 

[retinax]

Too bad. But intriguing. Can anyone explain how some lenses and viewfinders can work both in air and water, while others only in one medium?

 

[Rob-F]

The 35mm lens is supposed to work in free air.

 

[Sumarongi]

Do I suppose correctly that your plan is to have a separate wide angle finder?

If yes, one could consider to use an upwards-folding finder magnifier. I've just tested it; in my case (a Mamiya one), it gives something of a circular 17mm field of view, I guess 🙂

 

[pgk]

The Nikonos system included both underwater finders and above water ones - for the 80mm certainly but I think maybe for the 35 too(?). They also made a 28mm lens which was not for underwater use but for the 'splash' zone - and they may have made a finder for this - I can't remember although I did own this lens once. The others lenses and finders were for underwater use and the 35mm lens was indeed the widest designed for use above water. Both it and the 80mm feature an above water lens behind a flat front element (call it filter or port glass if you like). In fasct the 35mm f/2.5 Nikonos lens appears to be the same lens used on the 1950s rangefinder Nikons and was in production (fully coated) until about 2000..... .

The 28mm could apparently be used above water at very small apertures but was not good. Its front element is slightly concave if I remember correctly so it is designed for underwater use. The 15 and 20 lenses were both designed for underwater use and the 15 (I still have one as a display lens/paperweight since its effectively useless as it and the Nik5 would need an expensive service to be usable and I can't see using them) has a large domed front element so would focus only at very close distances above water - if indeed this was possible.

So 28/20/15 are unusable above water and as a consequence their viewfinders are specifically and only for underwater use.

 

[retinax]

The Nikonos system included both underwater finders and above water ones - for the 80mm certainly but I think maybe for the 35 too(?). They also made a 28mm lens which was not for underwater use but for the 'splash' zone - and they may have made a finder for this - I can't remember although I did own this lens once. The others lenses and finders were for underwater use and the 35mm lens was indeed the widest designed for use above water. Both it and the 80mm feature an above water lens behind a flat front element (call it filter or port glass if you like). In fasct the 35mm f/2.5 Nikonos lens appears to be the same lens used on the 1950s rangefinder Nikons and was in production (fully coated) until about 2000..... .

The 28mm could apparently be used above water at very small apertures but was not good. Its front element is slightly concave if I remember correctly so it is designed for underwater use. The 15 and 20 lenses were both designed for underwater use and the 15 (I still have one as a display lens/paperweight since its effectively useless as it and the Nik5 would need an expensive service to be usable and I can't see using them) has a large domed front element so would focus only at very close distances above water - if indeed this was possible.

So 28/20/15 are unusable above water and as a consequence their viewfinders are specifically and only for underwater use.

Thanks, this clears it up a bit.
Do you think it would be possible to make them useable in air with an additional element in front?